Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 1 | //===- SimplifyCFG.cpp - Code to perform CFG simplification ---------------===// |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 2 | // |
John Criswell | b576c94 | 2003-10-20 19:43:21 +0000 | [diff] [blame] | 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
Chris Lattner | 4ee451d | 2007-12-29 20:36:04 +0000 | [diff] [blame] | 5 | // This file is distributed under the University of Illinois Open Source |
| 6 | // License. See LICENSE.TXT for details. |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 7 | // |
John Criswell | b576c94 | 2003-10-20 19:43:21 +0000 | [diff] [blame] | 8 | //===----------------------------------------------------------------------===// |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 9 | // |
Chris Lattner | bb190ac | 2002-10-08 21:36:33 +0000 | [diff] [blame] | 10 | // Peephole optimize the CFG. |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
Chris Lattner | 218a822 | 2004-06-20 01:13:18 +0000 | [diff] [blame] | 14 | #define DEBUG_TYPE "simplifycfg" |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 15 | #include "llvm/Transforms/Utils/Local.h" |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 16 | #include "llvm/Constants.h" |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 17 | #include "llvm/DerivedTypes.h" |
| 18 | #include "llvm/GlobalVariable.h" |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 19 | #include "llvm/Instructions.h" |
Devang Patel | 383d7ed | 2009-02-03 22:12:02 +0000 | [diff] [blame] | 20 | #include "llvm/IntrinsicInst.h" |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 21 | #include "llvm/LLVMContext.h" |
| 22 | #include "llvm/Metadata.h" |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 23 | #include "llvm/Operator.h" |
Chris Lattner | 0d56008 | 2004-02-24 05:38:11 +0000 | [diff] [blame] | 24 | #include "llvm/Type.h" |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 25 | #include "llvm/Analysis/InstructionSimplify.h" |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 26 | #include "llvm/Analysis/ValueTracking.h" |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 27 | #include "llvm/Target/TargetData.h" |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 28 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
Dan Gohman | 2c63566 | 2009-10-30 22:39:04 +0000 | [diff] [blame] | 29 | #include "llvm/ADT/DenseMap.h" |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 30 | #include "llvm/ADT/SetVector.h" |
Chris Lattner | 93e985f | 2007-02-13 02:10:56 +0000 | [diff] [blame] | 31 | #include "llvm/ADT/SmallVector.h" |
Chris Lattner | c995123 | 2007-04-02 01:44:59 +0000 | [diff] [blame] | 32 | #include "llvm/ADT/SmallPtrSet.h" |
Evan Cheng | 502a4f5 | 2008-06-12 21:15:59 +0000 | [diff] [blame] | 33 | #include "llvm/ADT/Statistic.h" |
Chris Lattner | 6d4d21e | 2010-12-13 02:00:58 +0000 | [diff] [blame] | 34 | #include "llvm/ADT/STLExtras.h" |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 35 | #include "llvm/Support/CFG.h" |
Evan Cheng | c3f507f | 2011-01-29 04:46:23 +0000 | [diff] [blame] | 36 | #include "llvm/Support/CommandLine.h" |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 37 | #include "llvm/Support/ConstantRange.h" |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 38 | #include "llvm/Support/Debug.h" |
Devang Patel | 3e410c6 | 2011-05-18 18:01:27 +0000 | [diff] [blame] | 39 | #include "llvm/Support/IRBuilder.h" |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 40 | #include "llvm/Support/NoFolder.h" |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 41 | #include "llvm/Support/raw_ostream.h" |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 42 | #include <algorithm> |
Chris Lattner | d52c261 | 2004-02-24 07:23:58 +0000 | [diff] [blame] | 43 | #include <set> |
Chris Lattner | 698f96f | 2004-10-18 04:07:22 +0000 | [diff] [blame] | 44 | #include <map> |
Chris Lattner | f7703df | 2004-01-09 06:12:26 +0000 | [diff] [blame] | 45 | using namespace llvm; |
Brian Gaeke | d0fde30 | 2003-11-11 22:41:34 +0000 | [diff] [blame] | 46 | |
Peter Collingbourne | 57808b3 | 2011-04-29 18:47:38 +0000 | [diff] [blame] | 47 | static cl::opt<unsigned> |
| 48 | PHINodeFoldingThreshold("phi-node-folding-threshold", cl::Hidden, cl::init(1), |
| 49 | cl::desc("Control the amount of phi node folding to perform (default = 1)")); |
| 50 | |
Evan Cheng | c3f507f | 2011-01-29 04:46:23 +0000 | [diff] [blame] | 51 | static cl::opt<bool> |
| 52 | DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false), |
| 53 | cl::desc("Duplicate return instructions into unconditional branches")); |
| 54 | |
Evan Cheng | 502a4f5 | 2008-06-12 21:15:59 +0000 | [diff] [blame] | 55 | STATISTIC(NumSpeculations, "Number of speculative executed instructions"); |
| 56 | |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 57 | namespace { |
| 58 | class SimplifyCFGOpt { |
| 59 | const TargetData *const TD; |
| 60 | |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 61 | Value *isValueEqualityComparison(TerminatorInst *TI); |
| 62 | BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI, |
| 63 | std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases); |
| 64 | bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 65 | BasicBlock *Pred, |
| 66 | IRBuilder<> &Builder); |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 67 | bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI, |
| 68 | IRBuilder<> &Builder); |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 69 | |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 70 | bool SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder); |
Bill Wendling | aa5abe8 | 2012-02-06 21:16:41 +0000 | [diff] [blame] | 71 | bool SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 72 | bool SimplifyUnreachable(UnreachableInst *UI); |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 73 | bool SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 74 | bool SimplifyIndirectBr(IndirectBrInst *IBI); |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 75 | bool SimplifyUncondBranch(BranchInst *BI, IRBuilder <> &Builder); |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 76 | bool SimplifyCondBranch(BranchInst *BI, IRBuilder <>&Builder); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 77 | |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 78 | public: |
| 79 | explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {} |
| 80 | bool run(BasicBlock *BB); |
| 81 | }; |
| 82 | } |
| 83 | |
Chris Lattner | 2bdcb56 | 2005-08-03 00:19:45 +0000 | [diff] [blame] | 84 | /// SafeToMergeTerminators - Return true if it is safe to merge these two |
| 85 | /// terminator instructions together. |
| 86 | /// |
| 87 | static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) { |
| 88 | if (SI1 == SI2) return false; // Can't merge with self! |
| 89 | |
| 90 | // It is not safe to merge these two switch instructions if they have a common |
| 91 | // successor, and if that successor has a PHI node, and if *that* PHI node has |
| 92 | // conflicting incoming values from the two switch blocks. |
| 93 | BasicBlock *SI1BB = SI1->getParent(); |
| 94 | BasicBlock *SI2BB = SI2->getParent(); |
Chris Lattner | c995123 | 2007-04-02 01:44:59 +0000 | [diff] [blame] | 95 | SmallPtrSet<BasicBlock*, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB)); |
Chris Lattner | 2bdcb56 | 2005-08-03 00:19:45 +0000 | [diff] [blame] | 96 | |
| 97 | for (succ_iterator I = succ_begin(SI2BB), E = succ_end(SI2BB); I != E; ++I) |
| 98 | if (SI1Succs.count(*I)) |
| 99 | for (BasicBlock::iterator BBI = (*I)->begin(); |
| 100 | isa<PHINode>(BBI); ++BBI) { |
| 101 | PHINode *PN = cast<PHINode>(BBI); |
| 102 | if (PN->getIncomingValueForBlock(SI1BB) != |
| 103 | PN->getIncomingValueForBlock(SI2BB)) |
| 104 | return false; |
| 105 | } |
| 106 | |
| 107 | return true; |
| 108 | } |
| 109 | |
| 110 | /// AddPredecessorToBlock - Update PHI nodes in Succ to indicate that there will |
| 111 | /// now be entries in it from the 'NewPred' block. The values that will be |
| 112 | /// flowing into the PHI nodes will be the same as those coming in from |
| 113 | /// ExistPred, an existing predecessor of Succ. |
| 114 | static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred, |
| 115 | BasicBlock *ExistPred) { |
Chris Lattner | 2bdcb56 | 2005-08-03 00:19:45 +0000 | [diff] [blame] | 116 | if (!isa<PHINode>(Succ->begin())) return; // Quick exit if nothing to do |
| 117 | |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 118 | PHINode *PN; |
| 119 | for (BasicBlock::iterator I = Succ->begin(); |
| 120 | (PN = dyn_cast<PHINode>(I)); ++I) |
| 121 | PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred); |
Chris Lattner | 2bdcb56 | 2005-08-03 00:19:45 +0000 | [diff] [blame] | 122 | } |
| 123 | |
Chris Lattner | 7e66348 | 2005-08-03 00:11:16 +0000 | [diff] [blame] | 124 | |
Chris Lattner | 73c50a6 | 2010-12-14 07:00:00 +0000 | [diff] [blame] | 125 | /// GetIfCondition - Given a basic block (BB) with two predecessors (and at |
| 126 | /// least one PHI node in it), check to see if the merge at this block is due |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 127 | /// to an "if condition". If so, return the boolean condition that determines |
| 128 | /// which entry into BB will be taken. Also, return by references the block |
| 129 | /// that will be entered from if the condition is true, and the block that will |
| 130 | /// be entered if the condition is false. |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 131 | /// |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 132 | /// This does no checking to see if the true/false blocks have large or unsavory |
| 133 | /// instructions in them. |
Chris Lattner | 73c50a6 | 2010-12-14 07:00:00 +0000 | [diff] [blame] | 134 | static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, |
| 135 | BasicBlock *&IfFalse) { |
| 136 | PHINode *SomePHI = cast<PHINode>(BB->begin()); |
| 137 | assert(SomePHI->getNumIncomingValues() == 2 && |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 138 | "Function can only handle blocks with 2 predecessors!"); |
Chris Lattner | 73c50a6 | 2010-12-14 07:00:00 +0000 | [diff] [blame] | 139 | BasicBlock *Pred1 = SomePHI->getIncomingBlock(0); |
| 140 | BasicBlock *Pred2 = SomePHI->getIncomingBlock(1); |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 141 | |
| 142 | // We can only handle branches. Other control flow will be lowered to |
| 143 | // branches if possible anyway. |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 144 | BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator()); |
| 145 | BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator()); |
| 146 | if (Pred1Br == 0 || Pred2Br == 0) |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 147 | return 0; |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 148 | |
| 149 | // Eliminate code duplication by ensuring that Pred1Br is conditional if |
| 150 | // either are. |
| 151 | if (Pred2Br->isConditional()) { |
| 152 | // If both branches are conditional, we don't have an "if statement". In |
| 153 | // reality, we could transform this case, but since the condition will be |
| 154 | // required anyway, we stand no chance of eliminating it, so the xform is |
| 155 | // probably not profitable. |
| 156 | if (Pred1Br->isConditional()) |
| 157 | return 0; |
| 158 | |
| 159 | std::swap(Pred1, Pred2); |
| 160 | std::swap(Pred1Br, Pred2Br); |
| 161 | } |
| 162 | |
| 163 | if (Pred1Br->isConditional()) { |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 164 | // The only thing we have to watch out for here is to make sure that Pred2 |
| 165 | // doesn't have incoming edges from other blocks. If it does, the condition |
| 166 | // doesn't dominate BB. |
| 167 | if (Pred2->getSinglePredecessor() == 0) |
| 168 | return 0; |
| 169 | |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 170 | // If we found a conditional branch predecessor, make sure that it branches |
| 171 | // to BB and Pred2Br. If it doesn't, this isn't an "if statement". |
| 172 | if (Pred1Br->getSuccessor(0) == BB && |
| 173 | Pred1Br->getSuccessor(1) == Pred2) { |
| 174 | IfTrue = Pred1; |
| 175 | IfFalse = Pred2; |
| 176 | } else if (Pred1Br->getSuccessor(0) == Pred2 && |
| 177 | Pred1Br->getSuccessor(1) == BB) { |
| 178 | IfTrue = Pred2; |
| 179 | IfFalse = Pred1; |
| 180 | } else { |
| 181 | // We know that one arm of the conditional goes to BB, so the other must |
| 182 | // go somewhere unrelated, and this must not be an "if statement". |
| 183 | return 0; |
| 184 | } |
| 185 | |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 186 | return Pred1Br->getCondition(); |
| 187 | } |
| 188 | |
| 189 | // Ok, if we got here, both predecessors end with an unconditional branch to |
| 190 | // BB. Don't panic! If both blocks only have a single (identical) |
| 191 | // predecessor, and THAT is a conditional branch, then we're all ok! |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 192 | BasicBlock *CommonPred = Pred1->getSinglePredecessor(); |
| 193 | if (CommonPred == 0 || CommonPred != Pred2->getSinglePredecessor()) |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 194 | return 0; |
| 195 | |
| 196 | // Otherwise, if this is a conditional branch, then we can use it! |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 197 | BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator()); |
| 198 | if (BI == 0) return 0; |
| 199 | |
| 200 | assert(BI->isConditional() && "Two successors but not conditional?"); |
| 201 | if (BI->getSuccessor(0) == Pred1) { |
| 202 | IfTrue = Pred1; |
| 203 | IfFalse = Pred2; |
| 204 | } else { |
| 205 | IfTrue = Pred2; |
| 206 | IfFalse = Pred1; |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 207 | } |
Chris Lattner | 995ba1b | 2010-12-14 07:15:21 +0000 | [diff] [blame] | 208 | return BI->getCondition(); |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 209 | } |
| 210 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 211 | /// ComputeSpeculuationCost - Compute an abstract "cost" of speculating the |
| 212 | /// given instruction, which is assumed to be safe to speculate. 1 means |
| 213 | /// cheap, 2 means less cheap, and UINT_MAX means prohibitively expensive. |
| 214 | static unsigned ComputeSpeculationCost(const User *I) { |
| 215 | assert(isSafeToSpeculativelyExecute(I) && |
| 216 | "Instruction is not safe to speculatively execute!"); |
| 217 | switch (Operator::getOpcode(I)) { |
| 218 | default: |
| 219 | // In doubt, be conservative. |
| 220 | return UINT_MAX; |
| 221 | case Instruction::GetElementPtr: |
| 222 | // GEPs are cheap if all indices are constant. |
| 223 | if (!cast<GEPOperator>(I)->hasAllConstantIndices()) |
| 224 | return UINT_MAX; |
| 225 | return 1; |
| 226 | case Instruction::Load: |
| 227 | case Instruction::Add: |
| 228 | case Instruction::Sub: |
| 229 | case Instruction::And: |
| 230 | case Instruction::Or: |
| 231 | case Instruction::Xor: |
| 232 | case Instruction::Shl: |
| 233 | case Instruction::LShr: |
| 234 | case Instruction::AShr: |
| 235 | case Instruction::ICmp: |
| 236 | case Instruction::Trunc: |
| 237 | case Instruction::ZExt: |
| 238 | case Instruction::SExt: |
| 239 | return 1; // These are all cheap. |
| 240 | |
| 241 | case Instruction::Call: |
| 242 | case Instruction::Select: |
| 243 | return 2; |
| 244 | } |
| 245 | } |
| 246 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 247 | /// DominatesMergePoint - If we have a merge point of an "if condition" as |
| 248 | /// accepted above, return true if the specified value dominates the block. We |
| 249 | /// don't handle the true generality of domination here, just a special case |
| 250 | /// which works well enough for us. |
| 251 | /// |
| 252 | /// If AggressiveInsts is non-null, and if V does not dominate BB, we check to |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 253 | /// see if V (which must be an instruction) and its recursive operands |
| 254 | /// that do not dominate BB have a combined cost lower than CostRemaining and |
| 255 | /// are non-trapping. If both are true, the instruction is inserted into the |
| 256 | /// set and true is returned. |
| 257 | /// |
| 258 | /// The cost for most non-trapping instructions is defined as 1 except for |
| 259 | /// Select whose cost is 2. |
| 260 | /// |
| 261 | /// After this function returns, CostRemaining is decreased by the cost of |
| 262 | /// V plus its non-dominating operands. If that cost is greater than |
| 263 | /// CostRemaining, false is returned and CostRemaining is undefined. |
Chris Lattner | 9c07866 | 2004-10-14 05:13:36 +0000 | [diff] [blame] | 264 | static bool DominatesMergePoint(Value *V, BasicBlock *BB, |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 265 | SmallPtrSet<Instruction*, 4> *AggressiveInsts, |
| 266 | unsigned &CostRemaining) { |
Chris Lattner | 570751c | 2004-04-09 22:50:22 +0000 | [diff] [blame] | 267 | Instruction *I = dyn_cast<Instruction>(V); |
Chris Lattner | b74b181 | 2006-10-20 00:42:07 +0000 | [diff] [blame] | 268 | if (!I) { |
| 269 | // Non-instructions all dominate instructions, but not all constantexprs |
| 270 | // can be executed unconditionally. |
| 271 | if (ConstantExpr *C = dyn_cast<ConstantExpr>(V)) |
| 272 | if (C->canTrap()) |
| 273 | return false; |
| 274 | return true; |
| 275 | } |
Chris Lattner | 570751c | 2004-04-09 22:50:22 +0000 | [diff] [blame] | 276 | BasicBlock *PBB = I->getParent(); |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 277 | |
Chris Lattner | da895d6 | 2005-02-27 06:18:25 +0000 | [diff] [blame] | 278 | // We don't want to allow weird loops that might have the "if condition" in |
Chris Lattner | 570751c | 2004-04-09 22:50:22 +0000 | [diff] [blame] | 279 | // the bottom of this block. |
| 280 | if (PBB == BB) return false; |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 281 | |
Chris Lattner | 570751c | 2004-04-09 22:50:22 +0000 | [diff] [blame] | 282 | // If this instruction is defined in a block that contains an unconditional |
| 283 | // branch to BB, then it must be in the 'conditional' part of the "if |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 284 | // statement". If not, it definitely dominates the region. |
| 285 | BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator()); |
| 286 | if (BI == 0 || BI->isConditional() || BI->getSuccessor(0) != BB) |
| 287 | return true; |
Eli Friedman | 0b79a77 | 2009-07-17 04:28:42 +0000 | [diff] [blame] | 288 | |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 289 | // If we aren't allowing aggressive promotion anymore, then don't consider |
| 290 | // instructions in the 'if region'. |
| 291 | if (AggressiveInsts == 0) return false; |
| 292 | |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 293 | // If we have seen this instruction before, don't count it again. |
| 294 | if (AggressiveInsts->count(I)) return true; |
| 295 | |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 296 | // Okay, it looks like the instruction IS in the "condition". Check to |
| 297 | // see if it's a cheap instruction to unconditionally compute, and if it |
| 298 | // only uses stuff defined outside of the condition. If so, hoist it out. |
Dan Gohman | f042660 | 2011-12-14 23:49:11 +0000 | [diff] [blame] | 299 | if (!isSafeToSpeculativelyExecute(I)) |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 300 | return false; |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 301 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 302 | unsigned Cost = ComputeSpeculationCost(I); |
Chris Lattner | 570751c | 2004-04-09 22:50:22 +0000 | [diff] [blame] | 303 | |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 304 | if (Cost > CostRemaining) |
| 305 | return false; |
| 306 | |
| 307 | CostRemaining -= Cost; |
| 308 | |
| 309 | // Okay, we can only really hoist these out if their operands do |
| 310 | // not take us over the cost threshold. |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 311 | for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 312 | if (!DominatesMergePoint(*i, BB, AggressiveInsts, CostRemaining)) |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 313 | return false; |
| 314 | // Okay, it's safe to do this! Remember this instruction. |
| 315 | AggressiveInsts->insert(I); |
Chris Lattner | 723c66d | 2004-02-11 03:36:04 +0000 | [diff] [blame] | 316 | return true; |
| 317 | } |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 318 | |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 319 | /// GetConstantInt - Extract ConstantInt from value, looking through IntToPtr |
| 320 | /// and PointerNullValue. Return NULL if value is not a constant int. |
Chris Lattner | 28acc13 | 2010-12-13 03:30:12 +0000 | [diff] [blame] | 321 | static ConstantInt *GetConstantInt(Value *V, const TargetData *TD) { |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 322 | // Normal constant int. |
| 323 | ConstantInt *CI = dyn_cast<ConstantInt>(V); |
Duncan Sands | 1df9859 | 2010-02-16 11:11:14 +0000 | [diff] [blame] | 324 | if (CI || !TD || !isa<Constant>(V) || !V->getType()->isPointerTy()) |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 325 | return CI; |
| 326 | |
| 327 | // This is some kind of pointer constant. Turn it into a pointer-sized |
| 328 | // ConstantInt if possible. |
Chris Lattner | db125cf | 2011-07-18 04:54:35 +0000 | [diff] [blame] | 329 | IntegerType *PtrTy = TD->getIntPtrType(V->getContext()); |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 330 | |
| 331 | // Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*). |
| 332 | if (isa<ConstantPointerNull>(V)) |
| 333 | return ConstantInt::get(PtrTy, 0); |
| 334 | |
| 335 | // IntToPtr const int. |
| 336 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) |
| 337 | if (CE->getOpcode() == Instruction::IntToPtr) |
| 338 | if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(0))) { |
| 339 | // The constant is very likely to have the right type already. |
| 340 | if (CI->getType() == PtrTy) |
| 341 | return CI; |
| 342 | else |
| 343 | return cast<ConstantInt> |
| 344 | (ConstantExpr::getIntegerCast(CI, PtrTy, /*isSigned=*/false)); |
| 345 | } |
| 346 | return 0; |
| 347 | } |
| 348 | |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 349 | /// GatherConstantCompares - Given a potentially 'or'd or 'and'd together |
| 350 | /// collection of icmp eq/ne instructions that compare a value against a |
| 351 | /// constant, return the value being compared, and stick the constant into the |
| 352 | /// Values vector. |
Chris Lattner | 28acc13 | 2010-12-13 03:30:12 +0000 | [diff] [blame] | 353 | static Value * |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 354 | GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 355 | const TargetData *TD, bool isEQ, unsigned &UsedICmps) { |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 356 | Instruction *I = dyn_cast<Instruction>(V); |
| 357 | if (I == 0) return 0; |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 358 | |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 359 | // If this is an icmp against a constant, handle this as one of the cases. |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 360 | if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) { |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 361 | if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) { |
| 362 | if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) { |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 363 | UsedICmps++; |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 364 | Vals.push_back(C); |
| 365 | return I->getOperand(0); |
| 366 | } |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 367 | |
| 368 | // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to |
| 369 | // the set. |
| 370 | ConstantRange Span = |
Chris Lattner | a37029c | 2010-12-18 20:22:49 +0000 | [diff] [blame] | 371 | ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue()); |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 372 | |
| 373 | // If this is an and/!= check then we want to optimize "x ugt 2" into |
| 374 | // x != 0 && x != 1. |
| 375 | if (!isEQ) |
| 376 | Span = Span.inverse(); |
| 377 | |
| 378 | // If there are a ton of values, we don't want to make a ginormous switch. |
Nick Lewycky | f460bf8 | 2012-01-19 18:19:42 +0000 | [diff] [blame] | 379 | if (Span.getSetSize().ugt(8) || Span.isEmptySet()) |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 380 | return 0; |
| 381 | |
| 382 | for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp) |
| 383 | Vals.push_back(ConstantInt::get(V->getContext(), Tmp)); |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 384 | UsedICmps++; |
Chris Lattner | e27db74 | 2010-12-17 06:20:15 +0000 | [diff] [blame] | 385 | return I->getOperand(0); |
| 386 | } |
Chris Lattner | 662269d | 2010-12-13 04:18:32 +0000 | [diff] [blame] | 387 | return 0; |
| 388 | } |
| 389 | |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 390 | // Otherwise, we can only handle an | or &, depending on isEQ. |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 391 | if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And)) |
Chris Lattner | 662269d | 2010-12-13 04:18:32 +0000 | [diff] [blame] | 392 | return 0; |
Chris Lattner | 662269d | 2010-12-13 04:18:32 +0000 | [diff] [blame] | 393 | |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 394 | unsigned NumValsBeforeLHS = Vals.size(); |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 395 | unsigned UsedICmpsBeforeLHS = UsedICmps; |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 396 | if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD, |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 397 | isEQ, UsedICmps)) { |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 398 | unsigned NumVals = Vals.size(); |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 399 | unsigned UsedICmpsBeforeRHS = UsedICmps; |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 400 | if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD, |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 401 | isEQ, UsedICmps)) { |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 402 | if (LHS == RHS) |
| 403 | return LHS; |
Chris Lattner | 92407e5 | 2010-12-13 07:41:29 +0000 | [diff] [blame] | 404 | Vals.resize(NumVals); |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 405 | UsedICmps = UsedICmpsBeforeRHS; |
Chris Lattner | 0aa749b | 2010-12-13 04:26:26 +0000 | [diff] [blame] | 406 | } |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 407 | |
| 408 | // The RHS of the or/and can't be folded in and we haven't used "Extra" yet, |
| 409 | // set it and return success. |
| 410 | if (Extra == 0 || Extra == I->getOperand(1)) { |
| 411 | Extra = I->getOperand(1); |
| 412 | return LHS; |
| 413 | } |
| 414 | |
| 415 | Vals.resize(NumValsBeforeLHS); |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 416 | UsedICmps = UsedICmpsBeforeLHS; |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 417 | return 0; |
Anton Korobeynikov | 07e6e56 | 2008-02-20 11:26:25 +0000 | [diff] [blame] | 418 | } |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 419 | |
| 420 | // If the LHS can't be folded in, but Extra is available and RHS can, try to |
| 421 | // use LHS as Extra. |
| 422 | if (Extra == 0 || Extra == I->getOperand(0)) { |
Chris Lattner | 92407e5 | 2010-12-13 07:41:29 +0000 | [diff] [blame] | 423 | Value *OldExtra = Extra; |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 424 | Extra = I->getOperand(0); |
| 425 | if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD, |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 426 | isEQ, UsedICmps)) |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 427 | return RHS; |
Chris Lattner | 92407e5 | 2010-12-13 07:41:29 +0000 | [diff] [blame] | 428 | assert(Vals.size() == NumValsBeforeLHS); |
| 429 | Extra = OldExtra; |
Chris Lattner | 7312a22 | 2010-12-13 04:50:38 +0000 | [diff] [blame] | 430 | } |
| 431 | |
Chris Lattner | 0d56008 | 2004-02-24 05:38:11 +0000 | [diff] [blame] | 432 | return 0; |
| 433 | } |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 434 | |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 435 | static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) { |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 436 | Instruction *Cond = 0; |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 437 | if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
| 438 | Cond = dyn_cast<Instruction>(SI->getCondition()); |
| 439 | } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { |
| 440 | if (BI->isConditional()) |
| 441 | Cond = dyn_cast<Instruction>(BI->getCondition()); |
Frits van Bommel | 7ac40c3 | 2010-12-05 18:29:03 +0000 | [diff] [blame] | 442 | } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(TI)) { |
| 443 | Cond = dyn_cast<Instruction>(IBI->getAddress()); |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 444 | } |
| 445 | |
| 446 | TI->eraseFromParent(); |
| 447 | if (Cond) RecursivelyDeleteTriviallyDeadInstructions(Cond); |
| 448 | } |
| 449 | |
Chris Lattner | 9fd4955 | 2008-11-27 23:25:44 +0000 | [diff] [blame] | 450 | /// isValueEqualityComparison - Return true if the specified terminator checks |
| 451 | /// to see if a value is equal to constant integer value. |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 452 | Value *SimplifyCFGOpt::isValueEqualityComparison(TerminatorInst *TI) { |
| 453 | Value *CV = 0; |
Chris Lattner | 4bebf08 | 2004-03-16 19:45:22 +0000 | [diff] [blame] | 454 | if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
| 455 | // Do not permit merging of large switch instructions into their |
| 456 | // predecessors unless there is only one predecessor. |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 457 | if (SI->getNumSuccessors()*std::distance(pred_begin(SI->getParent()), |
| 458 | pred_end(SI->getParent())) <= 128) |
| 459 | CV = SI->getCondition(); |
| 460 | } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 461 | if (BI->isConditional() && BI->getCondition()->hasOneUse()) |
Reid Spencer | e4d87aa | 2006-12-23 06:05:41 +0000 | [diff] [blame] | 462 | if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) |
| 463 | if ((ICI->getPredicate() == ICmpInst::ICMP_EQ || |
| 464 | ICI->getPredicate() == ICmpInst::ICMP_NE) && |
Chris Lattner | 28acc13 | 2010-12-13 03:30:12 +0000 | [diff] [blame] | 465 | GetConstantInt(ICI->getOperand(1), TD)) |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 466 | CV = ICI->getOperand(0); |
| 467 | |
| 468 | // Unwrap any lossless ptrtoint cast. |
| 469 | if (TD && CV && CV->getType() == TD->getIntPtrType(CV->getContext())) |
| 470 | if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV)) |
| 471 | CV = PTII->getOperand(0); |
| 472 | return CV; |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 473 | } |
| 474 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 475 | /// GetValueEqualityComparisonCases - Given a value comparison instruction, |
| 476 | /// decode all of the 'cases' that it represents and return the 'default' block. |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 477 | BasicBlock *SimplifyCFGOpt:: |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 478 | GetValueEqualityComparisonCases(TerminatorInst *TI, |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 479 | std::vector<std::pair<ConstantInt*, |
| 480 | BasicBlock*> > &Cases) { |
| 481 | if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
| 482 | Cases.reserve(SI->getNumCases()); |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 483 | for (SwitchInst::CaseIt i = SI->caseBegin(), e = SI->caseEnd(); i != e; ++i) |
| 484 | Cases.push_back(std::make_pair(i.getCaseValue(), |
| 485 | i.getCaseSuccessor())); |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 486 | return SI->getDefaultDest(); |
| 487 | } |
| 488 | |
| 489 | BranchInst *BI = cast<BranchInst>(TI); |
Reid Spencer | e4d87aa | 2006-12-23 06:05:41 +0000 | [diff] [blame] | 490 | ICmpInst *ICI = cast<ICmpInst>(BI->getCondition()); |
Chris Lattner | 28acc13 | 2010-12-13 03:30:12 +0000 | [diff] [blame] | 491 | Cases.push_back(std::make_pair(GetConstantInt(ICI->getOperand(1), TD), |
Reid Spencer | e4d87aa | 2006-12-23 06:05:41 +0000 | [diff] [blame] | 492 | BI->getSuccessor(ICI->getPredicate() == |
| 493 | ICmpInst::ICMP_NE))); |
| 494 | return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ); |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 495 | } |
| 496 | |
| 497 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 498 | /// EliminateBlockCases - Given a vector of bb/value pairs, remove any entries |
| 499 | /// in the list that match the specified block. |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 500 | static void EliminateBlockCases(BasicBlock *BB, |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 501 | std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases) { |
| 502 | for (unsigned i = 0, e = Cases.size(); i != e; ++i) |
| 503 | if (Cases[i].second == BB) { |
| 504 | Cases.erase(Cases.begin()+i); |
| 505 | --i; --e; |
| 506 | } |
| 507 | } |
| 508 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 509 | /// ValuesOverlap - Return true if there are any keys in C1 that exist in C2 as |
| 510 | /// well. |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 511 | static bool |
| 512 | ValuesOverlap(std::vector<std::pair<ConstantInt*, BasicBlock*> > &C1, |
| 513 | std::vector<std::pair<ConstantInt*, BasicBlock*> > &C2) { |
| 514 | std::vector<std::pair<ConstantInt*, BasicBlock*> > *V1 = &C1, *V2 = &C2; |
| 515 | |
| 516 | // Make V1 be smaller than V2. |
| 517 | if (V1->size() > V2->size()) |
| 518 | std::swap(V1, V2); |
| 519 | |
| 520 | if (V1->size() == 0) return false; |
| 521 | if (V1->size() == 1) { |
| 522 | // Just scan V2. |
| 523 | ConstantInt *TheVal = (*V1)[0].first; |
| 524 | for (unsigned i = 0, e = V2->size(); i != e; ++i) |
| 525 | if (TheVal == (*V2)[i].first) |
| 526 | return true; |
| 527 | } |
| 528 | |
| 529 | // Otherwise, just sort both lists and compare element by element. |
Chris Lattner | fca20f5 | 2010-12-13 03:24:30 +0000 | [diff] [blame] | 530 | array_pod_sort(V1->begin(), V1->end()); |
| 531 | array_pod_sort(V2->begin(), V2->end()); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 532 | unsigned i1 = 0, i2 = 0, e1 = V1->size(), e2 = V2->size(); |
| 533 | while (i1 != e1 && i2 != e2) { |
| 534 | if ((*V1)[i1].first == (*V2)[i2].first) |
| 535 | return true; |
| 536 | if ((*V1)[i1].first < (*V2)[i2].first) |
| 537 | ++i1; |
| 538 | else |
| 539 | ++i2; |
| 540 | } |
| 541 | return false; |
| 542 | } |
| 543 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 544 | /// SimplifyEqualityComparisonWithOnlyPredecessor - If TI is known to be a |
| 545 | /// terminator instruction and its block is known to only have a single |
| 546 | /// predecessor block, check to see if that predecessor is also a value |
| 547 | /// comparison with the same value, and if that comparison determines the |
| 548 | /// outcome of this comparison. If so, simplify TI. This does a very limited |
| 549 | /// form of jump threading. |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 550 | bool SimplifyCFGOpt:: |
| 551 | SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 552 | BasicBlock *Pred, |
| 553 | IRBuilder<> &Builder) { |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 554 | Value *PredVal = isValueEqualityComparison(Pred->getTerminator()); |
| 555 | if (!PredVal) return false; // Not a value comparison in predecessor. |
| 556 | |
| 557 | Value *ThisVal = isValueEqualityComparison(TI); |
| 558 | assert(ThisVal && "This isn't a value comparison!!"); |
| 559 | if (ThisVal != PredVal) return false; // Different predicates. |
| 560 | |
| 561 | // Find out information about when control will move from Pred to TI's block. |
| 562 | std::vector<std::pair<ConstantInt*, BasicBlock*> > PredCases; |
| 563 | BasicBlock *PredDef = GetValueEqualityComparisonCases(Pred->getTerminator(), |
| 564 | PredCases); |
| 565 | EliminateBlockCases(PredDef, PredCases); // Remove default from cases. |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 566 | |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 567 | // Find information about how control leaves this block. |
| 568 | std::vector<std::pair<ConstantInt*, BasicBlock*> > ThisCases; |
| 569 | BasicBlock *ThisDef = GetValueEqualityComparisonCases(TI, ThisCases); |
| 570 | EliminateBlockCases(ThisDef, ThisCases); // Remove default from cases. |
| 571 | |
| 572 | // If TI's block is the default block from Pred's comparison, potentially |
| 573 | // simplify TI based on this knowledge. |
| 574 | if (PredDef == TI->getParent()) { |
| 575 | // If we are here, we know that the value is none of those cases listed in |
| 576 | // PredCases. If there are any cases in ThisCases that are in PredCases, we |
| 577 | // can simplify TI. |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 578 | if (!ValuesOverlap(PredCases, ThisCases)) |
| 579 | return false; |
| 580 | |
| 581 | if (isa<BranchInst>(TI)) { |
| 582 | // Okay, one of the successors of this condbr is dead. Convert it to a |
| 583 | // uncond br. |
| 584 | assert(ThisCases.size() == 1 && "Branch can only have one case!"); |
| 585 | // Insert the new branch. |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 586 | Instruction *NI = Builder.CreateBr(ThisDef); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 587 | (void) NI; |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 588 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 589 | // Remove PHI node entries for the dead edge. |
| 590 | ThisCases[0].second->removePredecessor(TI->getParent()); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 591 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 592 | DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator() |
| 593 | << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n"); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 594 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 595 | EraseTerminatorInstAndDCECond(TI); |
| 596 | return true; |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 597 | } |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 598 | |
| 599 | SwitchInst *SI = cast<SwitchInst>(TI); |
| 600 | // Okay, TI has cases that are statically dead, prune them away. |
| 601 | SmallPtrSet<Constant*, 16> DeadCases; |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 602 | for (unsigned i = 0, e = PredCases.size(); i != e; ++i) |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 603 | DeadCases.insert(PredCases[i].first); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 604 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 605 | DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator() |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 606 | << "Through successor TI: " << *TI); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 607 | |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 608 | for (SwitchInst::CaseIt i = SI->caseEnd(), e = SI->caseBegin(); i != e;) { |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 609 | --i; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 610 | if (DeadCases.count(i.getCaseValue())) { |
| 611 | i.getCaseSuccessor()->removePredecessor(TI->getParent()); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 612 | SI->removeCase(i); |
| 613 | } |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 614 | } |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 615 | |
| 616 | DEBUG(dbgs() << "Leaving: " << *TI << "\n"); |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 617 | return true; |
| 618 | } |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 619 | |
| 620 | // Otherwise, TI's block must correspond to some matched value. Find out |
| 621 | // which value (or set of values) this is. |
| 622 | ConstantInt *TIV = 0; |
| 623 | BasicBlock *TIBB = TI->getParent(); |
| 624 | for (unsigned i = 0, e = PredCases.size(); i != e; ++i) |
| 625 | if (PredCases[i].second == TIBB) { |
| 626 | if (TIV != 0) |
| 627 | return false; // Cannot handle multiple values coming to this block. |
| 628 | TIV = PredCases[i].first; |
| 629 | } |
| 630 | assert(TIV && "No edge from pred to succ?"); |
| 631 | |
| 632 | // Okay, we found the one constant that our value can be if we get into TI's |
| 633 | // BB. Find out which successor will unconditionally be branched to. |
| 634 | BasicBlock *TheRealDest = 0; |
| 635 | for (unsigned i = 0, e = ThisCases.size(); i != e; ++i) |
| 636 | if (ThisCases[i].first == TIV) { |
| 637 | TheRealDest = ThisCases[i].second; |
| 638 | break; |
| 639 | } |
| 640 | |
| 641 | // If not handled by any explicit cases, it is handled by the default case. |
| 642 | if (TheRealDest == 0) TheRealDest = ThisDef; |
| 643 | |
| 644 | // Remove PHI node entries for dead edges. |
| 645 | BasicBlock *CheckEdge = TheRealDest; |
| 646 | for (succ_iterator SI = succ_begin(TIBB), e = succ_end(TIBB); SI != e; ++SI) |
| 647 | if (*SI != CheckEdge) |
| 648 | (*SI)->removePredecessor(TIBB); |
| 649 | else |
| 650 | CheckEdge = 0; |
| 651 | |
| 652 | // Insert the new branch. |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 653 | Instruction *NI = Builder.CreateBr(TheRealDest); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 654 | (void) NI; |
| 655 | |
| 656 | DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator() |
| 657 | << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n"); |
| 658 | |
| 659 | EraseTerminatorInstAndDCECond(TI); |
| 660 | return true; |
Chris Lattner | 623369a | 2005-02-24 06:17:52 +0000 | [diff] [blame] | 661 | } |
| 662 | |
Dale Johannesen | c81f544 | 2009-03-12 21:01:11 +0000 | [diff] [blame] | 663 | namespace { |
| 664 | /// ConstantIntOrdering - This class implements a stable ordering of constant |
| 665 | /// integers that does not depend on their address. This is important for |
| 666 | /// applications that sort ConstantInt's to ensure uniqueness. |
| 667 | struct ConstantIntOrdering { |
| 668 | bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const { |
| 669 | return LHS->getValue().ult(RHS->getValue()); |
| 670 | } |
| 671 | }; |
| 672 | } |
Dale Johannesen | a9537cf | 2009-03-12 01:00:26 +0000 | [diff] [blame] | 673 | |
Chris Lattner | 6d4d21e | 2010-12-13 02:00:58 +0000 | [diff] [blame] | 674 | static int ConstantIntSortPredicate(const void *P1, const void *P2) { |
| 675 | const ConstantInt *LHS = *(const ConstantInt**)P1; |
| 676 | const ConstantInt *RHS = *(const ConstantInt**)P2; |
Chris Lattner | ba3c815 | 2010-12-15 04:52:41 +0000 | [diff] [blame] | 677 | if (LHS->getValue().ult(RHS->getValue())) |
| 678 | return 1; |
| 679 | if (LHS->getValue() == RHS->getValue()) |
| 680 | return 0; |
| 681 | return -1; |
Chris Lattner | 6d4d21e | 2010-12-13 02:00:58 +0000 | [diff] [blame] | 682 | } |
| 683 | |
Bill Wendling | 5049fa6 | 2009-01-19 23:43:56 +0000 | [diff] [blame] | 684 | /// FoldValueComparisonIntoPredecessors - The specified terminator is a value |
| 685 | /// equality comparison instruction (either a switch or a branch on "X == c"). |
| 686 | /// See if any of the predecessors of the terminator block are value comparisons |
| 687 | /// on the same value. If so, and if safe to do so, fold them together. |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 688 | bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, |
| 689 | IRBuilder<> &Builder) { |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 690 | BasicBlock *BB = TI->getParent(); |
| 691 | Value *CV = isValueEqualityComparison(TI); // CondVal |
| 692 | assert(CV && "Not a comparison?"); |
| 693 | bool Changed = false; |
| 694 | |
Chris Lattner | 8244243 | 2008-02-18 07:42:56 +0000 | [diff] [blame] | 695 | SmallVector<BasicBlock*, 16> Preds(pred_begin(BB), pred_end(BB)); |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 696 | while (!Preds.empty()) { |
Dan Gohman | e9d87f4 | 2009-05-06 17:22:41 +0000 | [diff] [blame] | 697 | BasicBlock *Pred = Preds.pop_back_val(); |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 698 | |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 699 | // See if the predecessor is a comparison with the same value. |
| 700 | TerminatorInst *PTI = Pred->getTerminator(); |
| 701 | Value *PCV = isValueEqualityComparison(PTI); // PredCondVal |
| 702 | |
| 703 | if (PCV == CV && SafeToMergeTerminators(TI, PTI)) { |
| 704 | // Figure out which 'cases' to copy from SI to PSI. |
| 705 | std::vector<std::pair<ConstantInt*, BasicBlock*> > BBCases; |
| 706 | BasicBlock *BBDefault = GetValueEqualityComparisonCases(TI, BBCases); |
| 707 | |
| 708 | std::vector<std::pair<ConstantInt*, BasicBlock*> > PredCases; |
| 709 | BasicBlock *PredDefault = GetValueEqualityComparisonCases(PTI, PredCases); |
| 710 | |
| 711 | // Based on whether the default edge from PTI goes to BB or not, fill in |
| 712 | // PredCases and PredDefault with the new switch cases we would like to |
| 713 | // build. |
Chris Lattner | 8244243 | 2008-02-18 07:42:56 +0000 | [diff] [blame] | 714 | SmallVector<BasicBlock*, 8> NewSuccessors; |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 715 | |
| 716 | if (PredDefault == BB) { |
| 717 | // If this is the default destination from PTI, only the edges in TI |
| 718 | // that don't occur in PTI, or that branch to BB will be activated. |
Dale Johannesen | c81f544 | 2009-03-12 21:01:11 +0000 | [diff] [blame] | 719 | std::set<ConstantInt*, ConstantIntOrdering> PTIHandled; |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 720 | for (unsigned i = 0, e = PredCases.size(); i != e; ++i) |
| 721 | if (PredCases[i].second != BB) |
| 722 | PTIHandled.insert(PredCases[i].first); |
| 723 | else { |
| 724 | // The default destination is BB, we don't need explicit targets. |
| 725 | std::swap(PredCases[i], PredCases.back()); |
| 726 | PredCases.pop_back(); |
| 727 | --i; --e; |
| 728 | } |
| 729 | |
| 730 | // Reconstruct the new switch statement we will be building. |
| 731 | if (PredDefault != BBDefault) { |
| 732 | PredDefault->removePredecessor(Pred); |
| 733 | PredDefault = BBDefault; |
| 734 | NewSuccessors.push_back(BBDefault); |
| 735 | } |
| 736 | for (unsigned i = 0, e = BBCases.size(); i != e; ++i) |
| 737 | if (!PTIHandled.count(BBCases[i].first) && |
| 738 | BBCases[i].second != BBDefault) { |
| 739 | PredCases.push_back(BBCases[i]); |
| 740 | NewSuccessors.push_back(BBCases[i].second); |
| 741 | } |
| 742 | |
| 743 | } else { |
| 744 | // If this is not the default destination from PSI, only the edges |
| 745 | // in SI that occur in PSI with a destination of BB will be |
| 746 | // activated. |
Dale Johannesen | c81f544 | 2009-03-12 21:01:11 +0000 | [diff] [blame] | 747 | std::set<ConstantInt*, ConstantIntOrdering> PTIHandled; |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 748 | for (unsigned i = 0, e = PredCases.size(); i != e; ++i) |
| 749 | if (PredCases[i].second == BB) { |
| 750 | PTIHandled.insert(PredCases[i].first); |
| 751 | std::swap(PredCases[i], PredCases.back()); |
| 752 | PredCases.pop_back(); |
| 753 | --i; --e; |
| 754 | } |
| 755 | |
| 756 | // Okay, now we know which constants were sent to BB from the |
| 757 | // predecessor. Figure out where they will all go now. |
| 758 | for (unsigned i = 0, e = BBCases.size(); i != e; ++i) |
| 759 | if (PTIHandled.count(BBCases[i].first)) { |
| 760 | // If this is one we are capable of getting... |
| 761 | PredCases.push_back(BBCases[i]); |
| 762 | NewSuccessors.push_back(BBCases[i].second); |
| 763 | PTIHandled.erase(BBCases[i].first);// This constant is taken care of |
| 764 | } |
| 765 | |
| 766 | // If there are any constants vectored to BB that TI doesn't handle, |
| 767 | // they must go to the default destination of TI. |
Dale Johannesen | c81f544 | 2009-03-12 21:01:11 +0000 | [diff] [blame] | 768 | for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I = |
| 769 | PTIHandled.begin(), |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 770 | E = PTIHandled.end(); I != E; ++I) { |
| 771 | PredCases.push_back(std::make_pair(*I, BBDefault)); |
| 772 | NewSuccessors.push_back(BBDefault); |
| 773 | } |
| 774 | } |
| 775 | |
| 776 | // Okay, at this point, we know which new successor Pred will get. Make |
| 777 | // sure we update the number of entries in the PHI nodes for these |
| 778 | // successors. |
| 779 | for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i) |
| 780 | AddPredecessorToBlock(NewSuccessors[i], Pred, BB); |
| 781 | |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 782 | Builder.SetInsertPoint(PTI); |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 783 | // Convert pointer to int before we switch. |
Duncan Sands | 1df9859 | 2010-02-16 11:11:14 +0000 | [diff] [blame] | 784 | if (CV->getType()->isPointerTy()) { |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 785 | assert(TD && "Cannot switch on pointer without TargetData"); |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 786 | CV = Builder.CreatePtrToInt(CV, TD->getIntPtrType(CV->getContext()), |
| 787 | "magicptr"); |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 788 | } |
| 789 | |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 790 | // Now that the successors are updated, create the new Switch instruction. |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 791 | SwitchInst *NewSI = Builder.CreateSwitch(CV, PredDefault, |
| 792 | PredCases.size()); |
Devang Patel | d80e8ed | 2011-05-17 23:29:05 +0000 | [diff] [blame] | 793 | NewSI->setDebugLoc(PTI->getDebugLoc()); |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 794 | for (unsigned i = 0, e = PredCases.size(); i != e; ++i) |
| 795 | NewSI->addCase(PredCases[i].first, PredCases[i].second); |
Chris Lattner | 13b2f76 | 2005-01-01 16:02:12 +0000 | [diff] [blame] | 796 | |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 797 | EraseTerminatorInstAndDCECond(PTI); |
Chris Lattner | 13b2f76 | 2005-01-01 16:02:12 +0000 | [diff] [blame] | 798 | |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 799 | // Okay, last check. If BB is still a successor of PSI, then we must |
| 800 | // have an infinite loop case. If so, add an infinitely looping block |
| 801 | // to handle the case to preserve the behavior of the code. |
| 802 | BasicBlock *InfLoopBlock = 0; |
| 803 | for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i) |
| 804 | if (NewSI->getSuccessor(i) == BB) { |
| 805 | if (InfLoopBlock == 0) { |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 806 | // Insert it at the end of the function, because it's either code, |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 807 | // or it won't matter if it's hot. :) |
Owen Anderson | 1d0be15 | 2009-08-13 21:58:54 +0000 | [diff] [blame] | 808 | InfLoopBlock = BasicBlock::Create(BB->getContext(), |
| 809 | "infloop", BB->getParent()); |
Gabor Greif | 051a950 | 2008-04-06 20:25:17 +0000 | [diff] [blame] | 810 | BranchInst::Create(InfLoopBlock, InfLoopBlock); |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 811 | } |
| 812 | NewSI->setSuccessor(i, InfLoopBlock); |
| 813 | } |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 814 | |
Chris Lattner | 542f149 | 2004-02-28 21:28:10 +0000 | [diff] [blame] | 815 | Changed = true; |
| 816 | } |
| 817 | } |
| 818 | return Changed; |
| 819 | } |
| 820 | |
Dale Johannesen | c1f1040 | 2009-06-15 20:59:27 +0000 | [diff] [blame] | 821 | // isSafeToHoistInvoke - If we would need to insert a select that uses the |
| 822 | // value of this invoke (comments in HoistThenElseCodeToIf explain why we |
| 823 | // would need to do this), we can't hoist the invoke, as there is nowhere |
| 824 | // to put the select in this case. |
| 825 | static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2, |
| 826 | Instruction *I1, Instruction *I2) { |
| 827 | for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) { |
| 828 | PHINode *PN; |
| 829 | for (BasicBlock::iterator BBI = SI->begin(); |
| 830 | (PN = dyn_cast<PHINode>(BBI)); ++BBI) { |
| 831 | Value *BB1V = PN->getIncomingValueForBlock(BB1); |
| 832 | Value *BB2V = PN->getIncomingValueForBlock(BB2); |
| 833 | if (BB1V != BB2V && (BB1V==I1 || BB2V==I2)) { |
| 834 | return false; |
| 835 | } |
| 836 | } |
| 837 | } |
| 838 | return true; |
| 839 | } |
| 840 | |
Chris Lattner | 6306d07 | 2005-08-03 17:59:45 +0000 | [diff] [blame] | 841 | /// HoistThenElseCodeToIf - Given a conditional branch that goes to BB1 and |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 842 | /// BB2, hoist any common code in the two blocks up into the branch block. The |
| 843 | /// caller of this function guarantees that BI's block dominates BB1 and BB2. |
Rafael Espindola | 216dde9 | 2011-05-19 02:26:30 +0000 | [diff] [blame] | 844 | static bool HoistThenElseCodeToIf(BranchInst *BI) { |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 845 | // This does very trivial matching, with limited scanning, to find identical |
| 846 | // instructions in the two blocks. In particular, we don't want to get into |
| 847 | // O(M*N) situations here where M and N are the sizes of BB1 and BB2. As |
| 848 | // such, we currently just scan for obviously identical instructions in an |
| 849 | // identical order. |
| 850 | BasicBlock *BB1 = BI->getSuccessor(0); // The true destination. |
| 851 | BasicBlock *BB2 = BI->getSuccessor(1); // The false destination |
| 852 | |
Devang Patel | 65085cf | 2009-02-04 00:03:08 +0000 | [diff] [blame] | 853 | BasicBlock::iterator BB1_Itr = BB1->begin(); |
| 854 | BasicBlock::iterator BB2_Itr = BB2->begin(); |
| 855 | |
| 856 | Instruction *I1 = BB1_Itr++, *I2 = BB2_Itr++; |
Devang Patel | 949666e | 2011-04-07 17:27:36 +0000 | [diff] [blame] | 857 | // Skip debug info if it is not identical. |
| 858 | DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1); |
| 859 | DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2); |
| 860 | if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) { |
| 861 | while (isa<DbgInfoIntrinsic>(I1)) |
| 862 | I1 = BB1_Itr++; |
| 863 | while (isa<DbgInfoIntrinsic>(I2)) |
| 864 | I2 = BB2_Itr++; |
| 865 | } |
Devang Patel | ae6c95b | 2011-04-07 00:30:15 +0000 | [diff] [blame] | 866 | if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) || |
Dale Johannesen | c1f1040 | 2009-06-15 20:59:27 +0000 | [diff] [blame] | 867 | (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))) |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 868 | return false; |
| 869 | |
| 870 | // If we get here, we can hoist at least one instruction. |
| 871 | BasicBlock *BIParent = BI->getParent(); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 872 | |
| 873 | do { |
| 874 | // If we are hoisting the terminator instruction, don't move one (making a |
| 875 | // broken BB), instead clone it, and remove BI. |
| 876 | if (isa<TerminatorInst>(I1)) |
| 877 | goto HoistTerminator; |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 878 | |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 879 | // For a normal instruction, we just move one to right before the branch, |
| 880 | // then replace all uses of the other with the first. Finally, we remove |
| 881 | // the now redundant second instruction. |
| 882 | BIParent->getInstList().splice(BI, BB1->getInstList(), I1); |
| 883 | if (!I2->use_empty()) |
| 884 | I2->replaceAllUsesWith(I1); |
Dan Gohman | 58cfa3b | 2009-08-25 22:11:20 +0000 | [diff] [blame] | 885 | I1->intersectOptionalDataWith(I2); |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 886 | I2->eraseFromParent(); |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 887 | |
Devang Patel | 65085cf | 2009-02-04 00:03:08 +0000 | [diff] [blame] | 888 | I1 = BB1_Itr++; |
Devang Patel | 65085cf | 2009-02-04 00:03:08 +0000 | [diff] [blame] | 889 | I2 = BB2_Itr++; |
Devang Patel | 949666e | 2011-04-07 17:27:36 +0000 | [diff] [blame] | 890 | // Skip debug info if it is not identical. |
| 891 | DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1); |
| 892 | DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2); |
| 893 | if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) { |
| 894 | while (isa<DbgInfoIntrinsic>(I1)) |
| 895 | I1 = BB1_Itr++; |
| 896 | while (isa<DbgInfoIntrinsic>(I2)) |
| 897 | I2 = BB2_Itr++; |
| 898 | } |
Devang Patel | ae6c95b | 2011-04-07 00:30:15 +0000 | [diff] [blame] | 899 | } while (I1->isIdenticalToWhenDefined(I2)); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 900 | |
| 901 | return true; |
| 902 | |
| 903 | HoistTerminator: |
Dale Johannesen | c1f1040 | 2009-06-15 20:59:27 +0000 | [diff] [blame] | 904 | // It may not be possible to hoist an invoke. |
| 905 | if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)) |
| 906 | return true; |
| 907 | |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 908 | // Okay, it is safe to hoist the terminator. |
Nick Lewycky | 6776064 | 2009-09-27 07:38:41 +0000 | [diff] [blame] | 909 | Instruction *NT = I1->clone(); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 910 | BIParent->getInstList().insert(BI, NT); |
Benjamin Kramer | f012705 | 2010-01-05 13:12:22 +0000 | [diff] [blame] | 911 | if (!NT->getType()->isVoidTy()) { |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 912 | I1->replaceAllUsesWith(NT); |
| 913 | I2->replaceAllUsesWith(NT); |
Chris Lattner | 86cc423 | 2007-02-11 01:37:51 +0000 | [diff] [blame] | 914 | NT->takeName(I1); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 915 | } |
| 916 | |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 917 | IRBuilder<true, NoFolder> Builder(NT); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 918 | // Hoisting one of the terminators from our successor is a great thing. |
| 919 | // Unfortunately, the successors of the if/else blocks may have PHI nodes in |
| 920 | // them. If they do, all PHI entries for BB1/BB2 must agree for all PHI |
| 921 | // nodes, so we insert select instruction to compute the final result. |
| 922 | std::map<std::pair<Value*,Value*>, SelectInst*> InsertedSelects; |
| 923 | for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) { |
| 924 | PHINode *PN; |
| 925 | for (BasicBlock::iterator BBI = SI->begin(); |
Chris Lattner | 0f535c6 | 2004-11-30 07:47:34 +0000 | [diff] [blame] | 926 | (PN = dyn_cast<PHINode>(BBI)); ++BBI) { |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 927 | Value *BB1V = PN->getIncomingValueForBlock(BB1); |
| 928 | Value *BB2V = PN->getIncomingValueForBlock(BB2); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 929 | if (BB1V == BB2V) continue; |
| 930 | |
| 931 | // These values do not agree. Insert a select instruction before NT |
| 932 | // that determines the right value. |
| 933 | SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)]; |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 934 | if (SI == 0) |
| 935 | SI = cast<SelectInst> |
| 936 | (Builder.CreateSelect(BI->getCondition(), BB1V, BB2V, |
| 937 | BB1V->getName()+"."+BB2V->getName())); |
| 938 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 939 | // Make the PHI node use the select for all incoming values for BB1/BB2 |
| 940 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) |
| 941 | if (PN->getIncomingBlock(i) == BB1 || PN->getIncomingBlock(i) == BB2) |
| 942 | PN->setIncomingValue(i, SI); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 943 | } |
| 944 | } |
| 945 | |
| 946 | // Update any PHI nodes in our new successors. |
| 947 | for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) |
| 948 | AddPredecessorToBlock(*SI, BIParent, BB1); |
Misha Brukman | fd93908 | 2005-04-21 23:48:37 +0000 | [diff] [blame] | 949 | |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 950 | EraseTerminatorInstAndDCECond(BI); |
Chris Lattner | 37dc938 | 2004-11-30 00:29:14 +0000 | [diff] [blame] | 951 | return true; |
| 952 | } |
| 953 | |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 954 | /// SpeculativelyExecuteBB - Given a conditional branch that goes to BB1 |
| 955 | /// and an BB2 and the only successor of BB1 is BB2, hoist simple code |
| 956 | /// (for now, restricted to a single instruction that's side effect free) from |
| 957 | /// the BB1 into the branch block to speculatively execute it. |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 958 | /// |
| 959 | /// Turn |
| 960 | /// BB: |
| 961 | /// %t1 = icmp |
| 962 | /// br i1 %t1, label %BB1, label %BB2 |
| 963 | /// BB1: |
| 964 | /// %t3 = add %t2, c |
| 965 | /// br label BB2 |
| 966 | /// BB2: |
| 967 | /// => |
| 968 | /// BB: |
| 969 | /// %t1 = icmp |
| 970 | /// %t4 = add %t2, c |
| 971 | /// %t3 = select i1 %t1, %t2, %t3 |
Rafael Espindola | 216dde9 | 2011-05-19 02:26:30 +0000 | [diff] [blame] | 972 | static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 973 | // Only speculatively execution a single instruction (not counting the |
| 974 | // terminator) for now. |
Devang Patel | 06b1e67 | 2009-03-06 06:00:17 +0000 | [diff] [blame] | 975 | Instruction *HInst = NULL; |
| 976 | Instruction *Term = BB1->getTerminator(); |
| 977 | for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end(); |
| 978 | BBI != BBE; ++BBI) { |
| 979 | Instruction *I = BBI; |
| 980 | // Skip debug info. |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 981 | if (isa<DbgInfoIntrinsic>(I)) continue; |
| 982 | if (I == Term) break; |
Devang Patel | 06b1e67 | 2009-03-06 06:00:17 +0000 | [diff] [blame] | 983 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 984 | if (HInst) |
Devang Patel | 06b1e67 | 2009-03-06 06:00:17 +0000 | [diff] [blame] | 985 | return false; |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 986 | HInst = I; |
Devang Patel | 06b1e67 | 2009-03-06 06:00:17 +0000 | [diff] [blame] | 987 | } |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 988 | |
| 989 | BasicBlock *BIParent = BI->getParent(); |
| 990 | |
| 991 | // Check the instruction to be hoisted, if there is one. |
| 992 | if (HInst) { |
| 993 | // Don't hoist the instruction if it's unsafe or expensive. |
| 994 | if (!isSafeToSpeculativelyExecute(HInst)) |
| 995 | return false; |
| 996 | if (ComputeSpeculationCost(HInst) > PHINodeFoldingThreshold) |
| 997 | return false; |
| 998 | |
| 999 | // Do not hoist the instruction if any of its operands are defined but not |
| 1000 | // used in this BB. The transformation will prevent the operand from |
| 1001 | // being sunk into the use block. |
| 1002 | for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end(); |
| 1003 | i != e; ++i) { |
| 1004 | Instruction *OpI = dyn_cast<Instruction>(*i); |
| 1005 | if (OpI && OpI->getParent() == BIParent && |
| 1006 | !OpI->mayHaveSideEffects() && |
| 1007 | !OpI->isUsedInBasicBlock(BIParent)) |
| 1008 | return false; |
| 1009 | } |
| 1010 | } |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1011 | |
Evan Cheng | 797d951 | 2008-06-11 19:18:20 +0000 | [diff] [blame] | 1012 | // Be conservative for now. FP select instruction can often be expensive. |
| 1013 | Value *BrCond = BI->getCondition(); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1014 | if (isa<FCmpInst>(BrCond)) |
Evan Cheng | 797d951 | 2008-06-11 19:18:20 +0000 | [diff] [blame] | 1015 | return false; |
| 1016 | |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1017 | // If BB1 is actually on the false edge of the conditional branch, remember |
| 1018 | // to swap the select operands later. |
| 1019 | bool Invert = false; |
| 1020 | if (BB1 != BI->getSuccessor(0)) { |
| 1021 | assert(BB1 == BI->getSuccessor(1) && "No edge from 'if' block?"); |
| 1022 | Invert = true; |
| 1023 | } |
| 1024 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1025 | // Collect interesting PHIs, and scan for hazards. |
| 1026 | SmallSetVector<std::pair<Value *, Value *>, 4> PHIs; |
Chris Lattner | 6fe73bb | 2009-01-19 00:36:37 +0000 | [diff] [blame] | 1027 | BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0); |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1028 | for (BasicBlock::iterator I = BB2->begin(); |
| 1029 | PHINode *PN = dyn_cast<PHINode>(I); ++I) { |
| 1030 | Value *BB1V = PN->getIncomingValueForBlock(BB1); |
| 1031 | Value *BIParentV = PN->getIncomingValueForBlock(BIParent); |
| 1032 | |
| 1033 | // Skip PHIs which are trivial. |
| 1034 | if (BB1V == BIParentV) |
| 1035 | continue; |
| 1036 | |
| 1037 | // Check for saftey. |
| 1038 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BB1V)) { |
| 1039 | // An unfolded ConstantExpr could end up getting expanded into |
| 1040 | // Instructions. Don't speculate this and another instruction at |
| 1041 | // the same time. |
| 1042 | if (HInst) |
| 1043 | return false; |
| 1044 | if (!isSafeToSpeculativelyExecute(CE)) |
| 1045 | return false; |
| 1046 | if (ComputeSpeculationCost(CE) > PHINodeFoldingThreshold) |
| 1047 | return false; |
| 1048 | } |
| 1049 | |
| 1050 | // Ok, we may insert a select for this PHI. |
| 1051 | PHIs.insert(std::make_pair(BB1V, BIParentV)); |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1052 | } |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1053 | |
| 1054 | // If there are no PHIs to process, bail early. This helps ensure idempotence |
| 1055 | // as well. |
| 1056 | if (PHIs.empty()) |
| 1057 | return false; |
Chris Lattner | 6fe73bb | 2009-01-19 00:36:37 +0000 | [diff] [blame] | 1058 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1059 | // If we get here, we can hoist the instruction and if-convert. |
| 1060 | DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *BB1 << "\n";); |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1061 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1062 | // Hoist the instruction. |
| 1063 | if (HInst) |
| 1064 | BIParent->getInstList().splice(BI, BB1->getInstList(), HInst); |
Evan Cheng | 502a4f5 | 2008-06-12 21:15:59 +0000 | [diff] [blame] | 1065 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1066 | // Insert selects and rewrite the PHI operands. |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1067 | IRBuilder<true, NoFolder> Builder(BI); |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1068 | for (unsigned i = 0, e = PHIs.size(); i != e; ++i) { |
| 1069 | Value *TrueV = PHIs[i].first; |
| 1070 | Value *FalseV = PHIs[i].second; |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1071 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 1072 | // Create a select whose true value is the speculatively executed value and |
| 1073 | // false value is the previously determined FalseV. |
| 1074 | SelectInst *SI; |
| 1075 | if (Invert) |
| 1076 | SI = cast<SelectInst> |
| 1077 | (Builder.CreateSelect(BrCond, FalseV, TrueV, |
| 1078 | FalseV->getName() + "." + TrueV->getName())); |
| 1079 | else |
| 1080 | SI = cast<SelectInst> |
| 1081 | (Builder.CreateSelect(BrCond, TrueV, FalseV, |
| 1082 | TrueV->getName() + "." + FalseV->getName())); |
| 1083 | |
| 1084 | // Make the PHI node use the select for all incoming values for "then" and |
| 1085 | // "if" blocks. |
| 1086 | for (BasicBlock::iterator I = BB2->begin(); |
| 1087 | PHINode *PN = dyn_cast<PHINode>(I); ++I) { |
| 1088 | unsigned BB1I = PN->getBasicBlockIndex(BB1); |
| 1089 | unsigned BIParentI = PN->getBasicBlockIndex(BIParent); |
| 1090 | Value *BB1V = PN->getIncomingValue(BB1I); |
| 1091 | Value *BIParentV = PN->getIncomingValue(BIParentI); |
| 1092 | if (TrueV == BB1V && FalseV == BIParentV) { |
| 1093 | PN->setIncomingValue(BB1I, SI); |
| 1094 | PN->setIncomingValue(BIParentI, SI); |
| 1095 | } |
| 1096 | } |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1097 | } |
| 1098 | |
Evan Cheng | 502a4f5 | 2008-06-12 21:15:59 +0000 | [diff] [blame] | 1099 | ++NumSpeculations; |
Evan Cheng | 4d09efd | 2008-06-07 08:52:29 +0000 | [diff] [blame] | 1100 | return true; |
| 1101 | } |
| 1102 | |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1103 | /// BlockIsSimpleEnoughToThreadThrough - Return true if we can thread a branch |
| 1104 | /// across this block. |
| 1105 | static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) { |
| 1106 | BranchInst *BI = cast<BranchInst>(BB->getTerminator()); |
Chris Lattner | e9487f0 | 2005-09-20 01:48:40 +0000 | [diff] [blame] | 1107 | unsigned Size = 0; |
| 1108 | |
Devang Patel | 9200c89 | 2009-03-10 18:00:05 +0000 | [diff] [blame] | 1109 | for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) { |
Dale Johannesen | 8483e54 | 2009-03-12 23:18:09 +0000 | [diff] [blame] | 1110 | if (isa<DbgInfoIntrinsic>(BBI)) |
| 1111 | continue; |
Chris Lattner | e9487f0 | 2005-09-20 01:48:40 +0000 | [diff] [blame] | 1112 | if (Size > 10) return false; // Don't clone large BB's. |
Dale Johannesen | 8483e54 | 2009-03-12 23:18:09 +0000 | [diff] [blame] | 1113 | ++Size; |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1114 | |
Dale Johannesen | 8483e54 | 2009-03-12 23:18:09 +0000 | [diff] [blame] | 1115 | // We can only support instructions that do not define values that are |
Chris Lattner | e9487f0 | 2005-09-20 01:48:40 +0000 | [diff] [blame] | 1116 | // live outside of the current basic block. |
| 1117 | for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end(); |
| 1118 | UI != E; ++UI) { |
| 1119 | Instruction *U = cast<Instruction>(*UI); |
| 1120 | if (U->getParent() != BB || isa<PHINode>(U)) return false; |
| 1121 | } |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1122 | |
| 1123 | // Looks ok, continue checking. |
| 1124 | } |
Chris Lattner | e9487f0 | 2005-09-20 01:48:40 +0000 | [diff] [blame] | 1125 | |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1126 | return true; |
| 1127 | } |
| 1128 | |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1129 | /// FoldCondBranchOnPHI - If we have a conditional branch on a PHI node value |
| 1130 | /// that is defined in the same block as the branch and if any PHI entries are |
| 1131 | /// constants, thread edges corresponding to that entry to be branches to their |
| 1132 | /// ultimate destination. |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 1133 | static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1134 | BasicBlock *BB = BI->getParent(); |
| 1135 | PHINode *PN = dyn_cast<PHINode>(BI->getCondition()); |
Chris Lattner | 9c88d98 | 2005-09-19 23:57:04 +0000 | [diff] [blame] | 1136 | // NOTE: we currently cannot transform this case if the PHI node is used |
| 1137 | // outside of the block. |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1138 | if (!PN || PN->getParent() != BB || !PN->hasOneUse()) |
| 1139 | return false; |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1140 | |
| 1141 | // Degenerate case of a single entry PHI. |
| 1142 | if (PN->getNumIncomingValues() == 1) { |
Chris Lattner | 29874e0 | 2008-12-03 19:44:02 +0000 | [diff] [blame] | 1143 | FoldSingleEntryPHINodes(PN->getParent()); |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1144 | return true; |
| 1145 | } |
| 1146 | |
| 1147 | // Now we know that this block has multiple preds and two succs. |
Chris Lattner | 2e42e36 | 2005-09-20 00:43:16 +0000 | [diff] [blame] | 1148 | if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false; |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1149 | |
| 1150 | // Okay, this is a simple enough basic block. See if any phi values are |
| 1151 | // constants. |
Zhou Sheng | 6b6b6ef | 2007-01-11 12:24:14 +0000 | [diff] [blame] | 1152 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1153 | ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i)); |
| 1154 | if (CB == 0 || !CB->getType()->isIntegerTy(1)) continue; |
| 1155 | |
| 1156 | // Okay, we now know that all edges from PredBB should be revectored to |
| 1157 | // branch to RealDest. |
| 1158 | BasicBlock *PredBB = PN->getIncomingBlock(i); |
| 1159 | BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue()); |
| 1160 | |
| 1161 | if (RealDest == BB) continue; // Skip self loops. |
Bill Wendling | 6a648b8 | 2011-06-04 09:42:04 +0000 | [diff] [blame] | 1162 | // Skip if the predecessor's terminator is an indirect branch. |
| 1163 | if (isa<IndirectBrInst>(PredBB->getTerminator())) continue; |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1164 | |
| 1165 | // The dest block might have PHI nodes, other predecessors and other |
| 1166 | // difficult cases. Instead of being smart about this, just insert a new |
| 1167 | // block that jumps to the destination block, effectively splitting |
| 1168 | // the edge we are about to create. |
| 1169 | BasicBlock *EdgeBB = BasicBlock::Create(BB->getContext(), |
| 1170 | RealDest->getName()+".critedge", |
| 1171 | RealDest->getParent(), RealDest); |
| 1172 | BranchInst::Create(RealDest, EdgeBB); |
Chris Lattner | 6de0a28 | 2010-12-14 07:09:42 +0000 | [diff] [blame] | 1173 | |
| 1174 | // Update PHI nodes. |
| 1175 | AddPredecessorToBlock(RealDest, EdgeBB, BB); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1176 | |
| 1177 | // BB may have instructions that are being threaded over. Clone these |
| 1178 | // instructions into EdgeBB. We know that there will be no uses of the |
| 1179 | // cloned instructions outside of EdgeBB. |
| 1180 | BasicBlock::iterator InsertPt = EdgeBB->begin(); |
| 1181 | DenseMap<Value*, Value*> TranslateMap; // Track translated values. |
| 1182 | for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) { |
| 1183 | if (PHINode *PN = dyn_cast<PHINode>(BBI)) { |
| 1184 | TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB); |
| 1185 | continue; |
| 1186 | } |
| 1187 | // Clone the instruction. |
| 1188 | Instruction *N = BBI->clone(); |
| 1189 | if (BBI->hasName()) N->setName(BBI->getName()+".c"); |
| 1190 | |
| 1191 | // Update operands due to translation. |
| 1192 | for (User::op_iterator i = N->op_begin(), e = N->op_end(); |
| 1193 | i != e; ++i) { |
| 1194 | DenseMap<Value*, Value*>::iterator PI = TranslateMap.find(*i); |
| 1195 | if (PI != TranslateMap.end()) |
| 1196 | *i = PI->second; |
| 1197 | } |
| 1198 | |
| 1199 | // Check for trivial simplification. |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 1200 | if (Value *V = SimplifyInstruction(N, TD)) { |
| 1201 | TranslateMap[BBI] = V; |
| 1202 | delete N; // Instruction folded away, don't need actual inst |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1203 | } else { |
| 1204 | // Insert the new instruction into its new home. |
| 1205 | EdgeBB->getInstList().insert(InsertPt, N); |
| 1206 | if (!BBI->use_empty()) |
| 1207 | TranslateMap[BBI] = N; |
| 1208 | } |
| 1209 | } |
| 1210 | |
| 1211 | // Loop over all of the edges from PredBB to BB, changing them to branch |
| 1212 | // to EdgeBB instead. |
| 1213 | TerminatorInst *PredBBTI = PredBB->getTerminator(); |
| 1214 | for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i) |
| 1215 | if (PredBBTI->getSuccessor(i) == BB) { |
| 1216 | BB->removePredecessor(PredBB); |
| 1217 | PredBBTI->setSuccessor(i, EdgeBB); |
| 1218 | } |
Bill Wendling | 6a648b8 | 2011-06-04 09:42:04 +0000 | [diff] [blame] | 1219 | |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1220 | // Recurse, simplifying any other constants. |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 1221 | return FoldCondBranchOnPHI(BI, TD) | true; |
Zhou Sheng | 6b6b6ef | 2007-01-11 12:24:14 +0000 | [diff] [blame] | 1222 | } |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1223 | |
| 1224 | return false; |
| 1225 | } |
| 1226 | |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1227 | /// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry |
| 1228 | /// PHI node, see if we can eliminate it. |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1229 | static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1230 | // Ok, this is a two entry PHI node. Check to see if this is a simple "if |
| 1231 | // statement", which has a very simple dominance structure. Basically, we |
| 1232 | // are trying to find the condition that is being branched on, which |
| 1233 | // subsequently causes this merge to happen. We really want control |
| 1234 | // dependence information for this check, but simplifycfg can't keep it up |
| 1235 | // to date, and this catches most of the cases we care about anyway. |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1236 | BasicBlock *BB = PN->getParent(); |
| 1237 | BasicBlock *IfTrue, *IfFalse; |
| 1238 | Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse); |
Chris Lattner | 60d410d | 2010-12-14 08:01:53 +0000 | [diff] [blame] | 1239 | if (!IfCond || |
| 1240 | // Don't bother if the branch will be constant folded trivially. |
| 1241 | isa<ConstantInt>(IfCond)) |
| 1242 | return false; |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1243 | |
Chris Lattner | 822a879 | 2006-11-18 19:19:36 +0000 | [diff] [blame] | 1244 | // Okay, we found that we can merge this two-entry phi node into a select. |
| 1245 | // Doing so would require us to fold *all* two entry phi nodes in this block. |
| 1246 | // At some point this becomes non-profitable (particularly if the target |
| 1247 | // doesn't support cmov's). Only do this transformation if there are two or |
| 1248 | // fewer PHI nodes in this block. |
| 1249 | unsigned NumPhis = 0; |
| 1250 | for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I) |
| 1251 | if (NumPhis > 2) |
| 1252 | return false; |
| 1253 | |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1254 | // Loop over the PHI's seeing if we can promote them all to select |
| 1255 | // instructions. While we are at it, keep track of the instructions |
| 1256 | // that need to be moved to the dominating block. |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 1257 | SmallPtrSet<Instruction*, 4> AggressiveInsts; |
Peter Collingbourne | 57808b3 | 2011-04-29 18:47:38 +0000 | [diff] [blame] | 1258 | unsigned MaxCostVal0 = PHINodeFoldingThreshold, |
| 1259 | MaxCostVal1 = PHINodeFoldingThreshold; |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1260 | |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1261 | for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) { |
| 1262 | PHINode *PN = cast<PHINode>(II++); |
Chris Lattner | 07ff353 | 2010-12-14 07:20:29 +0000 | [diff] [blame] | 1263 | if (Value *V = SimplifyInstruction(PN, TD)) { |
| 1264 | PN->replaceAllUsesWith(V); |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1265 | PN->eraseFromParent(); |
Chris Lattner | 07ff353 | 2010-12-14 07:20:29 +0000 | [diff] [blame] | 1266 | continue; |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1267 | } |
Chris Lattner | 07ff353 | 2010-12-14 07:20:29 +0000 | [diff] [blame] | 1268 | |
Peter Collingbourne | f15907f | 2011-04-29 18:47:31 +0000 | [diff] [blame] | 1269 | if (!DominatesMergePoint(PN->getIncomingValue(0), BB, &AggressiveInsts, |
| 1270 | MaxCostVal0) || |
| 1271 | !DominatesMergePoint(PN->getIncomingValue(1), BB, &AggressiveInsts, |
| 1272 | MaxCostVal1)) |
Chris Lattner | 07ff353 | 2010-12-14 07:20:29 +0000 | [diff] [blame] | 1273 | return false; |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1274 | } |
| 1275 | |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 1276 | // If we folded the the first phi, PN dangles at this point. Refresh it. If |
| 1277 | // we ran out of PHIs then we simplified them all. |
| 1278 | PN = dyn_cast<PHINode>(BB->begin()); |
| 1279 | if (PN == 0) return true; |
| 1280 | |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1281 | // Don't fold i1 branches on PHIs which contain binary operators. These can |
| 1282 | // often be turned into switches and other things. |
| 1283 | if (PN->getType()->isIntegerTy(1) && |
| 1284 | (isa<BinaryOperator>(PN->getIncomingValue(0)) || |
| 1285 | isa<BinaryOperator>(PN->getIncomingValue(1)) || |
| 1286 | isa<BinaryOperator>(IfCond))) |
| 1287 | return false; |
| 1288 | |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1289 | // If we all PHI nodes are promotable, check to make sure that all |
| 1290 | // instructions in the predecessor blocks can be promoted as well. If |
| 1291 | // not, we won't be able to get rid of the control flow, so it's not |
| 1292 | // worth promoting to select instructions. |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 1293 | BasicBlock *DomBlock = 0; |
| 1294 | BasicBlock *IfBlock1 = PN->getIncomingBlock(0); |
| 1295 | BasicBlock *IfBlock2 = PN->getIncomingBlock(1); |
| 1296 | if (cast<BranchInst>(IfBlock1->getTerminator())->isConditional()) { |
| 1297 | IfBlock1 = 0; |
| 1298 | } else { |
| 1299 | DomBlock = *pred_begin(IfBlock1); |
| 1300 | for (BasicBlock::iterator I = IfBlock1->begin();!isa<TerminatorInst>(I);++I) |
Devang Patel | 383d7ed | 2009-02-03 22:12:02 +0000 | [diff] [blame] | 1301 | if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) { |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1302 | // This is not an aggressive instruction that we can promote. |
| 1303 | // Because of this, we won't be able to get rid of the control |
| 1304 | // flow, so the xform is not worth it. |
| 1305 | return false; |
| 1306 | } |
| 1307 | } |
| 1308 | |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 1309 | if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) { |
| 1310 | IfBlock2 = 0; |
| 1311 | } else { |
| 1312 | DomBlock = *pred_begin(IfBlock2); |
| 1313 | for (BasicBlock::iterator I = IfBlock2->begin();!isa<TerminatorInst>(I);++I) |
Devang Patel | 383d7ed | 2009-02-03 22:12:02 +0000 | [diff] [blame] | 1314 | if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) { |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1315 | // This is not an aggressive instruction that we can promote. |
| 1316 | // Because of this, we won't be able to get rid of the control |
| 1317 | // flow, so the xform is not worth it. |
| 1318 | return false; |
| 1319 | } |
| 1320 | } |
Chris Lattner | e0b18e5 | 2010-12-14 07:23:10 +0000 | [diff] [blame] | 1321 | |
| 1322 | DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: " |
Chris Lattner | 44da7ca | 2010-12-14 07:41:39 +0000 | [diff] [blame] | 1323 | << IfTrue->getName() << " F: " << IfFalse->getName() << "\n"); |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1324 | |
| 1325 | // If we can still promote the PHI nodes after this gauntlet of tests, |
| 1326 | // do all of the PHI's now. |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1327 | Instruction *InsertPt = DomBlock->getTerminator(); |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1328 | IRBuilder<true, NoFolder> Builder(InsertPt); |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1329 | |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1330 | // Move all 'aggressive' instructions, which are defined in the |
| 1331 | // conditional parts of the if's up to the dominating block. |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1332 | if (IfBlock1) |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1333 | DomBlock->getInstList().splice(InsertPt, |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1334 | IfBlock1->getInstList(), IfBlock1->begin(), |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1335 | IfBlock1->getTerminator()); |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1336 | if (IfBlock2) |
Chris Lattner | 3aff13b | 2010-12-14 08:46:09 +0000 | [diff] [blame] | 1337 | DomBlock->getInstList().splice(InsertPt, |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1338 | IfBlock2->getInstList(), IfBlock2->begin(), |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1339 | IfBlock2->getTerminator()); |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1340 | |
| 1341 | while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) { |
| 1342 | // Change the PHI node into a select instruction. |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1343 | Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse); |
| 1344 | Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue); |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1345 | |
Devang Patel | f60364d | 2011-05-18 18:16:44 +0000 | [diff] [blame] | 1346 | SelectInst *NV = |
| 1347 | cast<SelectInst>(Builder.CreateSelect(IfCond, TrueVal, FalseVal, "")); |
Chris Lattner | 86cc423 | 2007-02-11 01:37:51 +0000 | [diff] [blame] | 1348 | PN->replaceAllUsesWith(NV); |
| 1349 | NV->takeName(PN); |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 1350 | PN->eraseFromParent(); |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1351 | } |
Chris Lattner | 60d410d | 2010-12-14 08:01:53 +0000 | [diff] [blame] | 1352 | |
| 1353 | // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement |
| 1354 | // has been flattened. Change DomBlock to jump directly to our new block to |
| 1355 | // avoid other simplifycfg's kicking in on the diamond. |
| 1356 | TerminatorInst *OldTI = DomBlock->getTerminator(); |
Devang Patel | f60364d | 2011-05-18 18:16:44 +0000 | [diff] [blame] | 1357 | Builder.SetInsertPoint(OldTI); |
| 1358 | Builder.CreateBr(BB); |
Chris Lattner | 60d410d | 2010-12-14 08:01:53 +0000 | [diff] [blame] | 1359 | OldTI->eraseFromParent(); |
Chris Lattner | f58c1a5 | 2005-09-23 06:39:30 +0000 | [diff] [blame] | 1360 | return true; |
| 1361 | } |
Chris Lattner | eaba3a1 | 2005-09-19 23:49:37 +0000 | [diff] [blame] | 1362 | |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1363 | /// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes |
| 1364 | /// to two returning blocks, try to merge them together into one return, |
| 1365 | /// introducing a select if the return values disagree. |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 1366 | static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, |
| 1367 | IRBuilder<> &Builder) { |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1368 | assert(BI->isConditional() && "Must be a conditional branch"); |
| 1369 | BasicBlock *TrueSucc = BI->getSuccessor(0); |
| 1370 | BasicBlock *FalseSucc = BI->getSuccessor(1); |
| 1371 | ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator()); |
| 1372 | ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator()); |
| 1373 | |
| 1374 | // Check to ensure both blocks are empty (just a return) or optionally empty |
| 1375 | // with PHI nodes. If there are other instructions, merging would cause extra |
| 1376 | // computation on one path or the other. |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1377 | if (!TrueSucc->getFirstNonPHIOrDbg()->isTerminator()) |
Devang Patel | 2cc86a1 | 2009-02-05 00:30:42 +0000 | [diff] [blame] | 1378 | return false; |
Chris Lattner | 9a2b72a | 2010-12-13 01:47:07 +0000 | [diff] [blame] | 1379 | if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator()) |
Devang Patel | 2cc86a1 | 2009-02-05 00:30:42 +0000 | [diff] [blame] | 1380 | return false; |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1381 | |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 1382 | Builder.SetInsertPoint(BI); |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1383 | // Okay, we found a branch that is going to two return nodes. If |
| 1384 | // there is no return value for this function, just change the |
| 1385 | // branch into a return. |
| 1386 | if (FalseRet->getNumOperands() == 0) { |
| 1387 | TrueSucc->removePredecessor(BI->getParent()); |
| 1388 | FalseSucc->removePredecessor(BI->getParent()); |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 1389 | Builder.CreateRetVoid(); |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 1390 | EraseTerminatorInstAndDCECond(BI); |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1391 | return true; |
| 1392 | } |
| 1393 | |
Dan Gohman | fc74abf | 2008-07-23 00:34:11 +0000 | [diff] [blame] | 1394 | // Otherwise, figure out what the true and false return values are |
| 1395 | // so we can insert a new select instruction. |
| 1396 | Value *TrueValue = TrueRet->getReturnValue(); |
| 1397 | Value *FalseValue = FalseRet->getReturnValue(); |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1398 | |
Dan Gohman | fc74abf | 2008-07-23 00:34:11 +0000 | [diff] [blame] | 1399 | // Unwrap any PHI nodes in the return blocks. |
| 1400 | if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue)) |
| 1401 | if (TVPN->getParent() == TrueSucc) |
| 1402 | TrueValue = TVPN->getIncomingValueForBlock(BI->getParent()); |
| 1403 | if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue)) |
| 1404 | if (FVPN->getParent() == FalseSucc) |
| 1405 | FalseValue = FVPN->getIncomingValueForBlock(BI->getParent()); |
| 1406 | |
| 1407 | // In order for this transformation to be safe, we must be able to |
| 1408 | // unconditionally execute both operands to the return. This is |
| 1409 | // normally the case, but we could have a potentially-trapping |
| 1410 | // constant expression that prevents this transformation from being |
| 1411 | // safe. |
| 1412 | if (ConstantExpr *TCV = dyn_cast_or_null<ConstantExpr>(TrueValue)) |
| 1413 | if (TCV->canTrap()) |
| 1414 | return false; |
| 1415 | if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue)) |
| 1416 | if (FCV->canTrap()) |
| 1417 | return false; |
| 1418 | |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1419 | // Okay, we collected all the mapped values and checked them for sanity, and |
| 1420 | // defined to really do this transformation. First, update the CFG. |
| 1421 | TrueSucc->removePredecessor(BI->getParent()); |
| 1422 | FalseSucc->removePredecessor(BI->getParent()); |
| 1423 | |
| 1424 | // Insert select instructions where needed. |
| 1425 | Value *BrCond = BI->getCondition(); |
Dan Gohman | fc74abf | 2008-07-23 00:34:11 +0000 | [diff] [blame] | 1426 | if (TrueValue) { |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1427 | // Insert a select if the results differ. |
Dan Gohman | fc74abf | 2008-07-23 00:34:11 +0000 | [diff] [blame] | 1428 | if (TrueValue == FalseValue || isa<UndefValue>(FalseValue)) { |
| 1429 | } else if (isa<UndefValue>(TrueValue)) { |
| 1430 | TrueValue = FalseValue; |
| 1431 | } else { |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 1432 | TrueValue = Builder.CreateSelect(BrCond, TrueValue, |
| 1433 | FalseValue, "retval"); |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1434 | } |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1435 | } |
| 1436 | |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 1437 | Value *RI = !TrueValue ? |
| 1438 | Builder.CreateRetVoid() : Builder.CreateRet(TrueValue); |
| 1439 | |
Daniel Dunbar | e317bcc | 2009-08-23 10:29:55 +0000 | [diff] [blame] | 1440 | (void) RI; |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1441 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 1442 | DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:" |
Chris Lattner | bdff548 | 2009-08-23 04:37:46 +0000 | [diff] [blame] | 1443 | << "\n " << *BI << "NewRet = " << *RI |
| 1444 | << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc); |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1445 | |
Eli Friedman | 080efb8 | 2008-12-16 20:54:32 +0000 | [diff] [blame] | 1446 | EraseTerminatorInstAndDCECond(BI); |
| 1447 | |
Chris Lattner | c9e495c | 2008-04-24 00:01:19 +0000 | [diff] [blame] | 1448 | return true; |
| 1449 | } |
| 1450 | |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1451 | /// ExtractBranchMetadata - Given a conditional BranchInstruction, retrieve the |
| 1452 | /// probabilities of the branch taking each edge. Fills in the two APInt |
| 1453 | /// parameters and return true, or returns false if no or invalid metadata was |
| 1454 | /// found. |
| 1455 | static bool ExtractBranchMetadata(BranchInst *BI, |
| 1456 | APInt &ProbTrue, APInt &ProbFalse) { |
| 1457 | assert(BI->isConditional() && |
| 1458 | "Looking for probabilities on unconditional branch?"); |
| 1459 | MDNode *ProfileData = BI->getMetadata(LLVMContext::MD_prof); |
Nick Lewycky | 9196848 | 2011-12-27 18:27:22 +0000 | [diff] [blame] | 1460 | if (!ProfileData || ProfileData->getNumOperands() != 3) return false; |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1461 | ConstantInt *CITrue = dyn_cast<ConstantInt>(ProfileData->getOperand(1)); |
| 1462 | ConstantInt *CIFalse = dyn_cast<ConstantInt>(ProfileData->getOperand(2)); |
Nick Lewycky | 9196848 | 2011-12-27 18:27:22 +0000 | [diff] [blame] | 1463 | if (!CITrue || !CIFalse) return false; |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1464 | ProbTrue = CITrue->getValue(); |
| 1465 | ProbFalse = CIFalse->getValue(); |
| 1466 | assert(ProbTrue.getBitWidth() == 32 && ProbFalse.getBitWidth() == 32 && |
| 1467 | "Branch probability metadata must be 32-bit integers"); |
| 1468 | return true; |
| 1469 | } |
| 1470 | |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1471 | /// MultiplyAndLosePrecision - Multiplies A and B, then returns the result. In |
| 1472 | /// the event of overflow, logically-shifts all four inputs right until the |
| 1473 | /// multiply fits. |
| 1474 | static APInt MultiplyAndLosePrecision(APInt &A, APInt &B, APInt &C, APInt &D, |
| 1475 | unsigned &BitsLost) { |
| 1476 | BitsLost = 0; |
| 1477 | bool Overflow = false; |
| 1478 | APInt Result = A.umul_ov(B, Overflow); |
| 1479 | if (Overflow) { |
| 1480 | APInt MaxB = APInt::getMaxValue(A.getBitWidth()).udiv(A); |
| 1481 | do { |
| 1482 | B = B.lshr(1); |
| 1483 | ++BitsLost; |
| 1484 | } while (B.ugt(MaxB)); |
| 1485 | A = A.lshr(BitsLost); |
| 1486 | C = C.lshr(BitsLost); |
| 1487 | D = D.lshr(BitsLost); |
| 1488 | Result = A * B; |
| 1489 | } |
| 1490 | return Result; |
| 1491 | } |
| 1492 | |
| 1493 | |
Chris Lattner | c8fbc34 | 2011-04-11 23:24:57 +0000 | [diff] [blame] | 1494 | /// FoldBranchToCommonDest - If this basic block is simple enough, and if a |
| 1495 | /// predecessor branches to us and one of our successors, fold the block into |
| 1496 | /// the predecessor and use logical operations to pick the right destination. |
Dan Gohman | 4b35f83 | 2009-06-27 21:30:38 +0000 | [diff] [blame] | 1497 | bool llvm::FoldBranchToCommonDest(BranchInst *BI) { |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 1498 | BasicBlock *BB = BI->getParent(); |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1499 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1500 | Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()); |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1501 | if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) || |
| 1502 | Cond->getParent() != BB || !Cond->hasOneUse()) |
| 1503 | return false; |
Devang Patel | d418194 | 2011-04-06 22:37:20 +0000 | [diff] [blame] | 1504 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1505 | // Only allow this if the condition is a simple instruction that can be |
| 1506 | // executed unconditionally. It must be in the same block as the branch, and |
| 1507 | // must be at the front of the block. |
Devang Patel | d0a203d | 2009-02-04 21:39:48 +0000 | [diff] [blame] | 1508 | BasicBlock::iterator FrontIt = BB->front(); |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1509 | |
Devang Patel | d0a203d | 2009-02-04 21:39:48 +0000 | [diff] [blame] | 1510 | // Ignore dbg intrinsics. |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1511 | while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt; |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 1512 | |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1513 | // Allow a single instruction to be hoisted in addition to the compare |
| 1514 | // that feeds the branch. We later ensure that any values that _it_ uses |
| 1515 | // were also live in the predecessor, so that we don't unnecessarily create |
| 1516 | // register pressure or inhibit out-of-order execution. |
| 1517 | Instruction *BonusInst = 0; |
| 1518 | if (&*FrontIt != Cond && |
Owen Anderson | 2722dfa | 2010-07-15 16:38:22 +0000 | [diff] [blame] | 1519 | FrontIt->hasOneUse() && *FrontIt->use_begin() == Cond && |
Dan Gohman | f042660 | 2011-12-14 23:49:11 +0000 | [diff] [blame] | 1520 | isSafeToSpeculativelyExecute(FrontIt)) { |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1521 | BonusInst = &*FrontIt; |
| 1522 | ++FrontIt; |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1523 | |
| 1524 | // Ignore dbg intrinsics. |
| 1525 | while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt; |
Devang Patel | 60d490c | 2011-04-07 23:11:25 +0000 | [diff] [blame] | 1526 | } |
| 1527 | |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1528 | // Only a single bonus inst is allowed. |
| 1529 | if (&*FrontIt != Cond) |
| 1530 | return false; |
| 1531 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1532 | // Make sure the instruction after the condition is the cond branch. |
| 1533 | BasicBlock::iterator CondIt = Cond; ++CondIt; |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1534 | |
Devang Patel | d0a203d | 2009-02-04 21:39:48 +0000 | [diff] [blame] | 1535 | // Ingore dbg intrinsics. |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1536 | while (isa<DbgInfoIntrinsic>(CondIt)) ++CondIt; |
| 1537 | |
| 1538 | if (&*CondIt != BI) |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1539 | return false; |
Chris Lattner | 6ff645b | 2009-01-19 23:03:13 +0000 | [diff] [blame] | 1540 | |
| 1541 | // Cond is known to be a compare or binary operator. Check to make sure that |
| 1542 | // neither operand is a potentially-trapping constant expression. |
| 1543 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(0))) |
| 1544 | if (CE->canTrap()) |
| 1545 | return false; |
| 1546 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1))) |
| 1547 | if (CE->canTrap()) |
| 1548 | return false; |
| 1549 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1550 | // Finally, don't infinitely unroll conditional loops. |
| 1551 | BasicBlock *TrueDest = BI->getSuccessor(0); |
| 1552 | BasicBlock *FalseDest = BI->getSuccessor(1); |
| 1553 | if (TrueDest == BB || FalseDest == BB) |
| 1554 | return false; |
Devang Patel | d418194 | 2011-04-06 22:37:20 +0000 | [diff] [blame] | 1555 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1556 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { |
| 1557 | BasicBlock *PredBlock = *PI; |
| 1558 | BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator()); |
Chris Lattner | 6ff645b | 2009-01-19 23:03:13 +0000 | [diff] [blame] | 1559 | |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 1560 | // Check that we have two conditional branches. If there is a PHI node in |
| 1561 | // the common successor, verify that the same value flows in from both |
| 1562 | // blocks. |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1563 | if (PBI == 0 || PBI->isUnconditional() || !SafeToMergeTerminators(BI, PBI)) |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1564 | continue; |
| 1565 | |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1566 | // Determine if the two branches share a common destination. |
| 1567 | Instruction::BinaryOps Opc; |
| 1568 | bool InvertPredCond = false; |
| 1569 | |
| 1570 | if (PBI->getSuccessor(0) == TrueDest) |
| 1571 | Opc = Instruction::Or; |
| 1572 | else if (PBI->getSuccessor(1) == FalseDest) |
| 1573 | Opc = Instruction::And; |
| 1574 | else if (PBI->getSuccessor(0) == FalseDest) |
| 1575 | Opc = Instruction::And, InvertPredCond = true; |
| 1576 | else if (PBI->getSuccessor(1) == TrueDest) |
| 1577 | Opc = Instruction::Or, InvertPredCond = true; |
| 1578 | else |
| 1579 | continue; |
| 1580 | |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1581 | // Ensure that any values used in the bonus instruction are also used |
| 1582 | // by the terminator of the predecessor. This means that those values |
| 1583 | // must already have been resolved, so we won't be inhibiting the |
| 1584 | // out-of-order core by speculating them earlier. |
| 1585 | if (BonusInst) { |
| 1586 | // Collect the values used by the bonus inst |
| 1587 | SmallPtrSet<Value*, 4> UsedValues; |
| 1588 | for (Instruction::op_iterator OI = BonusInst->op_begin(), |
| 1589 | OE = BonusInst->op_end(); OI != OE; ++OI) { |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 1590 | Value *V = *OI; |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1591 | if (!isa<Constant>(V)) |
| 1592 | UsedValues.insert(V); |
| 1593 | } |
| 1594 | |
| 1595 | SmallVector<std::pair<Value*, unsigned>, 4> Worklist; |
| 1596 | Worklist.push_back(std::make_pair(PBI->getOperand(0), 0)); |
| 1597 | |
| 1598 | // Walk up to four levels back up the use-def chain of the predecessor's |
| 1599 | // terminator to see if all those values were used. The choice of four |
| 1600 | // levels is arbitrary, to provide a compile-time-cost bound. |
| 1601 | while (!Worklist.empty()) { |
| 1602 | std::pair<Value*, unsigned> Pair = Worklist.back(); |
| 1603 | Worklist.pop_back(); |
| 1604 | |
| 1605 | if (Pair.second >= 4) continue; |
| 1606 | UsedValues.erase(Pair.first); |
| 1607 | if (UsedValues.empty()) break; |
| 1608 | |
Chris Lattner | daa02ab | 2010-12-13 07:00:06 +0000 | [diff] [blame] | 1609 | if (Instruction *I = dyn_cast<Instruction>(Pair.first)) { |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1610 | for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); |
| 1611 | OI != OE; ++OI) |
| 1612 | Worklist.push_back(std::make_pair(OI->get(), Pair.second+1)); |
| 1613 | } |
| 1614 | } |
| 1615 | |
| 1616 | if (!UsedValues.empty()) return false; |
| 1617 | } |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1618 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 1619 | DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB); |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1620 | IRBuilder<> Builder(PBI); |
| 1621 | |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1622 | // If we need to invert the condition in the pred block to match, do so now. |
| 1623 | if (InvertPredCond) { |
Chris Lattner | daa02ab | 2010-12-13 07:00:06 +0000 | [diff] [blame] | 1624 | Value *NewCond = PBI->getCondition(); |
| 1625 | |
| 1626 | if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) { |
| 1627 | CmpInst *CI = cast<CmpInst>(NewCond); |
| 1628 | CI->setPredicate(CI->getInversePredicate()); |
| 1629 | } else { |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1630 | NewCond = Builder.CreateNot(NewCond, |
| 1631 | PBI->getCondition()->getName()+".not"); |
Chris Lattner | daa02ab | 2010-12-13 07:00:06 +0000 | [diff] [blame] | 1632 | } |
| 1633 | |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1634 | PBI->setCondition(NewCond); |
Nick Lewycky | c9a1aed | 2011-12-26 20:54:14 +0000 | [diff] [blame] | 1635 | PBI->swapSuccessors(); |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1636 | } |
Chris Lattner | 70087f3 | 2008-07-13 21:15:11 +0000 | [diff] [blame] | 1637 | |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1638 | // If we have a bonus inst, clone it into the predecessor block. |
| 1639 | Instruction *NewBonus = 0; |
| 1640 | if (BonusInst) { |
| 1641 | NewBonus = BonusInst->clone(); |
| 1642 | PredBlock->getInstList().insert(PBI, NewBonus); |
| 1643 | NewBonus->takeName(BonusInst); |
| 1644 | BonusInst->setName(BonusInst->getName()+".old"); |
| 1645 | } |
| 1646 | |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1647 | // Clone Cond into the predecessor basic block, and or/and the |
| 1648 | // two conditions together. |
Nick Lewycky | 6776064 | 2009-09-27 07:38:41 +0000 | [diff] [blame] | 1649 | Instruction *New = Cond->clone(); |
Owen Anderson | e84178a | 2010-07-14 19:52:16 +0000 | [diff] [blame] | 1650 | if (BonusInst) New->replaceUsesOfWith(BonusInst, NewBonus); |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1651 | PredBlock->getInstList().insert(PBI, New); |
| 1652 | New->takeName(Cond); |
| 1653 | Cond->setName(New->getName()+".old"); |
Chris Lattner | 70087f3 | 2008-07-13 21:15:11 +0000 | [diff] [blame] | 1654 | |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1655 | Instruction *NewCond = |
| 1656 | cast<Instruction>(Builder.CreateBinOp(Opc, PBI->getCondition(), |
| 1657 | New, "or.cond")); |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1658 | PBI->setCondition(NewCond); |
| 1659 | if (PBI->getSuccessor(0) == BB) { |
| 1660 | AddPredecessorToBlock(TrueDest, PredBlock, BB); |
| 1661 | PBI->setSuccessor(0, TrueDest); |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1662 | } |
Chris Lattner | 3698909 | 2008-07-13 21:20:19 +0000 | [diff] [blame] | 1663 | if (PBI->getSuccessor(1) == BB) { |
| 1664 | AddPredecessorToBlock(FalseDest, PredBlock, BB); |
| 1665 | PBI->setSuccessor(1, FalseDest); |
| 1666 | } |
Devang Patel | d418194 | 2011-04-06 22:37:20 +0000 | [diff] [blame] | 1667 | |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1668 | // TODO: If BB is reachable from all paths through PredBlock, then we |
| 1669 | // could replace PBI's branch probabilities with BI's. |
| 1670 | |
| 1671 | // Merge probability data into PredBlock's branch. |
| 1672 | APInt A, B, C, D; |
| 1673 | if (ExtractBranchMetadata(PBI, C, D) && ExtractBranchMetadata(BI, A, B)) { |
Nick Lewycky | 8da7ddf | 2011-12-28 06:57:32 +0000 | [diff] [blame] | 1674 | // Given IR which does: |
| 1675 | // bbA: |
| 1676 | // br i1 %x, label %bbB, label %bbC |
| 1677 | // bbB: |
| 1678 | // br i1 %y, label %bbD, label %bbC |
| 1679 | // Let's call the probability that we take the edge from %bbA to %bbB |
| 1680 | // 'a', from %bbA to %bbC, 'b', from %bbB to %bbD 'c' and from %bbB to |
| 1681 | // %bbC probability 'd'. |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1682 | // |
Nick Lewycky | 8da7ddf | 2011-12-28 06:57:32 +0000 | [diff] [blame] | 1683 | // We transform the IR into: |
| 1684 | // bbA: |
| 1685 | // br i1 %z, label %bbD, label %bbC |
| 1686 | // where the probability of going to %bbD is (a*c) and going to bbC is |
| 1687 | // (b+a*d). |
| 1688 | // |
| 1689 | // Probabilities aren't stored as ratios directly. Using branch weights, |
| 1690 | // we get: |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1691 | // (a*c)% = A*C, (b+(a*d))% = A*D+B*C+B*D. |
| 1692 | |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1693 | // In the event of overflow, we want to drop the LSB of the input |
| 1694 | // probabilities. |
| 1695 | unsigned BitsLost; |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1696 | |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1697 | // Ignore overflow result on ProbTrue. |
| 1698 | APInt ProbTrue = MultiplyAndLosePrecision(A, C, B, D, BitsLost); |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1699 | |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1700 | APInt Tmp1 = MultiplyAndLosePrecision(B, D, A, C, BitsLost); |
| 1701 | if (BitsLost) { |
| 1702 | ProbTrue = ProbTrue.lshr(BitsLost*2); |
| 1703 | } |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1704 | |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1705 | APInt Tmp2 = MultiplyAndLosePrecision(A, D, C, B, BitsLost); |
| 1706 | if (BitsLost) { |
| 1707 | ProbTrue = ProbTrue.lshr(BitsLost*2); |
| 1708 | Tmp1 = Tmp1.lshr(BitsLost*2); |
| 1709 | } |
| 1710 | |
| 1711 | APInt Tmp3 = MultiplyAndLosePrecision(B, C, A, D, BitsLost); |
| 1712 | if (BitsLost) { |
| 1713 | ProbTrue = ProbTrue.lshr(BitsLost*2); |
| 1714 | Tmp1 = Tmp1.lshr(BitsLost*2); |
| 1715 | Tmp2 = Tmp2.lshr(BitsLost*2); |
| 1716 | } |
| 1717 | |
| 1718 | bool Overflow1 = false, Overflow2 = false; |
| 1719 | APInt Tmp4 = Tmp2.uadd_ov(Tmp3, Overflow1); |
| 1720 | APInt ProbFalse = Tmp4.uadd_ov(Tmp1, Overflow2); |
| 1721 | |
| 1722 | if (Overflow1 || Overflow2) { |
| 1723 | ProbTrue = ProbTrue.lshr(1); |
| 1724 | Tmp1 = Tmp1.lshr(1); |
| 1725 | Tmp2 = Tmp2.lshr(1); |
| 1726 | Tmp3 = Tmp3.lshr(1); |
| 1727 | Tmp4 = Tmp2 + Tmp3; |
| 1728 | ProbFalse = Tmp4 + Tmp1; |
| 1729 | } |
| 1730 | |
| 1731 | // The sum of branch weights must fit in 32-bits. |
| 1732 | if (ProbTrue.isNegative() && ProbFalse.isNegative()) { |
| 1733 | ProbTrue = ProbTrue.lshr(1); |
| 1734 | ProbFalse = ProbFalse.lshr(1); |
| 1735 | } |
| 1736 | |
| 1737 | if (ProbTrue != ProbFalse) { |
| 1738 | // Normalize the result. |
| 1739 | APInt GCD = APIntOps::GreatestCommonDivisor(ProbTrue, ProbFalse); |
| 1740 | ProbTrue = ProbTrue.udiv(GCD); |
| 1741 | ProbFalse = ProbFalse.udiv(GCD); |
| 1742 | |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1743 | LLVMContext &Context = BI->getContext(); |
| 1744 | Value *Ops[3]; |
| 1745 | Ops[0] = BI->getMetadata(LLVMContext::MD_prof)->getOperand(0); |
| 1746 | Ops[1] = ConstantInt::get(Context, ProbTrue); |
| 1747 | Ops[2] = ConstantInt::get(Context, ProbFalse); |
| 1748 | PBI->setMetadata(LLVMContext::MD_prof, MDNode::get(Context, Ops)); |
Nick Lewycky | 6c00c6a | 2012-01-25 09:43:14 +0000 | [diff] [blame] | 1749 | } else { |
| 1750 | PBI->setMetadata(LLVMContext::MD_prof, NULL); |
Nick Lewycky | 06cc66f | 2011-12-27 04:31:52 +0000 | [diff] [blame] | 1751 | } |
| 1752 | } else { |
| 1753 | PBI->setMetadata(LLVMContext::MD_prof, NULL); |
| 1754 | } |
| 1755 | |
Chris Lattner | 3c6e746 | 2011-04-14 02:44:53 +0000 | [diff] [blame] | 1756 | // Copy any debug value intrinsics into the end of PredBlock. |
| 1757 | for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) |
| 1758 | if (isa<DbgInfoIntrinsic>(*I)) |
| 1759 | I->clone()->insertBefore(PBI); |
| 1760 | |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 1761 | return true; |
Chris Lattner | 1347e87 | 2008-07-13 21:12:01 +0000 | [diff] [blame] | 1762 | } |
| 1763 | return false; |
| 1764 | } |
| 1765 | |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1766 | /// SimplifyCondBranchToCondBranch - If we have a conditional branch as a |
| 1767 | /// predecessor of another block, this function tries to simplify it. We know |
| 1768 | /// that PBI and BI are both conditional branches, and BI is in one of the |
| 1769 | /// successor blocks of PBI - PBI branches to BI. |
| 1770 | static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { |
| 1771 | assert(PBI->isConditional() && BI->isConditional()); |
| 1772 | BasicBlock *BB = BI->getParent(); |
Dan Gohman | 4ae5126 | 2009-08-12 16:23:25 +0000 | [diff] [blame] | 1773 | |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1774 | // If this block ends with a branch instruction, and if there is a |
| 1775 | // predecessor that ends on a branch of the same condition, make |
| 1776 | // this conditional branch redundant. |
| 1777 | if (PBI->getCondition() == BI->getCondition() && |
| 1778 | PBI->getSuccessor(0) != PBI->getSuccessor(1)) { |
| 1779 | // Okay, the outcome of this conditional branch is statically |
| 1780 | // knowable. If this block had a single pred, handle specially. |
| 1781 | if (BB->getSinglePredecessor()) { |
| 1782 | // Turn this into a branch on constant. |
| 1783 | bool CondIsTrue = PBI->getSuccessor(0) == BB; |
Owen Anderson | 1d0be15 | 2009-08-13 21:58:54 +0000 | [diff] [blame] | 1784 | BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()), |
| 1785 | CondIsTrue)); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1786 | return true; // Nuke the branch on constant. |
| 1787 | } |
| 1788 | |
| 1789 | // Otherwise, if there are multiple predecessors, insert a PHI that merges |
| 1790 | // in the constant and simplify the block result. Subsequent passes of |
| 1791 | // simplifycfg will thread the block. |
| 1792 | if (BlockIsSimpleEnoughToThreadThrough(BB)) { |
Jay Foad | d8b4fb4 | 2011-03-30 11:19:20 +0000 | [diff] [blame] | 1793 | pred_iterator PB = pred_begin(BB), PE = pred_end(BB); |
Owen Anderson | 1d0be15 | 2009-08-13 21:58:54 +0000 | [diff] [blame] | 1794 | PHINode *NewPN = PHINode::Create(Type::getInt1Ty(BB->getContext()), |
Jay Foad | 3ecfc86 | 2011-03-30 11:28:46 +0000 | [diff] [blame] | 1795 | std::distance(PB, PE), |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1796 | BI->getCondition()->getName() + ".pr", |
| 1797 | BB->begin()); |
Chris Lattner | eb388af | 2008-07-13 21:55:46 +0000 | [diff] [blame] | 1798 | // Okay, we're going to insert the PHI node. Since PBI is not the only |
| 1799 | // predecessor, compute the PHI'd conditional value for all of the preds. |
| 1800 | // Any predecessor where the condition is not computable we keep symbolic. |
Jay Foad | d8b4fb4 | 2011-03-30 11:19:20 +0000 | [diff] [blame] | 1801 | for (pred_iterator PI = PB; PI != PE; ++PI) { |
Gabor Greif | 6253983 | 2010-07-12 10:59:23 +0000 | [diff] [blame] | 1802 | BasicBlock *P = *PI; |
| 1803 | if ((PBI = dyn_cast<BranchInst>(P->getTerminator())) && |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1804 | PBI != BI && PBI->isConditional() && |
| 1805 | PBI->getCondition() == BI->getCondition() && |
| 1806 | PBI->getSuccessor(0) != PBI->getSuccessor(1)) { |
| 1807 | bool CondIsTrue = PBI->getSuccessor(0) == BB; |
Owen Anderson | 1d0be15 | 2009-08-13 21:58:54 +0000 | [diff] [blame] | 1808 | NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()), |
Gabor Greif | 6253983 | 2010-07-12 10:59:23 +0000 | [diff] [blame] | 1809 | CondIsTrue), P); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1810 | } else { |
Gabor Greif | 6253983 | 2010-07-12 10:59:23 +0000 | [diff] [blame] | 1811 | NewPN->addIncoming(BI->getCondition(), P); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1812 | } |
Gabor Greif | 6253983 | 2010-07-12 10:59:23 +0000 | [diff] [blame] | 1813 | } |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1814 | |
| 1815 | BI->setCondition(NewPN); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1816 | return true; |
| 1817 | } |
| 1818 | } |
| 1819 | |
| 1820 | // If this is a conditional branch in an empty block, and if any |
| 1821 | // predecessors is a conditional branch to one of our destinations, |
| 1822 | // fold the conditions into logical ops and one cond br. |
Zhou Sheng | a8d57fe | 2009-02-26 06:56:37 +0000 | [diff] [blame] | 1823 | BasicBlock::iterator BBI = BB->begin(); |
| 1824 | // Ignore dbg intrinsics. |
| 1825 | while (isa<DbgInfoIntrinsic>(BBI)) |
| 1826 | ++BBI; |
| 1827 | if (&*BBI != BI) |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1828 | return false; |
Chris Lattner | 63bf29b | 2009-01-20 01:15:41 +0000 | [diff] [blame] | 1829 | |
| 1830 | |
| 1831 | if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BI->getCondition())) |
| 1832 | if (CE->canTrap()) |
| 1833 | return false; |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1834 | |
| 1835 | int PBIOp, BIOp; |
| 1836 | if (PBI->getSuccessor(0) == BI->getSuccessor(0)) |
| 1837 | PBIOp = BIOp = 0; |
| 1838 | else if (PBI->getSuccessor(0) == BI->getSuccessor(1)) |
| 1839 | PBIOp = 0, BIOp = 1; |
| 1840 | else if (PBI->getSuccessor(1) == BI->getSuccessor(0)) |
| 1841 | PBIOp = 1, BIOp = 0; |
| 1842 | else if (PBI->getSuccessor(1) == BI->getSuccessor(1)) |
| 1843 | PBIOp = BIOp = 1; |
| 1844 | else |
| 1845 | return false; |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1846 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1847 | // Check to make sure that the other destination of this branch |
| 1848 | // isn't BB itself. If so, this is an infinite loop that will |
| 1849 | // keep getting unwound. |
| 1850 | if (PBI->getSuccessor(PBIOp) == BB) |
| 1851 | return false; |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1852 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1853 | // Do not perform this transformation if it would require |
| 1854 | // insertion of a large number of select instructions. For targets |
| 1855 | // without predication/cmovs, this is a big pessimization. |
| 1856 | BasicBlock *CommonDest = PBI->getSuccessor(PBIOp); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1857 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1858 | unsigned NumPhis = 0; |
| 1859 | for (BasicBlock::iterator II = CommonDest->begin(); |
| 1860 | isa<PHINode>(II); ++II, ++NumPhis) |
| 1861 | if (NumPhis > 2) // Disable this xform. |
| 1862 | return false; |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1863 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1864 | // Finally, if everything is ok, fold the branches to logical ops. |
| 1865 | BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1); |
| 1866 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 1867 | DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent() |
Chris Lattner | bdff548 | 2009-08-23 04:37:46 +0000 | [diff] [blame] | 1868 | << "AND: " << *BI->getParent()); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1869 | |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 1870 | |
| 1871 | // If OtherDest *is* BB, then BB is a basic block with a single conditional |
| 1872 | // branch in it, where one edge (OtherDest) goes back to itself but the other |
| 1873 | // exits. We don't *know* that the program avoids the infinite loop |
| 1874 | // (even though that seems likely). If we do this xform naively, we'll end up |
| 1875 | // recursively unpeeling the loop. Since we know that (after the xform is |
| 1876 | // done) that the block *is* infinite if reached, we just make it an obviously |
| 1877 | // infinite loop with no cond branch. |
| 1878 | if (OtherDest == BB) { |
| 1879 | // Insert it at the end of the function, because it's either code, |
| 1880 | // or it won't matter if it's hot. :) |
Owen Anderson | 1d0be15 | 2009-08-13 21:58:54 +0000 | [diff] [blame] | 1881 | BasicBlock *InfLoopBlock = BasicBlock::Create(BB->getContext(), |
| 1882 | "infloop", BB->getParent()); |
Chris Lattner | 093a438 | 2008-07-13 22:23:11 +0000 | [diff] [blame] | 1883 | BranchInst::Create(InfLoopBlock, InfLoopBlock); |
| 1884 | OtherDest = InfLoopBlock; |
| 1885 | } |
| 1886 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 1887 | DEBUG(dbgs() << *PBI->getParent()->getParent()); |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1888 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1889 | // BI may have other predecessors. Because of this, we leave |
| 1890 | // it alone, but modify PBI. |
| 1891 | |
| 1892 | // Make sure we get to CommonDest on True&True directions. |
| 1893 | Value *PBICond = PBI->getCondition(); |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1894 | IRBuilder<true, NoFolder> Builder(PBI); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1895 | if (PBIOp) |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1896 | PBICond = Builder.CreateNot(PBICond, PBICond->getName()+".not"); |
| 1897 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1898 | Value *BICond = BI->getCondition(); |
| 1899 | if (BIOp) |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1900 | BICond = Builder.CreateNot(BICond, BICond->getName()+".not"); |
| 1901 | |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1902 | // Merge the conditions. |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1903 | Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge"); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1904 | |
| 1905 | // Modify PBI to branch on the new condition to the new dests. |
| 1906 | PBI->setCondition(Cond); |
| 1907 | PBI->setSuccessor(0, CommonDest); |
| 1908 | PBI->setSuccessor(1, OtherDest); |
| 1909 | |
| 1910 | // OtherDest may have phi nodes. If so, add an entry from PBI's |
| 1911 | // block that are identical to the entries for BI's block. |
Chris Lattner | 6de0a28 | 2010-12-14 07:09:42 +0000 | [diff] [blame] | 1912 | AddPredecessorToBlock(OtherDest, PBI->getParent(), BB); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1913 | |
| 1914 | // We know that the CommonDest already had an edge from PBI to |
| 1915 | // it. If it has PHIs though, the PHIs may have different |
| 1916 | // entries for BB and PBI's BB. If so, insert a select to make |
| 1917 | // them agree. |
Chris Lattner | 6de0a28 | 2010-12-14 07:09:42 +0000 | [diff] [blame] | 1918 | PHINode *PN; |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1919 | for (BasicBlock::iterator II = CommonDest->begin(); |
| 1920 | (PN = dyn_cast<PHINode>(II)); ++II) { |
| 1921 | Value *BIV = PN->getIncomingValueForBlock(BB); |
| 1922 | unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent()); |
| 1923 | Value *PBIV = PN->getIncomingValue(PBBIdx); |
| 1924 | if (BIV != PBIV) { |
| 1925 | // Insert a select in PBI to pick the right value. |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 1926 | Value *NV = cast<SelectInst> |
| 1927 | (Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName()+".mux")); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1928 | PN->setIncomingValue(PBBIdx, NV); |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1929 | } |
| 1930 | } |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1931 | |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 1932 | DEBUG(dbgs() << "INTO: " << *PBI->getParent()); |
| 1933 | DEBUG(dbgs() << *PBI->getParent()->getParent()); |
Chris Lattner | b824512 | 2008-07-13 22:04:41 +0000 | [diff] [blame] | 1934 | |
| 1935 | // This basic block is probably dead. We know it has at least |
| 1936 | // one fewer predecessor. |
| 1937 | return true; |
Chris Lattner | 867661a | 2008-07-13 21:53:26 +0000 | [diff] [blame] | 1938 | } |
| 1939 | |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1940 | // SimplifyTerminatorOnSelect - Simplifies a terminator by replacing it with a |
| 1941 | // branch to TrueBB if Cond is true or to FalseBB if Cond is false. |
| 1942 | // Takes care of updating the successors and removing the old terminator. |
| 1943 | // Also makes sure not to introduce new successors by assuming that edges to |
| 1944 | // non-successor TrueBBs and FalseBBs aren't reachable. |
| 1945 | static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond, |
| 1946 | BasicBlock *TrueBB, BasicBlock *FalseBB){ |
| 1947 | // Remove any superfluous successor edges from the CFG. |
| 1948 | // First, figure out which successors to preserve. |
| 1949 | // If TrueBB and FalseBB are equal, only try to preserve one copy of that |
| 1950 | // successor. |
| 1951 | BasicBlock *KeepEdge1 = TrueBB; |
| 1952 | BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : 0; |
| 1953 | |
| 1954 | // Then remove the rest. |
| 1955 | for (unsigned I = 0, E = OldTerm->getNumSuccessors(); I != E; ++I) { |
| 1956 | BasicBlock *Succ = OldTerm->getSuccessor(I); |
| 1957 | // Make sure only to keep exactly one copy of each edge. |
| 1958 | if (Succ == KeepEdge1) |
| 1959 | KeepEdge1 = 0; |
| 1960 | else if (Succ == KeepEdge2) |
| 1961 | KeepEdge2 = 0; |
| 1962 | else |
| 1963 | Succ->removePredecessor(OldTerm->getParent()); |
| 1964 | } |
| 1965 | |
Devang Patel | d3372b8 | 2011-05-18 18:43:31 +0000 | [diff] [blame] | 1966 | IRBuilder<> Builder(OldTerm); |
| 1967 | Builder.SetCurrentDebugLocation(OldTerm->getDebugLoc()); |
| 1968 | |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1969 | // Insert an appropriate new terminator. |
| 1970 | if ((KeepEdge1 == 0) && (KeepEdge2 == 0)) { |
| 1971 | if (TrueBB == FalseBB) |
| 1972 | // We were only looking for one successor, and it was present. |
| 1973 | // Create an unconditional branch to it. |
Devang Patel | d3372b8 | 2011-05-18 18:43:31 +0000 | [diff] [blame] | 1974 | Builder.CreateBr(TrueBB); |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1975 | else |
| 1976 | // We found both of the successors we were looking for. |
| 1977 | // Create a conditional branch sharing the condition of the select. |
Devang Patel | d3372b8 | 2011-05-18 18:43:31 +0000 | [diff] [blame] | 1978 | Builder.CreateCondBr(Cond, TrueBB, FalseBB); |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1979 | } else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) { |
| 1980 | // Neither of the selected blocks were successors, so this |
| 1981 | // terminator must be unreachable. |
| 1982 | new UnreachableInst(OldTerm->getContext(), OldTerm); |
| 1983 | } else { |
| 1984 | // One of the selected values was a successor, but the other wasn't. |
| 1985 | // Insert an unconditional branch to the one that was found; |
| 1986 | // the edge to the one that wasn't must be unreachable. |
| 1987 | if (KeepEdge1 == 0) |
| 1988 | // Only TrueBB was found. |
Devang Patel | d3372b8 | 2011-05-18 18:43:31 +0000 | [diff] [blame] | 1989 | Builder.CreateBr(TrueBB); |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1990 | else |
| 1991 | // Only FalseBB was found. |
Devang Patel | d3372b8 | 2011-05-18 18:43:31 +0000 | [diff] [blame] | 1992 | Builder.CreateBr(FalseBB); |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 1993 | } |
| 1994 | |
| 1995 | EraseTerminatorInstAndDCECond(OldTerm); |
| 1996 | return true; |
| 1997 | } |
| 1998 | |
Frits van Bommel | f7b2a9d | 2011-02-28 09:44:07 +0000 | [diff] [blame] | 1999 | // SimplifySwitchOnSelect - Replaces |
| 2000 | // (switch (select cond, X, Y)) on constant X, Y |
| 2001 | // with a branch - conditional if X and Y lead to distinct BBs, |
| 2002 | // unconditional otherwise. |
| 2003 | static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) { |
| 2004 | // Check for constant integer values in the select. |
| 2005 | ConstantInt *TrueVal = dyn_cast<ConstantInt>(Select->getTrueValue()); |
| 2006 | ConstantInt *FalseVal = dyn_cast<ConstantInt>(Select->getFalseValue()); |
| 2007 | if (!TrueVal || !FalseVal) |
| 2008 | return false; |
| 2009 | |
| 2010 | // Find the relevant condition and destinations. |
| 2011 | Value *Condition = Select->getCondition(); |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2012 | BasicBlock *TrueBB = SI->findCaseValue(TrueVal).getCaseSuccessor(); |
| 2013 | BasicBlock *FalseBB = SI->findCaseValue(FalseVal).getCaseSuccessor(); |
Frits van Bommel | f7b2a9d | 2011-02-28 09:44:07 +0000 | [diff] [blame] | 2014 | |
| 2015 | // Perform the actual simplification. |
| 2016 | return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB); |
| 2017 | } |
| 2018 | |
Frits van Bommel | 7ac40c3 | 2010-12-05 18:29:03 +0000 | [diff] [blame] | 2019 | // SimplifyIndirectBrOnSelect - Replaces |
| 2020 | // (indirectbr (select cond, blockaddress(@fn, BlockA), |
| 2021 | // blockaddress(@fn, BlockB))) |
| 2022 | // with |
| 2023 | // (br cond, BlockA, BlockB). |
| 2024 | static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { |
| 2025 | // Check that both operands of the select are block addresses. |
| 2026 | BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue()); |
| 2027 | BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue()); |
| 2028 | if (!TBA || !FBA) |
| 2029 | return false; |
| 2030 | |
| 2031 | // Extract the actual blocks. |
| 2032 | BasicBlock *TrueBB = TBA->getBasicBlock(); |
| 2033 | BasicBlock *FalseBB = FBA->getBasicBlock(); |
| 2034 | |
Frits van Bommel | 65fdded | 2011-01-11 12:52:11 +0000 | [diff] [blame] | 2035 | // Perform the actual simplification. |
| 2036 | return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB); |
Frits van Bommel | 7ac40c3 | 2010-12-05 18:29:03 +0000 | [diff] [blame] | 2037 | } |
| 2038 | |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2039 | /// TryToSimplifyUncondBranchWithICmpInIt - This is called when we find an icmp |
| 2040 | /// instruction (a seteq/setne with a constant) as the only instruction in a |
| 2041 | /// block that ends with an uncond branch. We are looking for a very specific |
| 2042 | /// pattern that occurs when "A == 1 || A == 2 || A == 3" gets simplified. In |
| 2043 | /// this case, we merge the first two "or's of icmp" into a switch, but then the |
| 2044 | /// default value goes to an uncond block with a seteq in it, we get something |
| 2045 | /// like: |
| 2046 | /// |
| 2047 | /// switch i8 %A, label %DEFAULT [ i8 1, label %end i8 2, label %end ] |
| 2048 | /// DEFAULT: |
| 2049 | /// %tmp = icmp eq i8 %A, 92 |
| 2050 | /// br label %end |
| 2051 | /// end: |
| 2052 | /// ... = phi i1 [ true, %entry ], [ %tmp, %DEFAULT ], [ true, %entry ] |
| 2053 | /// |
| 2054 | /// We prefer to split the edge to 'end' so that there is a true/false entry to |
| 2055 | /// the PHI, merging the third icmp into the switch. |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2056 | static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 2057 | const TargetData *TD, |
| 2058 | IRBuilder<> &Builder) { |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2059 | BasicBlock *BB = ICI->getParent(); |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 2060 | |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2061 | // If the block has any PHIs in it or the icmp has multiple uses, it is too |
| 2062 | // complex. |
| 2063 | if (isa<PHINode>(BB->begin()) || !ICI->hasOneUse()) return false; |
| 2064 | |
| 2065 | Value *V = ICI->getOperand(0); |
| 2066 | ConstantInt *Cst = cast<ConstantInt>(ICI->getOperand(1)); |
| 2067 | |
| 2068 | // The pattern we're looking for is where our only predecessor is a switch on |
| 2069 | // 'V' and this block is the default case for the switch. In this case we can |
| 2070 | // fold the compared value into the switch to simplify things. |
| 2071 | BasicBlock *Pred = BB->getSinglePredecessor(); |
| 2072 | if (Pred == 0 || !isa<SwitchInst>(Pred->getTerminator())) return false; |
| 2073 | |
| 2074 | SwitchInst *SI = cast<SwitchInst>(Pred->getTerminator()); |
| 2075 | if (SI->getCondition() != V) |
| 2076 | return false; |
| 2077 | |
| 2078 | // If BB is reachable on a non-default case, then we simply know the value of |
| 2079 | // V in this block. Substitute it and constant fold the icmp instruction |
| 2080 | // away. |
| 2081 | if (SI->getDefaultDest() != BB) { |
| 2082 | ConstantInt *VVal = SI->findCaseDest(BB); |
| 2083 | assert(VVal && "Should have a unique destination value"); |
| 2084 | ICI->setOperand(0, VVal); |
| 2085 | |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2086 | if (Value *V = SimplifyInstruction(ICI, TD)) { |
| 2087 | ICI->replaceAllUsesWith(V); |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2088 | ICI->eraseFromParent(); |
| 2089 | } |
| 2090 | // BB is now empty, so it is likely to simplify away. |
| 2091 | return SimplifyCFG(BB) | true; |
| 2092 | } |
| 2093 | |
Chris Lattner | abf7067 | 2010-12-13 03:43:57 +0000 | [diff] [blame] | 2094 | // Ok, the block is reachable from the default dest. If the constant we're |
| 2095 | // comparing exists in one of the other edges, then we can constant fold ICI |
| 2096 | // and zap it. |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2097 | if (SI->findCaseValue(Cst) != SI->caseDefault()) { |
Chris Lattner | abf7067 | 2010-12-13 03:43:57 +0000 | [diff] [blame] | 2098 | Value *V; |
| 2099 | if (ICI->getPredicate() == ICmpInst::ICMP_EQ) |
| 2100 | V = ConstantInt::getFalse(BB->getContext()); |
| 2101 | else |
| 2102 | V = ConstantInt::getTrue(BB->getContext()); |
| 2103 | |
| 2104 | ICI->replaceAllUsesWith(V); |
| 2105 | ICI->eraseFromParent(); |
| 2106 | // BB is now empty, so it is likely to simplify away. |
| 2107 | return SimplifyCFG(BB) | true; |
| 2108 | } |
| 2109 | |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2110 | // The use of the icmp has to be in the 'end' block, by the only PHI node in |
| 2111 | // the block. |
| 2112 | BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0); |
| 2113 | PHINode *PHIUse = dyn_cast<PHINode>(ICI->use_back()); |
| 2114 | if (PHIUse == 0 || PHIUse != &SuccBlock->front() || |
| 2115 | isa<PHINode>(++BasicBlock::iterator(PHIUse))) |
| 2116 | return false; |
| 2117 | |
| 2118 | // If the icmp is a SETEQ, then the default dest gets false, the new edge gets |
| 2119 | // true in the PHI. |
| 2120 | Constant *DefaultCst = ConstantInt::getTrue(BB->getContext()); |
| 2121 | Constant *NewCst = ConstantInt::getFalse(BB->getContext()); |
| 2122 | |
| 2123 | if (ICI->getPredicate() == ICmpInst::ICMP_EQ) |
| 2124 | std::swap(DefaultCst, NewCst); |
| 2125 | |
| 2126 | // Replace ICI (which is used by the PHI for the default value) with true or |
| 2127 | // false depending on if it is EQ or NE. |
| 2128 | ICI->replaceAllUsesWith(DefaultCst); |
| 2129 | ICI->eraseFromParent(); |
| 2130 | |
| 2131 | // Okay, the switch goes to this block on a default value. Add an edge from |
| 2132 | // the switch to the merge point on the compared value. |
| 2133 | BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "switch.edge", |
| 2134 | BB->getParent(), BB); |
| 2135 | SI->addCase(Cst, NewBB); |
| 2136 | |
| 2137 | // NewBB branches to the phi block, add the uncond branch and the phi entry. |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 2138 | Builder.SetInsertPoint(NewBB); |
| 2139 | Builder.SetCurrentDebugLocation(SI->getDebugLoc()); |
| 2140 | Builder.CreateBr(SuccBlock); |
Chris Lattner | 61c7744 | 2010-12-13 03:18:54 +0000 | [diff] [blame] | 2141 | PHIUse->addIncoming(NewCst, NewBB); |
| 2142 | return true; |
| 2143 | } |
| 2144 | |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2145 | /// SimplifyBranchOnICmpChain - The specified branch is a conditional branch. |
| 2146 | /// Check to see if it is branching on an or/and chain of icmp instructions, and |
| 2147 | /// fold it into a switch instruction if so. |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2148 | static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, |
| 2149 | IRBuilder<> &Builder) { |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2150 | Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()); |
| 2151 | if (Cond == 0) return false; |
| 2152 | |
| 2153 | |
| 2154 | // Change br (X == 0 | X == 1), T, F into a switch instruction. |
| 2155 | // If this is a bunch of seteq's or'd together, or if it's a bunch of |
| 2156 | // 'setne's and'ed together, collect them. |
| 2157 | Value *CompVal = 0; |
| 2158 | std::vector<ConstantInt*> Values; |
| 2159 | bool TrueWhenEqual = true; |
| 2160 | Value *ExtraCase = 0; |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 2161 | unsigned UsedICmps = 0; |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2162 | |
| 2163 | if (Cond->getOpcode() == Instruction::Or) { |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 2164 | CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true, |
| 2165 | UsedICmps); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2166 | } else if (Cond->getOpcode() == Instruction::And) { |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 2167 | CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false, |
| 2168 | UsedICmps); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2169 | TrueWhenEqual = false; |
| 2170 | } |
| 2171 | |
| 2172 | // If we didn't have a multiply compared value, fail. |
| 2173 | if (CompVal == 0) return false; |
| 2174 | |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 2175 | // Avoid turning single icmps into a switch. |
| 2176 | if (UsedICmps <= 1) |
| 2177 | return false; |
| 2178 | |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2179 | // There might be duplicate constants in the list, which the switch |
| 2180 | // instruction can't handle, remove them now. |
| 2181 | array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate); |
| 2182 | Values.erase(std::unique(Values.begin(), Values.end()), Values.end()); |
| 2183 | |
| 2184 | // If Extra was used, we require at least two switch values to do the |
| 2185 | // transformation. A switch with one value is just an cond branch. |
| 2186 | if (ExtraCase && Values.size() < 2) return false; |
| 2187 | |
| 2188 | // Figure out which block is which destination. |
| 2189 | BasicBlock *DefaultBB = BI->getSuccessor(1); |
| 2190 | BasicBlock *EdgeBB = BI->getSuccessor(0); |
| 2191 | if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB); |
| 2192 | |
| 2193 | BasicBlock *BB = BI->getParent(); |
| 2194 | |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2195 | DEBUG(dbgs() << "Converting 'icmp' chain with " << Values.size() |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 2196 | << " cases into SWITCH. BB is:\n" << *BB); |
| 2197 | |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2198 | // If there are any extra values that couldn't be folded into the switch |
| 2199 | // then we evaluate them with an explicit branch first. Split the block |
| 2200 | // right before the condbr to handle it. |
| 2201 | if (ExtraCase) { |
| 2202 | BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test"); |
| 2203 | // Remove the uncond branch added to the old block. |
| 2204 | TerminatorInst *OldTI = BB->getTerminator(); |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2205 | Builder.SetInsertPoint(OldTI); |
| 2206 | |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 2207 | if (TrueWhenEqual) |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2208 | Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB); |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 2209 | else |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2210 | Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB); |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 2211 | |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2212 | OldTI->eraseFromParent(); |
Chris Lattner | 97bd89e | 2010-12-13 05:34:18 +0000 | [diff] [blame] | 2213 | |
| 2214 | // If there are PHI nodes in EdgeBB, then we need to add a new entry to them |
| 2215 | // for the edge we just added. |
Chris Lattner | 6de0a28 | 2010-12-14 07:09:42 +0000 | [diff] [blame] | 2216 | AddPredecessorToBlock(EdgeBB, BB, NewBB); |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2217 | |
| 2218 | DEBUG(dbgs() << " ** 'icmp' chain unhandled condition: " << *ExtraCase |
| 2219 | << "\nEXTRABB = " << *BB); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2220 | BB = NewBB; |
| 2221 | } |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2222 | |
| 2223 | Builder.SetInsertPoint(BI); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2224 | // Convert pointer to int before we switch. |
| 2225 | if (CompVal->getType()->isPointerTy()) { |
| 2226 | assert(TD && "Cannot switch on pointer without TargetData"); |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2227 | CompVal = Builder.CreatePtrToInt(CompVal, |
| 2228 | TD->getIntPtrType(CompVal->getContext()), |
| 2229 | "magicptr"); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2230 | } |
| 2231 | |
| 2232 | // Create the new switch instruction now. |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2233 | SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size()); |
Devang Patel | d80e8ed | 2011-05-17 23:29:05 +0000 | [diff] [blame] | 2234 | |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2235 | // Add all of the 'cases' to the switch instruction. |
| 2236 | for (unsigned i = 0, e = Values.size(); i != e; ++i) |
| 2237 | New->addCase(Values[i], EdgeBB); |
| 2238 | |
| 2239 | // We added edges from PI to the EdgeBB. As such, if there were any |
| 2240 | // PHI nodes in EdgeBB, they need entries to be added corresponding to |
| 2241 | // the number of edges added. |
| 2242 | for (BasicBlock::iterator BBI = EdgeBB->begin(); |
| 2243 | isa<PHINode>(BBI); ++BBI) { |
| 2244 | PHINode *PN = cast<PHINode>(BBI); |
| 2245 | Value *InVal = PN->getIncomingValueForBlock(BB); |
| 2246 | for (unsigned i = 0, e = Values.size()-1; i != e; ++i) |
| 2247 | PN->addIncoming(InVal, BB); |
| 2248 | } |
| 2249 | |
| 2250 | // Erase the old branch instruction. |
| 2251 | EraseTerminatorInstAndDCECond(BI); |
Chris Lattner | 117f8cf | 2010-12-14 05:57:30 +0000 | [diff] [blame] | 2252 | |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2253 | DEBUG(dbgs() << " ** 'icmp' chain result is:\n" << *BB << '\n'); |
Chris Lattner | 97fdb89 | 2010-12-13 05:03:41 +0000 | [diff] [blame] | 2254 | return true; |
| 2255 | } |
| 2256 | |
Duncan Sands | ad99ef8 | 2011-09-05 12:57:57 +0000 | [diff] [blame] | 2257 | bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) { |
| 2258 | // If this is a trivial landing pad that just continues unwinding the caught |
| 2259 | // exception then zap the landing pad, turning its invokes into calls. |
| 2260 | BasicBlock *BB = RI->getParent(); |
| 2261 | LandingPadInst *LPInst = dyn_cast<LandingPadInst>(BB->getFirstNonPHI()); |
| 2262 | if (RI->getValue() != LPInst) |
| 2263 | // Not a landing pad, or the resume is not unwinding the exception that |
| 2264 | // caused control to branch here. |
| 2265 | return false; |
| 2266 | |
| 2267 | // Check that there are no other instructions except for debug intrinsics. |
| 2268 | BasicBlock::iterator I = LPInst, E = RI; |
| 2269 | while (++I != E) |
| 2270 | if (!isa<DbgInfoIntrinsic>(I)) |
| 2271 | return false; |
| 2272 | |
| 2273 | // Turn all invokes that unwind here into calls and delete the basic block. |
| 2274 | for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) { |
| 2275 | InvokeInst *II = cast<InvokeInst>((*PI++)->getTerminator()); |
| 2276 | SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3); |
| 2277 | // Insert a call instruction before the invoke. |
| 2278 | CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II); |
| 2279 | Call->takeName(II); |
| 2280 | Call->setCallingConv(II->getCallingConv()); |
| 2281 | Call->setAttributes(II->getAttributes()); |
| 2282 | Call->setDebugLoc(II->getDebugLoc()); |
| 2283 | |
| 2284 | // Anything that used the value produced by the invoke instruction now uses |
| 2285 | // the value produced by the call instruction. Note that we do this even |
| 2286 | // for void functions and calls with no uses so that the callgraph edge is |
| 2287 | // updated. |
| 2288 | II->replaceAllUsesWith(Call); |
| 2289 | BB->removePredecessor(II->getParent()); |
| 2290 | |
| 2291 | // Insert a branch to the normal destination right before the invoke. |
| 2292 | BranchInst::Create(II->getNormalDest(), II); |
| 2293 | |
| 2294 | // Finally, delete the invoke instruction! |
| 2295 | II->eraseFromParent(); |
| 2296 | } |
| 2297 | |
| 2298 | // The landingpad is now unreachable. Zap it. |
| 2299 | BB->eraseFromParent(); |
| 2300 | return true; |
| 2301 | } |
| 2302 | |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 2303 | bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2304 | BasicBlock *BB = RI->getParent(); |
| 2305 | if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false; |
| 2306 | |
| 2307 | // Find predecessors that end with branches. |
| 2308 | SmallVector<BasicBlock*, 8> UncondBranchPreds; |
| 2309 | SmallVector<BranchInst*, 8> CondBranchPreds; |
| 2310 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { |
| 2311 | BasicBlock *P = *PI; |
| 2312 | TerminatorInst *PTI = P->getTerminator(); |
| 2313 | if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) { |
| 2314 | if (BI->isUnconditional()) |
| 2315 | UncondBranchPreds.push_back(P); |
| 2316 | else |
| 2317 | CondBranchPreds.push_back(BI); |
| 2318 | } |
| 2319 | } |
| 2320 | |
| 2321 | // If we found some, do the transformation! |
Evan Cheng | c3f507f | 2011-01-29 04:46:23 +0000 | [diff] [blame] | 2322 | if (!UncondBranchPreds.empty() && DupRet) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2323 | while (!UncondBranchPreds.empty()) { |
| 2324 | BasicBlock *Pred = UncondBranchPreds.pop_back_val(); |
| 2325 | DEBUG(dbgs() << "FOLDING: " << *BB |
| 2326 | << "INTO UNCOND BRANCH PRED: " << *Pred); |
Evan Cheng | c3f507f | 2011-01-29 04:46:23 +0000 | [diff] [blame] | 2327 | (void)FoldReturnIntoUncondBranch(RI, BB, Pred); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2328 | } |
| 2329 | |
| 2330 | // If we eliminated all predecessors of the block, delete the block now. |
| 2331 | if (pred_begin(BB) == pred_end(BB)) |
| 2332 | // We know there are no successors, so just nuke the block. |
| 2333 | BB->eraseFromParent(); |
| 2334 | |
| 2335 | return true; |
| 2336 | } |
| 2337 | |
| 2338 | // Check out all of the conditional branches going to this return |
| 2339 | // instruction. If any of them just select between returns, change the |
| 2340 | // branch itself into a select/return pair. |
| 2341 | while (!CondBranchPreds.empty()) { |
| 2342 | BranchInst *BI = CondBranchPreds.pop_back_val(); |
| 2343 | |
| 2344 | // Check to see if the non-BB successor is also a return block. |
| 2345 | if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) && |
| 2346 | isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) && |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 2347 | SimplifyCondBranchToTwoReturns(BI, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2348 | return true; |
| 2349 | } |
| 2350 | return false; |
| 2351 | } |
| 2352 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2353 | bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { |
| 2354 | BasicBlock *BB = UI->getParent(); |
| 2355 | |
| 2356 | bool Changed = false; |
| 2357 | |
| 2358 | // If there are any instructions immediately before the unreachable that can |
| 2359 | // be removed, do so. |
| 2360 | while (UI != BB->begin()) { |
| 2361 | BasicBlock::iterator BBI = UI; |
| 2362 | --BBI; |
Eli Friedman | 8176388 | 2011-08-15 23:59:28 +0000 | [diff] [blame] | 2363 | // Do not delete instructions that can have side effects which might cause |
| 2364 | // the unreachable to not be reachable; specifically, calls and volatile |
| 2365 | // operations may have this effect. |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2366 | if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break; |
Eli Friedman | 8176388 | 2011-08-15 23:59:28 +0000 | [diff] [blame] | 2367 | |
| 2368 | if (BBI->mayHaveSideEffects()) { |
| 2369 | if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) { |
| 2370 | if (SI->isVolatile()) |
| 2371 | break; |
| 2372 | } else if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) { |
| 2373 | if (LI->isVolatile()) |
| 2374 | break; |
| 2375 | } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(BBI)) { |
| 2376 | if (RMWI->isVolatile()) |
| 2377 | break; |
| 2378 | } else if (AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(BBI)) { |
| 2379 | if (CXI->isVolatile()) |
| 2380 | break; |
| 2381 | } else if (!isa<FenceInst>(BBI) && !isa<VAArgInst>(BBI) && |
| 2382 | !isa<LandingPadInst>(BBI)) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2383 | break; |
Eli Friedman | 8176388 | 2011-08-15 23:59:28 +0000 | [diff] [blame] | 2384 | } |
Bill Wendling | 23b49ba | 2011-08-16 20:41:17 +0000 | [diff] [blame] | 2385 | // Note that deleting LandingPad's here is in fact okay, although it |
| 2386 | // involves a bit of subtle reasoning. If this inst is a LandingPad, |
| 2387 | // all the predecessors of this block will be the unwind edges of Invokes, |
| 2388 | // and we can therefore guarantee this block will be erased. |
Eli Friedman | 8176388 | 2011-08-15 23:59:28 +0000 | [diff] [blame] | 2389 | } |
| 2390 | |
Eli Friedman | 2adc5b6 | 2011-03-09 00:48:33 +0000 | [diff] [blame] | 2391 | // Delete this instruction (any uses are guaranteed to be dead) |
| 2392 | if (!BBI->use_empty()) |
| 2393 | BBI->replaceAllUsesWith(UndefValue::get(BBI->getType())); |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2394 | BBI->eraseFromParent(); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2395 | Changed = true; |
| 2396 | } |
| 2397 | |
| 2398 | // If the unreachable instruction is the first in the block, take a gander |
| 2399 | // at all of the predecessors of this instruction, and simplify them. |
| 2400 | if (&BB->front() != UI) return Changed; |
| 2401 | |
| 2402 | SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB)); |
| 2403 | for (unsigned i = 0, e = Preds.size(); i != e; ++i) { |
| 2404 | TerminatorInst *TI = Preds[i]->getTerminator(); |
Devang Patel | 1aa89a2 | 2011-05-19 00:09:21 +0000 | [diff] [blame] | 2405 | IRBuilder<> Builder(TI); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2406 | if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { |
| 2407 | if (BI->isUnconditional()) { |
| 2408 | if (BI->getSuccessor(0) == BB) { |
| 2409 | new UnreachableInst(TI->getContext(), TI); |
| 2410 | TI->eraseFromParent(); |
| 2411 | Changed = true; |
| 2412 | } |
| 2413 | } else { |
| 2414 | if (BI->getSuccessor(0) == BB) { |
Devang Patel | 1aa89a2 | 2011-05-19 00:09:21 +0000 | [diff] [blame] | 2415 | Builder.CreateBr(BI->getSuccessor(1)); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2416 | EraseTerminatorInstAndDCECond(BI); |
| 2417 | } else if (BI->getSuccessor(1) == BB) { |
Devang Patel | 1aa89a2 | 2011-05-19 00:09:21 +0000 | [diff] [blame] | 2418 | Builder.CreateBr(BI->getSuccessor(0)); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2419 | EraseTerminatorInstAndDCECond(BI); |
| 2420 | Changed = true; |
| 2421 | } |
| 2422 | } |
| 2423 | } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2424 | for (SwitchInst::CaseIt i = SI->caseBegin(), e = SI->caseEnd(); |
| 2425 | i != e; ++i) |
| 2426 | if (i.getCaseSuccessor() == BB) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2427 | BB->removePredecessor(SI->getParent()); |
| 2428 | SI->removeCase(i); |
| 2429 | --i; --e; |
| 2430 | Changed = true; |
| 2431 | } |
| 2432 | // If the default value is unreachable, figure out the most popular |
| 2433 | // destination and make it the default. |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2434 | if (SI->getDefaultDest() == BB) { |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2435 | std::map<BasicBlock*, std::pair<unsigned, unsigned> > Popularity; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2436 | for (SwitchInst::CaseIt i = SI->caseBegin(), e = SI->caseEnd(); |
| 2437 | i != e; ++i) { |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 2438 | std::pair<unsigned, unsigned> &entry = |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2439 | Popularity[i.getCaseSuccessor()]; |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2440 | if (entry.first == 0) { |
| 2441 | entry.first = 1; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2442 | entry.second = i.getCaseIndex(); |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2443 | } else { |
| 2444 | entry.first++; |
| 2445 | } |
| 2446 | } |
| 2447 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2448 | // Find the most popular block. |
| 2449 | unsigned MaxPop = 0; |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2450 | unsigned MaxIndex = 0; |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2451 | BasicBlock *MaxBlock = 0; |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2452 | for (std::map<BasicBlock*, std::pair<unsigned, unsigned> >::iterator |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2453 | I = Popularity.begin(), E = Popularity.end(); I != E; ++I) { |
Eli Friedman | b1a6eab | 2011-03-15 02:23:35 +0000 | [diff] [blame] | 2454 | if (I->second.first > MaxPop || |
| 2455 | (I->second.first == MaxPop && MaxIndex > I->second.second)) { |
| 2456 | MaxPop = I->second.first; |
| 2457 | MaxIndex = I->second.second; |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2458 | MaxBlock = I->first; |
| 2459 | } |
| 2460 | } |
| 2461 | if (MaxBlock) { |
| 2462 | // Make this the new default, allowing us to delete any explicit |
| 2463 | // edges to it. |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2464 | SI->setDefaultDest(MaxBlock); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2465 | Changed = true; |
| 2466 | |
| 2467 | // If MaxBlock has phinodes in it, remove MaxPop-1 entries from |
| 2468 | // it. |
| 2469 | if (isa<PHINode>(MaxBlock->begin())) |
| 2470 | for (unsigned i = 0; i != MaxPop-1; ++i) |
| 2471 | MaxBlock->removePredecessor(SI->getParent()); |
| 2472 | |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2473 | for (SwitchInst::CaseIt i = SI->caseBegin(), e = SI->caseEnd(); |
| 2474 | i != e; ++i) |
| 2475 | if (i.getCaseSuccessor() == MaxBlock) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2476 | SI->removeCase(i); |
| 2477 | --i; --e; |
| 2478 | } |
| 2479 | } |
| 2480 | } |
| 2481 | } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) { |
| 2482 | if (II->getUnwindDest() == BB) { |
| 2483 | // Convert the invoke to a call instruction. This would be a good |
| 2484 | // place to note that the call does not throw though. |
Devang Patel | 1aa89a2 | 2011-05-19 00:09:21 +0000 | [diff] [blame] | 2485 | BranchInst *BI = Builder.CreateBr(II->getNormalDest()); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2486 | II->removeFromParent(); // Take out of symbol table |
| 2487 | |
| 2488 | // Insert the call now... |
| 2489 | SmallVector<Value*, 8> Args(II->op_begin(), II->op_end()-3); |
Devang Patel | 1aa89a2 | 2011-05-19 00:09:21 +0000 | [diff] [blame] | 2490 | Builder.SetInsertPoint(BI); |
| 2491 | CallInst *CI = Builder.CreateCall(II->getCalledValue(), |
Jay Foad | a3efbb1 | 2011-07-15 08:37:34 +0000 | [diff] [blame] | 2492 | Args, II->getName()); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2493 | CI->setCallingConv(II->getCallingConv()); |
| 2494 | CI->setAttributes(II->getAttributes()); |
| 2495 | // If the invoke produced a value, the call does now instead. |
| 2496 | II->replaceAllUsesWith(CI); |
| 2497 | delete II; |
| 2498 | Changed = true; |
| 2499 | } |
| 2500 | } |
| 2501 | } |
| 2502 | |
| 2503 | // If this block is now dead, remove it. |
| 2504 | if (pred_begin(BB) == pred_end(BB) && |
| 2505 | BB != &BB->getParent()->getEntryBlock()) { |
| 2506 | // We know there are no successors, so just nuke the block. |
| 2507 | BB->eraseFromParent(); |
| 2508 | return true; |
| 2509 | } |
| 2510 | |
| 2511 | return Changed; |
| 2512 | } |
| 2513 | |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2514 | /// TurnSwitchRangeIntoICmp - Turns a switch with that contains only a |
| 2515 | /// integer range comparison into a sub, an icmp and a branch. |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2516 | static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) { |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2517 | assert(SI->getNumCases() > 1 && "Degenerate switch?"); |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2518 | |
Benjamin Kramer | 042b27f | 2011-02-03 22:51:41 +0000 | [diff] [blame] | 2519 | // Make sure all cases point to the same destination and gather the values. |
| 2520 | SmallVector<ConstantInt *, 16> Cases; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2521 | SwitchInst::CaseIt I = SI->caseBegin(); |
| 2522 | Cases.push_back(I.getCaseValue()); |
| 2523 | SwitchInst::CaseIt PrevI = I++; |
| 2524 | for (SwitchInst::CaseIt E = SI->caseEnd(); I != E; PrevI = I++) { |
| 2525 | if (PrevI.getCaseSuccessor() != I.getCaseSuccessor()) |
Benjamin Kramer | 042b27f | 2011-02-03 22:51:41 +0000 | [diff] [blame] | 2526 | return false; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2527 | Cases.push_back(I.getCaseValue()); |
Benjamin Kramer | 042b27f | 2011-02-03 22:51:41 +0000 | [diff] [blame] | 2528 | } |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2529 | assert(Cases.size() == SI->getNumCases() && "Not all cases gathered"); |
Benjamin Kramer | 042b27f | 2011-02-03 22:51:41 +0000 | [diff] [blame] | 2530 | |
| 2531 | // Sort the case values, then check if they form a range we can transform. |
| 2532 | array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate); |
| 2533 | for (unsigned I = 1, E = Cases.size(); I != E; ++I) { |
| 2534 | if (Cases[I-1]->getValue() != Cases[I]->getValue()+1) |
| 2535 | return false; |
| 2536 | } |
| 2537 | |
| 2538 | Constant *Offset = ConstantExpr::getNeg(Cases.back()); |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2539 | Constant *NumCases = ConstantInt::get(Offset->getType(), SI->getNumCases()); |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2540 | |
Benjamin Kramer | 33828bc | 2011-02-07 22:37:28 +0000 | [diff] [blame] | 2541 | Value *Sub = SI->getCondition(); |
| 2542 | if (!Offset->isNullValue()) |
Devang Patel | 1f5812b | 2011-05-19 00:13:33 +0000 | [diff] [blame] | 2543 | Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off"); |
| 2544 | Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch"); |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2545 | Builder.CreateCondBr( |
| 2546 | Cmp, SI->caseBegin().getCaseSuccessor(), SI->getDefaultDest()); |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2547 | |
| 2548 | // Prune obsolete incoming values off the successor's PHI nodes. |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2549 | for (BasicBlock::iterator BBI = SI->caseBegin().getCaseSuccessor()->begin(); |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2550 | isa<PHINode>(BBI); ++BBI) { |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2551 | for (unsigned I = 0, E = SI->getNumCases()-1; I != E; ++I) |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2552 | cast<PHINode>(BBI)->removeIncomingValue(SI->getParent()); |
| 2553 | } |
| 2554 | SI->eraseFromParent(); |
| 2555 | |
| 2556 | return true; |
| 2557 | } |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2558 | |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2559 | /// EliminateDeadSwitchCases - Compute masked bits for the condition of a switch |
| 2560 | /// and use it to remove dead cases. |
| 2561 | static bool EliminateDeadSwitchCases(SwitchInst *SI) { |
| 2562 | Value *Cond = SI->getCondition(); |
| 2563 | unsigned Bits = cast<IntegerType>(Cond->getType())->getBitWidth(); |
| 2564 | APInt KnownZero(Bits, 0), KnownOne(Bits, 0); |
| 2565 | ComputeMaskedBits(Cond, APInt::getAllOnesValue(Bits), KnownZero, KnownOne); |
| 2566 | |
| 2567 | // Gather dead cases. |
| 2568 | SmallVector<ConstantInt*, 8> DeadCases; |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2569 | for (SwitchInst::CaseIt I = SI->caseBegin(), E = SI->caseEnd(); I != E; ++I) { |
| 2570 | if ((I.getCaseValue()->getValue() & KnownZero) != 0 || |
| 2571 | (I.getCaseValue()->getValue() & KnownOne) != KnownOne) { |
| 2572 | DeadCases.push_back(I.getCaseValue()); |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2573 | DEBUG(dbgs() << "SimplifyCFG: switch case '" |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2574 | << I.getCaseValue() << "' is dead.\n"); |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2575 | } |
| 2576 | } |
| 2577 | |
| 2578 | // Remove dead cases from the switch. |
| 2579 | for (unsigned I = 0, E = DeadCases.size(); I != E; ++I) { |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2580 | SwitchInst::CaseIt Case = SI->findCaseValue(DeadCases[I]); |
| 2581 | assert(Case != SI->caseDefault() && |
Stepan Dyatkovskiy | 2447312 | 2012-02-01 07:49:51 +0000 | [diff] [blame] | 2582 | "Case was not found. Probably mistake in DeadCases forming."); |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2583 | // Prune unused values from PHI nodes. |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2584 | Case.getCaseSuccessor()->removePredecessor(SI->getParent()); |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2585 | SI->removeCase(Case); |
| 2586 | } |
| 2587 | |
| 2588 | return !DeadCases.empty(); |
| 2589 | } |
| 2590 | |
Hans Wennborg | 448da51 | 2011-06-18 10:28:47 +0000 | [diff] [blame] | 2591 | /// FindPHIForConditionForwarding - If BB would be eligible for simplification |
| 2592 | /// by TryToSimplifyUncondBranchFromEmptyBlock (i.e. it is empty and terminated |
| 2593 | /// by an unconditional branch), look at the phi node for BB in the successor |
| 2594 | /// block and see if the incoming value is equal to CaseValue. If so, return |
| 2595 | /// the phi node, and set PhiIndex to BB's index in the phi node. |
| 2596 | static PHINode *FindPHIForConditionForwarding(ConstantInt *CaseValue, |
| 2597 | BasicBlock *BB, |
| 2598 | int *PhiIndex) { |
| 2599 | if (BB->getFirstNonPHIOrDbg() != BB->getTerminator()) |
| 2600 | return NULL; // BB must be empty to be a candidate for simplification. |
| 2601 | if (!BB->getSinglePredecessor()) |
| 2602 | return NULL; // BB must be dominated by the switch. |
| 2603 | |
| 2604 | BranchInst *Branch = dyn_cast<BranchInst>(BB->getTerminator()); |
| 2605 | if (!Branch || !Branch->isUnconditional()) |
| 2606 | return NULL; // Terminator must be unconditional branch. |
| 2607 | |
| 2608 | BasicBlock *Succ = Branch->getSuccessor(0); |
| 2609 | |
| 2610 | BasicBlock::iterator I = Succ->begin(); |
| 2611 | while (PHINode *PHI = dyn_cast<PHINode>(I++)) { |
| 2612 | int Idx = PHI->getBasicBlockIndex(BB); |
| 2613 | assert(Idx >= 0 && "PHI has no entry for predecessor?"); |
| 2614 | |
| 2615 | Value *InValue = PHI->getIncomingValue(Idx); |
| 2616 | if (InValue != CaseValue) continue; |
| 2617 | |
| 2618 | *PhiIndex = Idx; |
| 2619 | return PHI; |
| 2620 | } |
| 2621 | |
| 2622 | return NULL; |
| 2623 | } |
| 2624 | |
| 2625 | /// ForwardSwitchConditionToPHI - Try to forward the condition of a switch |
| 2626 | /// instruction to a phi node dominated by the switch, if that would mean that |
| 2627 | /// some of the destination blocks of the switch can be folded away. |
| 2628 | /// Returns true if a change is made. |
| 2629 | static bool ForwardSwitchConditionToPHI(SwitchInst *SI) { |
| 2630 | typedef DenseMap<PHINode*, SmallVector<int,4> > ForwardingNodesMap; |
| 2631 | ForwardingNodesMap ForwardingNodes; |
| 2632 | |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame^] | 2633 | for (SwitchInst::CaseIt I = SI->caseBegin(), E = SI->caseEnd(); I != E; ++I) { |
| 2634 | ConstantInt *CaseValue = I.getCaseValue(); |
| 2635 | BasicBlock *CaseDest = I.getCaseSuccessor(); |
Hans Wennborg | 448da51 | 2011-06-18 10:28:47 +0000 | [diff] [blame] | 2636 | |
| 2637 | int PhiIndex; |
| 2638 | PHINode *PHI = FindPHIForConditionForwarding(CaseValue, CaseDest, |
| 2639 | &PhiIndex); |
| 2640 | if (!PHI) continue; |
| 2641 | |
| 2642 | ForwardingNodes[PHI].push_back(PhiIndex); |
| 2643 | } |
| 2644 | |
| 2645 | bool Changed = false; |
| 2646 | |
| 2647 | for (ForwardingNodesMap::iterator I = ForwardingNodes.begin(), |
| 2648 | E = ForwardingNodes.end(); I != E; ++I) { |
| 2649 | PHINode *Phi = I->first; |
| 2650 | SmallVector<int,4> &Indexes = I->second; |
| 2651 | |
| 2652 | if (Indexes.size() < 2) continue; |
| 2653 | |
| 2654 | for (size_t I = 0, E = Indexes.size(); I != E; ++I) |
| 2655 | Phi->setIncomingValue(Indexes[I], SI->getCondition()); |
| 2656 | Changed = true; |
| 2657 | } |
| 2658 | |
| 2659 | return Changed; |
| 2660 | } |
| 2661 | |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2662 | bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2663 | // If this switch is too complex to want to look at, ignore it. |
| 2664 | if (!isValueEqualityComparison(SI)) |
| 2665 | return false; |
| 2666 | |
| 2667 | BasicBlock *BB = SI->getParent(); |
| 2668 | |
| 2669 | // If we only have one predecessor, and if it is a branch on this value, |
| 2670 | // see if that predecessor totally determines the outcome of this switch. |
| 2671 | if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2672 | if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder)) |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2673 | return SimplifyCFG(BB) | true; |
Frits van Bommel | f7b2a9d | 2011-02-28 09:44:07 +0000 | [diff] [blame] | 2674 | |
| 2675 | Value *Cond = SI->getCondition(); |
| 2676 | if (SelectInst *Select = dyn_cast<SelectInst>(Cond)) |
| 2677 | if (SimplifySwitchOnSelect(SI, Select)) |
| 2678 | return SimplifyCFG(BB) | true; |
| 2679 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2680 | // If the block only contains the switch, see if we can fold the block |
| 2681 | // away into any preds. |
| 2682 | BasicBlock::iterator BBI = BB->begin(); |
| 2683 | // Ignore dbg intrinsics. |
| 2684 | while (isa<DbgInfoIntrinsic>(BBI)) |
| 2685 | ++BBI; |
| 2686 | if (SI == &*BBI) |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 2687 | if (FoldValueComparisonIntoPredecessors(SI, Builder)) |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2688 | return SimplifyCFG(BB) | true; |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2689 | |
| 2690 | // Try to transform the switch into an icmp and a branch. |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2691 | if (TurnSwitchRangeIntoICmp(SI, Builder)) |
Benjamin Kramer | 56442df | 2011-02-02 15:56:22 +0000 | [diff] [blame] | 2692 | return SimplifyCFG(BB) | true; |
Benjamin Kramer | 10fcfb5 | 2011-05-14 15:57:25 +0000 | [diff] [blame] | 2693 | |
| 2694 | // Remove unreachable cases. |
| 2695 | if (EliminateDeadSwitchCases(SI)) |
| 2696 | return SimplifyCFG(BB) | true; |
| 2697 | |
Hans Wennborg | 448da51 | 2011-06-18 10:28:47 +0000 | [diff] [blame] | 2698 | if (ForwardSwitchConditionToPHI(SI)) |
| 2699 | return SimplifyCFG(BB) | true; |
| 2700 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2701 | return false; |
| 2702 | } |
| 2703 | |
| 2704 | bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { |
| 2705 | BasicBlock *BB = IBI->getParent(); |
| 2706 | bool Changed = false; |
| 2707 | |
| 2708 | // Eliminate redundant destinations. |
| 2709 | SmallPtrSet<Value *, 8> Succs; |
| 2710 | for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { |
| 2711 | BasicBlock *Dest = IBI->getDestination(i); |
| 2712 | if (!Dest->hasAddressTaken() || !Succs.insert(Dest)) { |
| 2713 | Dest->removePredecessor(BB); |
| 2714 | IBI->removeDestination(i); |
| 2715 | --i; --e; |
| 2716 | Changed = true; |
| 2717 | } |
| 2718 | } |
| 2719 | |
| 2720 | if (IBI->getNumDestinations() == 0) { |
| 2721 | // If the indirectbr has no successors, change it to unreachable. |
| 2722 | new UnreachableInst(IBI->getContext(), IBI); |
| 2723 | EraseTerminatorInstAndDCECond(IBI); |
| 2724 | return true; |
| 2725 | } |
| 2726 | |
| 2727 | if (IBI->getNumDestinations() == 1) { |
| 2728 | // If the indirectbr has one successor, change it to a direct branch. |
| 2729 | BranchInst::Create(IBI->getDestination(0), IBI); |
| 2730 | EraseTerminatorInstAndDCECond(IBI); |
| 2731 | return true; |
| 2732 | } |
| 2733 | |
| 2734 | if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) { |
| 2735 | if (SimplifyIndirectBrOnSelect(IBI, SI)) |
| 2736 | return SimplifyCFG(BB) | true; |
| 2737 | } |
| 2738 | return Changed; |
| 2739 | } |
| 2740 | |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 2741 | bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2742 | BasicBlock *BB = BI->getParent(); |
| 2743 | |
| 2744 | // If the Terminator is the only non-phi instruction, simplify the block. |
Rafael Espindola | 77a2c37 | 2011-06-30 20:14:24 +0000 | [diff] [blame] | 2745 | BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime(); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2746 | if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() && |
| 2747 | TryToSimplifyUncondBranchFromEmptyBlock(BB)) |
| 2748 | return true; |
| 2749 | |
| 2750 | // If the only instruction in the block is a seteq/setne comparison |
| 2751 | // against a constant, try to simplify the block. |
| 2752 | if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) |
| 2753 | if (ICI->isEquality() && isa<ConstantInt>(ICI->getOperand(1))) { |
| 2754 | for (++I; isa<DbgInfoIntrinsic>(I); ++I) |
| 2755 | ; |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 2756 | if (I->isTerminator() && |
| 2757 | TryToSimplifyUncondBranchWithICmpInIt(ICI, TD, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2758 | return true; |
| 2759 | } |
| 2760 | |
| 2761 | return false; |
| 2762 | } |
| 2763 | |
| 2764 | |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2765 | bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2766 | BasicBlock *BB = BI->getParent(); |
| 2767 | |
| 2768 | // Conditional branch |
| 2769 | if (isValueEqualityComparison(BI)) { |
| 2770 | // If we only have one predecessor, and if it is a branch on this value, |
| 2771 | // see if that predecessor totally determines the outcome of this |
| 2772 | // switch. |
| 2773 | if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2774 | if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2775 | return SimplifyCFG(BB) | true; |
| 2776 | |
| 2777 | // This block must be empty, except for the setcond inst, if it exists. |
| 2778 | // Ignore dbg intrinsics. |
| 2779 | BasicBlock::iterator I = BB->begin(); |
| 2780 | // Ignore dbg intrinsics. |
| 2781 | while (isa<DbgInfoIntrinsic>(I)) |
| 2782 | ++I; |
| 2783 | if (&*I == BI) { |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 2784 | if (FoldValueComparisonIntoPredecessors(BI, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2785 | return SimplifyCFG(BB) | true; |
| 2786 | } else if (&*I == cast<Instruction>(BI->getCondition())){ |
| 2787 | ++I; |
| 2788 | // Ignore dbg intrinsics. |
| 2789 | while (isa<DbgInfoIntrinsic>(I)) |
| 2790 | ++I; |
Devang Patel | b55d924 | 2011-05-18 20:53:17 +0000 | [diff] [blame] | 2791 | if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2792 | return SimplifyCFG(BB) | true; |
| 2793 | } |
| 2794 | } |
| 2795 | |
| 2796 | // Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction. |
Devang Patel | 02dd541 | 2011-05-18 23:18:47 +0000 | [diff] [blame] | 2797 | if (SimplifyBranchOnICmpChain(BI, TD, Builder)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2798 | return true; |
| 2799 | |
Dan Gohman | 3b20517 | 2012-01-05 23:58:56 +0000 | [diff] [blame] | 2800 | // If this basic block is ONLY a compare and a branch, and if a predecessor |
| 2801 | // branches to us and one of our successors, fold the comparison into the |
| 2802 | // predecessor and use logical operations to pick the right destination. |
| 2803 | if (FoldBranchToCommonDest(BI)) |
| 2804 | return SimplifyCFG(BB) | true; |
| 2805 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2806 | // We have a conditional branch to two blocks that are only reachable |
| 2807 | // from BI. We know that the condbr dominates the two blocks, so see if |
| 2808 | // there is any identical code in the "then" and "else" blocks. If so, we |
| 2809 | // can hoist it up to the branching block. |
| 2810 | if (BI->getSuccessor(0)->getSinglePredecessor() != 0) { |
| 2811 | if (BI->getSuccessor(1)->getSinglePredecessor() != 0) { |
Rafael Espindola | 216dde9 | 2011-05-19 02:26:30 +0000 | [diff] [blame] | 2812 | if (HoistThenElseCodeToIf(BI)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2813 | return SimplifyCFG(BB) | true; |
| 2814 | } else { |
| 2815 | // If Successor #1 has multiple preds, we may be able to conditionally |
| 2816 | // execute Successor #0 if it branches to successor #1. |
| 2817 | TerminatorInst *Succ0TI = BI->getSuccessor(0)->getTerminator(); |
| 2818 | if (Succ0TI->getNumSuccessors() == 1 && |
| 2819 | Succ0TI->getSuccessor(0) == BI->getSuccessor(1)) |
Rafael Espindola | 216dde9 | 2011-05-19 02:26:30 +0000 | [diff] [blame] | 2820 | if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0))) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2821 | return SimplifyCFG(BB) | true; |
| 2822 | } |
| 2823 | } else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) { |
| 2824 | // If Successor #0 has multiple preds, we may be able to conditionally |
| 2825 | // execute Successor #1 if it branches to successor #0. |
| 2826 | TerminatorInst *Succ1TI = BI->getSuccessor(1)->getTerminator(); |
| 2827 | if (Succ1TI->getNumSuccessors() == 1 && |
| 2828 | Succ1TI->getSuccessor(0) == BI->getSuccessor(0)) |
Rafael Espindola | 216dde9 | 2011-05-19 02:26:30 +0000 | [diff] [blame] | 2829 | if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1))) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2830 | return SimplifyCFG(BB) | true; |
| 2831 | } |
| 2832 | |
| 2833 | // If this is a branch on a phi node in the current block, thread control |
| 2834 | // through this block if any PHI node entries are constants. |
| 2835 | if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition())) |
| 2836 | if (PN->getParent() == BI->getParent()) |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2837 | if (FoldCondBranchOnPHI(BI, TD)) |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2838 | return SimplifyCFG(BB) | true; |
| 2839 | |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2840 | // Scan predecessor blocks for conditional branches. |
| 2841 | for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) |
| 2842 | if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) |
| 2843 | if (PBI != BI && PBI->isConditional()) |
| 2844 | if (SimplifyCondBranchToCondBranch(PBI, BI)) |
| 2845 | return SimplifyCFG(BB) | true; |
| 2846 | |
| 2847 | return false; |
| 2848 | } |
| 2849 | |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2850 | /// Check if passing a value to an instruction will cause undefined behavior. |
| 2851 | static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) { |
| 2852 | Constant *C = dyn_cast<Constant>(V); |
| 2853 | if (!C) |
| 2854 | return false; |
| 2855 | |
Benjamin Kramer | 9bb5488 | 2011-08-26 02:25:55 +0000 | [diff] [blame] | 2856 | if (!I->hasOneUse()) // Only look at single-use instructions, for compile time |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2857 | return false; |
| 2858 | |
| 2859 | if (C->isNullValue()) { |
| 2860 | Instruction *Use = I->use_back(); |
| 2861 | |
| 2862 | // Now make sure that there are no instructions in between that can alter |
| 2863 | // control flow (eg. calls) |
| 2864 | for (BasicBlock::iterator i = ++BasicBlock::iterator(I); &*i != Use; ++i) |
Benjamin Kramer | 9bb5488 | 2011-08-26 02:25:55 +0000 | [diff] [blame] | 2865 | if (i == I->getParent()->end() || i->mayHaveSideEffects()) |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2866 | return false; |
| 2867 | |
| 2868 | // Look through GEPs. A load from a GEP derived from NULL is still undefined |
| 2869 | if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Use)) |
| 2870 | if (GEP->getPointerOperand() == I) |
| 2871 | return passingValueIsAlwaysUndefined(V, GEP); |
| 2872 | |
| 2873 | // Look through bitcasts. |
| 2874 | if (BitCastInst *BC = dyn_cast<BitCastInst>(Use)) |
| 2875 | return passingValueIsAlwaysUndefined(V, BC); |
| 2876 | |
Benjamin Kramer | 9bb5488 | 2011-08-26 02:25:55 +0000 | [diff] [blame] | 2877 | // Load from null is undefined. |
| 2878 | if (LoadInst *LI = dyn_cast<LoadInst>(Use)) |
| 2879 | return LI->getPointerAddressSpace() == 0; |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2880 | |
Benjamin Kramer | 9bb5488 | 2011-08-26 02:25:55 +0000 | [diff] [blame] | 2881 | // Store to null is undefined. |
| 2882 | if (StoreInst *SI = dyn_cast<StoreInst>(Use)) |
| 2883 | return SI->getPointerAddressSpace() == 0 && SI->getPointerOperand() == I; |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2884 | } |
| 2885 | return false; |
| 2886 | } |
| 2887 | |
| 2888 | /// If BB has an incoming value that will always trigger undefined behavior |
Nick Lewycky | 9d52310 | 2011-12-26 20:37:40 +0000 | [diff] [blame] | 2889 | /// (eg. null pointer dereference), remove the branch leading here. |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2890 | static bool removeUndefIntroducingPredecessor(BasicBlock *BB) { |
| 2891 | for (BasicBlock::iterator i = BB->begin(); |
| 2892 | PHINode *PHI = dyn_cast<PHINode>(i); ++i) |
| 2893 | for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) |
| 2894 | if (passingValueIsAlwaysUndefined(PHI->getIncomingValue(i), PHI)) { |
| 2895 | TerminatorInst *T = PHI->getIncomingBlock(i)->getTerminator(); |
| 2896 | IRBuilder<> Builder(T); |
| 2897 | if (BranchInst *BI = dyn_cast<BranchInst>(T)) { |
| 2898 | BB->removePredecessor(PHI->getIncomingBlock(i)); |
| 2899 | // Turn uncoditional branches into unreachables and remove the dead |
| 2900 | // destination from conditional branches. |
| 2901 | if (BI->isUnconditional()) |
| 2902 | Builder.CreateUnreachable(); |
| 2903 | else |
| 2904 | Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1) : |
| 2905 | BI->getSuccessor(0)); |
| 2906 | BI->eraseFromParent(); |
| 2907 | return true; |
| 2908 | } |
| 2909 | // TODO: SwitchInst. |
| 2910 | } |
| 2911 | |
| 2912 | return false; |
| 2913 | } |
| 2914 | |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 2915 | bool SimplifyCFGOpt::run(BasicBlock *BB) { |
Chris Lattner | dc3602b | 2003-08-24 18:36:16 +0000 | [diff] [blame] | 2916 | bool Changed = false; |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 2917 | |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2918 | assert(BB && BB->getParent() && "Block not embedded in function!"); |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 2919 | assert(BB->getTerminator() && "Degenerate basic block encountered!"); |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 2920 | |
Dan Gohman | e2c6d13 | 2010-08-14 00:29:42 +0000 | [diff] [blame] | 2921 | // Remove basic blocks that have no predecessors (except the entry block)... |
| 2922 | // or that just have themself as a predecessor. These are unreachable. |
Chris Lattner | 302ba6f | 2010-12-14 06:17:25 +0000 | [diff] [blame] | 2923 | if ((pred_begin(BB) == pred_end(BB) && |
| 2924 | BB != &BB->getParent()->getEntryBlock()) || |
Dan Gohman | e2c6d13 | 2010-08-14 00:29:42 +0000 | [diff] [blame] | 2925 | BB->getSinglePredecessor() == BB) { |
David Greene | 89d6fd3 | 2010-01-05 01:26:52 +0000 | [diff] [blame] | 2926 | DEBUG(dbgs() << "Removing BB: \n" << *BB); |
Chris Lattner | 71af9b0 | 2008-12-03 06:40:52 +0000 | [diff] [blame] | 2927 | DeleteDeadBlock(BB); |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 2928 | return true; |
| 2929 | } |
| 2930 | |
Chris Lattner | 694e37f | 2003-08-17 19:41:53 +0000 | [diff] [blame] | 2931 | // Check to see if we can constant propagate this terminator instruction |
| 2932 | // away... |
Frits van Bommel | 5649ba7 | 2011-05-22 16:24:18 +0000 | [diff] [blame] | 2933 | Changed |= ConstantFoldTerminator(BB, true); |
Chris Lattner | 694e37f | 2003-08-17 19:41:53 +0000 | [diff] [blame] | 2934 | |
Dan Gohman | 2c63566 | 2009-10-30 22:39:04 +0000 | [diff] [blame] | 2935 | // Check for and eliminate duplicate PHI nodes in this block. |
| 2936 | Changed |= EliminateDuplicatePHINodes(BB); |
| 2937 | |
Benjamin Kramer | 98d6d23 | 2011-08-26 01:22:29 +0000 | [diff] [blame] | 2938 | // Check for and remove branches that will always cause undefined behavior. |
| 2939 | Changed |= removeUndefIntroducingPredecessor(BB); |
| 2940 | |
Chris Lattner | ddb97a2 | 2010-12-13 05:10:48 +0000 | [diff] [blame] | 2941 | // Merge basic blocks into their predecessor if there is only one distinct |
| 2942 | // pred, and if there is only one distinct successor of the predecessor, and |
| 2943 | // if there are no PHI nodes. |
| 2944 | // |
| 2945 | if (MergeBlockIntoPredecessor(BB)) |
| 2946 | return true; |
| 2947 | |
Devang Patel | 3e410c6 | 2011-05-18 18:01:27 +0000 | [diff] [blame] | 2948 | IRBuilder<> Builder(BB); |
| 2949 | |
Dan Gohman | 882d87d | 2008-03-11 21:53:06 +0000 | [diff] [blame] | 2950 | // If there is a trivial two-entry PHI node in this basic block, and we can |
| 2951 | // eliminate it, do so now. |
| 2952 | if (PHINode *PN = dyn_cast<PHINode>(BB->begin())) |
| 2953 | if (PN->getNumIncomingValues() == 2) |
Devang Patel | d3a1788 | 2011-05-19 20:52:46 +0000 | [diff] [blame] | 2954 | Changed |= FoldTwoEntryPHINode(PN, TD); |
Dan Gohman | 882d87d | 2008-03-11 21:53:06 +0000 | [diff] [blame] | 2955 | |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2956 | Builder.SetInsertPoint(BB->getTerminator()); |
Chris Lattner | 3d51213 | 2010-12-13 06:25:44 +0000 | [diff] [blame] | 2957 | if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) { |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2958 | if (BI->isUnconditional()) { |
Devang Patel | a23812c | 2011-05-18 18:28:48 +0000 | [diff] [blame] | 2959 | if (SimplifyUncondBranch(BI, Builder)) return true; |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2960 | } else { |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2961 | if (SimplifyCondBranch(BI, Builder)) return true; |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2962 | } |
| 2963 | } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { |
Devang Patel | 176ec40 | 2011-05-18 21:33:11 +0000 | [diff] [blame] | 2964 | if (SimplifyReturn(RI, Builder)) return true; |
Bill Wendling | aa5abe8 | 2012-02-06 21:16:41 +0000 | [diff] [blame] | 2965 | } else if (ResumeInst *RI = dyn_cast<ResumeInst>(BB->getTerminator())) { |
| 2966 | if (SimplifyResume(RI, Builder)) return true; |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2967 | } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) { |
Devang Patel | 007349d | 2011-05-18 20:35:38 +0000 | [diff] [blame] | 2968 | if (SimplifySwitch(SI, Builder)) return true; |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2969 | } else if (UnreachableInst *UI = |
| 2970 | dyn_cast<UnreachableInst>(BB->getTerminator())) { |
| 2971 | if (SimplifyUnreachable(UI)) return true; |
Chris Lattner | 021c9d3 | 2010-12-13 06:36:51 +0000 | [diff] [blame] | 2972 | } else if (IndirectBrInst *IBI = |
| 2973 | dyn_cast<IndirectBrInst>(BB->getTerminator())) { |
| 2974 | if (SimplifyIndirectBr(IBI)) return true; |
Chris Lattner | 19831ec | 2004-02-16 06:35:48 +0000 | [diff] [blame] | 2975 | } |
| 2976 | |
Chris Lattner | 694e37f | 2003-08-17 19:41:53 +0000 | [diff] [blame] | 2977 | return Changed; |
Chris Lattner | 01d1ee3 | 2002-05-21 20:50:24 +0000 | [diff] [blame] | 2978 | } |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 2979 | |
| 2980 | /// SimplifyCFG - This function is used to do simplification of a CFG. For |
| 2981 | /// example, it adjusts branches to branches to eliminate the extra hop, it |
| 2982 | /// eliminates unreachable basic blocks, and does other "peephole" optimization |
| 2983 | /// of the CFG. It returns true if a modification was made. |
| 2984 | /// |
Jakob Stoklund Olesen | 58e9ee8 | 2010-02-05 22:03:18 +0000 | [diff] [blame] | 2985 | bool llvm::SimplifyCFG(BasicBlock *BB, const TargetData *TD) { |
| 2986 | return SimplifyCFGOpt(TD).run(BB); |
| 2987 | } |