Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 1 | //===- LoopIndexSplit.cpp - Loop Index Splitting Pass ---------------------===// |
| 2 | // |
| 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. |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // This file implements Loop Index Splitting Pass. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
| 14 | #define DEBUG_TYPE "loop-index-split" |
| 15 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 16 | #include "llvm/Transforms/Scalar.h" |
| 17 | #include "llvm/Analysis/LoopPass.h" |
| 18 | #include "llvm/Analysis/ScalarEvolutionExpander.h" |
Devang Patel | 787a713 | 2007-08-08 21:39:47 +0000 | [diff] [blame] | 19 | #include "llvm/Analysis/Dominators.h" |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 20 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| 21 | #include "llvm/Transforms/Utils/Cloning.h" |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 22 | #include "llvm/Support/Compiler.h" |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 23 | #include "llvm/ADT/DepthFirstIterator.h" |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 24 | #include "llvm/ADT/Statistic.h" |
| 25 | |
| 26 | using namespace llvm; |
| 27 | |
| 28 | STATISTIC(NumIndexSplit, "Number of loops index split"); |
| 29 | |
| 30 | namespace { |
| 31 | |
| 32 | class VISIBILITY_HIDDEN LoopIndexSplit : public LoopPass { |
| 33 | |
| 34 | public: |
| 35 | static char ID; // Pass ID, replacement for typeid |
| 36 | LoopIndexSplit() : LoopPass((intptr_t)&ID) {} |
| 37 | |
| 38 | // Index split Loop L. Return true if loop is split. |
| 39 | bool runOnLoop(Loop *L, LPPassManager &LPM); |
| 40 | |
| 41 | void getAnalysisUsage(AnalysisUsage &AU) const { |
| 42 | AU.addRequired<ScalarEvolution>(); |
| 43 | AU.addPreserved<ScalarEvolution>(); |
| 44 | AU.addRequiredID(LCSSAID); |
| 45 | AU.addPreservedID(LCSSAID); |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 46 | AU.addRequired<LoopInfo>(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 47 | AU.addPreserved<LoopInfo>(); |
| 48 | AU.addRequiredID(LoopSimplifyID); |
| 49 | AU.addPreservedID(LoopSimplifyID); |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 50 | AU.addRequired<DominatorTree>(); |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 51 | AU.addRequired<DominanceFrontier>(); |
Devang Patel | 787a713 | 2007-08-08 21:39:47 +0000 | [diff] [blame] | 52 | AU.addPreserved<DominatorTree>(); |
| 53 | AU.addPreserved<DominanceFrontier>(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 54 | } |
| 55 | |
| 56 | private: |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 57 | |
| 58 | class SplitInfo { |
| 59 | public: |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 60 | SplitInfo() : SplitValue(NULL), SplitCondition(NULL), |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 61 | UseTrueBranchFirst(true), A_ExitValue(NULL), |
| 62 | B_StartValue(NULL) {} |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 63 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 64 | // Induction variable's range is split at this value. |
| 65 | Value *SplitValue; |
| 66 | |
Devang Patel | 4f12c5f | 2007-09-11 00:12:56 +0000 | [diff] [blame] | 67 | // This instruction compares IndVar against SplitValue. |
| 68 | Instruction *SplitCondition; |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 69 | |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 70 | // True if after loop index split, first loop will execute split condition's |
| 71 | // true branch. |
| 72 | bool UseTrueBranchFirst; |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 73 | |
| 74 | // Exit value for first loop after loop split. |
| 75 | Value *A_ExitValue; |
| 76 | |
| 77 | // Start value for second loop after loop split. |
| 78 | Value *B_StartValue; |
| 79 | |
Devang Patel | 9021c70 | 2007-08-08 21:18:27 +0000 | [diff] [blame] | 80 | // Clear split info. |
| 81 | void clear() { |
Devang Patel | 9021c70 | 2007-08-08 21:18:27 +0000 | [diff] [blame] | 82 | SplitValue = NULL; |
Devang Patel | 9021c70 | 2007-08-08 21:18:27 +0000 | [diff] [blame] | 83 | SplitCondition = NULL; |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 84 | UseTrueBranchFirst = true; |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 85 | A_ExitValue = NULL; |
| 86 | B_StartValue = NULL; |
Devang Patel | 9021c70 | 2007-08-08 21:18:27 +0000 | [diff] [blame] | 87 | } |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 88 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 89 | }; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 90 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 91 | private: |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 92 | |
| 93 | // safeIcmpInst - CI is considered safe instruction if one of the operand |
| 94 | // is SCEVAddRecExpr based on induction variable and other operand is |
| 95 | // loop invariant. If CI is safe then populate SplitInfo object SD appropriately |
| 96 | // and return true; |
| 97 | bool safeICmpInst(ICmpInst *CI, SplitInfo &SD); |
| 98 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 99 | /// Find condition inside a loop that is suitable candidate for index split. |
| 100 | void findSplitCondition(); |
| 101 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 102 | /// Find loop's exit condition. |
| 103 | void findLoopConditionals(); |
| 104 | |
| 105 | /// Return induction variable associated with value V. |
| 106 | void findIndVar(Value *V, Loop *L); |
| 107 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 108 | /// processOneIterationLoop - Current loop L contains compare instruction |
| 109 | /// that compares induction variable, IndVar, agains loop invariant. If |
| 110 | /// entire (i.e. meaningful) loop body is dominated by this compare |
| 111 | /// instruction then loop body is executed only for one iteration. In |
| 112 | /// such case eliminate loop structure surrounding this loop body. For |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 113 | bool processOneIterationLoop(SplitInfo &SD); |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 114 | |
| 115 | void updateLoopBounds(ICmpInst *CI); |
| 116 | /// updateLoopIterationSpace - Current loop body is covered by an AND |
| 117 | /// instruction whose operands compares induction variables with loop |
| 118 | /// invariants. If possible, hoist this check outside the loop by |
| 119 | /// updating appropriate start and end values for induction variable. |
| 120 | bool updateLoopIterationSpace(SplitInfo &SD); |
| 121 | |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 122 | /// If loop header includes loop variant instruction operands then |
| 123 | /// this loop may not be eliminated. |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 124 | bool safeHeader(SplitInfo &SD, BasicBlock *BB); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 125 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 126 | /// If Exiting block includes loop variant instructions then this |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 127 | /// loop may not be eliminated. |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 128 | bool safeExitingBlock(SplitInfo &SD, BasicBlock *BB); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 129 | |
Devang Patel | a6a8663 | 2007-08-14 18:35:57 +0000 | [diff] [blame] | 130 | /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB. |
| 131 | /// This routine is used to remove split condition's dead branch, dominated by |
| 132 | /// DeadBB. LiveBB dominates split conidition's other branch. |
| 133 | void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB); |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 134 | |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 135 | /// safeSplitCondition - Return true if it is possible to |
| 136 | /// split loop using given split condition. |
| 137 | bool safeSplitCondition(SplitInfo &SD); |
| 138 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 139 | /// calculateLoopBounds - ALoop exit value and BLoop start values are calculated |
| 140 | /// based on split value. |
| 141 | void calculateLoopBounds(SplitInfo &SD); |
| 142 | |
Devang Patel | d79faee | 2007-08-25 02:39:24 +0000 | [diff] [blame] | 143 | /// updatePHINodes - CFG has been changed. |
| 144 | /// Before |
| 145 | /// - ExitBB's single predecessor was Latch |
| 146 | /// - Latch's second successor was Header |
| 147 | /// Now |
| 148 | /// - ExitBB's single predecessor was Header |
| 149 | /// - Latch's one and only successor was Header |
| 150 | /// |
| 151 | /// Update ExitBB PHINodes' to reflect this change. |
| 152 | void updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, |
| 153 | BasicBlock *Header, |
| 154 | PHINode *IV, Instruction *IVIncrement); |
| 155 | |
| 156 | /// moveExitCondition - Move exit condition EC into split condition block CondBB. |
| 157 | void moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB, |
| 158 | BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC, |
| 159 | PHINode *IV, Instruction *IVAdd, Loop *LP); |
| 160 | |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 161 | /// splitLoop - Split current loop L in two loops using split information |
| 162 | /// SD. Update dominator information. Maintain LCSSA form. |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 163 | bool splitLoop(SplitInfo &SD); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 164 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 165 | void initialize() { |
| 166 | IndVar = NULL; |
| 167 | IndVarIncrement = NULL; |
| 168 | ExitCondition = NULL; |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 169 | StartValue = NULL; |
| 170 | ExitValueNum = 0; |
| 171 | SplitData.clear(); |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 172 | } |
| 173 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 174 | private: |
| 175 | |
| 176 | // Current Loop. |
| 177 | Loop *L; |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 178 | LPPassManager *LPM; |
| 179 | LoopInfo *LI; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 180 | ScalarEvolution *SE; |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 181 | DominatorTree *DT; |
Devang Patel | fc4c5f8 | 2007-08-13 22:13:24 +0000 | [diff] [blame] | 182 | DominanceFrontier *DF; |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 183 | SmallVector<SplitInfo, 4> SplitData; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 184 | |
| 185 | // Induction variable whose range is being split by this transformation. |
| 186 | PHINode *IndVar; |
| 187 | Instruction *IndVarIncrement; |
| 188 | |
| 189 | // Loop exit condition. |
| 190 | ICmpInst *ExitCondition; |
| 191 | |
| 192 | // Induction variable's initial value. |
| 193 | Value *StartValue; |
| 194 | |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 195 | // Induction variable's final loop exit value operand number in exit condition.. |
| 196 | unsigned ExitValueNum; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 197 | }; |
| 198 | |
| 199 | char LoopIndexSplit::ID = 0; |
| 200 | RegisterPass<LoopIndexSplit> X ("loop-index-split", "Index Split Loops"); |
| 201 | } |
| 202 | |
| 203 | LoopPass *llvm::createLoopIndexSplitPass() { |
| 204 | return new LoopIndexSplit(); |
| 205 | } |
| 206 | |
| 207 | // Index split Loop L. Return true if loop is split. |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 208 | bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) { |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 209 | bool Changed = false; |
| 210 | L = IncomingLoop; |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 211 | LPM = &LPM_Ref; |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 212 | |
Devang Patel | 3fe4f21 | 2007-08-15 02:14:55 +0000 | [diff] [blame] | 213 | // FIXME - Nested loops make dominator info updates tricky. |
Devang Patel | 4e8061c | 2007-08-14 23:53:57 +0000 | [diff] [blame] | 214 | if (!L->getSubLoops().empty()) |
| 215 | return false; |
| 216 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 217 | SE = &getAnalysis<ScalarEvolution>(); |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 218 | DT = &getAnalysis<DominatorTree>(); |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 219 | LI = &getAnalysis<LoopInfo>(); |
Devang Patel | 7375bb9 | 2007-08-15 03:34:53 +0000 | [diff] [blame] | 220 | DF = &getAnalysis<DominanceFrontier>(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 221 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 222 | initialize(); |
| 223 | |
| 224 | findLoopConditionals(); |
| 225 | |
| 226 | if (!ExitCondition) |
| 227 | return false; |
| 228 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 229 | findSplitCondition(); |
| 230 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 231 | if (SplitData.empty()) |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 232 | return false; |
| 233 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 234 | // First see if it is possible to eliminate loop itself or not. |
| 235 | for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(), |
Devang Patel | d651f65 | 2007-08-20 20:24:15 +0000 | [diff] [blame] | 236 | E = SplitData.end(); SI != E;) { |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 237 | SplitInfo &SD = *SI; |
Devang Patel | 4f12c5f | 2007-09-11 00:12:56 +0000 | [diff] [blame] | 238 | ICmpInst *CI = dyn_cast<ICmpInst>(SD.SplitCondition); |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 239 | if (SD.SplitCondition->getOpcode() == Instruction::And) { |
| 240 | Changed = updateLoopIterationSpace(SD); |
| 241 | if (Changed) { |
| 242 | ++NumIndexSplit; |
| 243 | // If is loop is eliminated then nothing else to do here. |
| 244 | return Changed; |
| 245 | } else { |
| 246 | SmallVector<SplitInfo, 4>::iterator Delete_SI = SI; |
| 247 | ++SI; |
| 248 | SplitData.erase(Delete_SI); |
| 249 | } |
| 250 | } |
| 251 | else if (CI && CI->getPredicate() == ICmpInst::ICMP_EQ) { |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 252 | Changed = processOneIterationLoop(SD); |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 253 | if (Changed) { |
| 254 | ++NumIndexSplit; |
| 255 | // If is loop is eliminated then nothing else to do here. |
| 256 | return Changed; |
Devang Patel | d651f65 | 2007-08-20 20:24:15 +0000 | [diff] [blame] | 257 | } else { |
| 258 | SmallVector<SplitInfo, 4>::iterator Delete_SI = SI; |
| 259 | ++SI; |
| 260 | SplitData.erase(Delete_SI); |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 261 | } |
Devang Patel | d651f65 | 2007-08-20 20:24:15 +0000 | [diff] [blame] | 262 | } else |
| 263 | ++SI; |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 264 | } |
| 265 | |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 266 | if (SplitData.empty()) |
| 267 | return false; |
| 268 | |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 269 | // Split most profitiable condition. |
Devang Patel | 7237d11 | 2007-08-24 05:21:13 +0000 | [diff] [blame] | 270 | // FIXME : Implement cost analysis. |
| 271 | unsigned MostProfitableSDIndex = 0; |
| 272 | Changed = splitLoop(SplitData[MostProfitableSDIndex]); |
Devang Patel | 9704fcf | 2007-08-08 22:25:28 +0000 | [diff] [blame] | 273 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 274 | if (Changed) |
| 275 | ++NumIndexSplit; |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 276 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 277 | return Changed; |
| 278 | } |
| 279 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 280 | /// Return true if V is a induction variable or induction variable's |
| 281 | /// increment for loop L. |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 282 | void LoopIndexSplit::findIndVar(Value *V, Loop *L) { |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 283 | |
| 284 | Instruction *I = dyn_cast<Instruction>(V); |
| 285 | if (!I) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 286 | return; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 287 | |
| 288 | // Check if I is a phi node from loop header or not. |
| 289 | if (PHINode *PN = dyn_cast<PHINode>(V)) { |
| 290 | if (PN->getParent() == L->getHeader()) { |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 291 | IndVar = PN; |
| 292 | return; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 293 | } |
| 294 | } |
| 295 | |
| 296 | // Check if I is a add instruction whose one operand is |
| 297 | // phi node from loop header and second operand is constant. |
| 298 | if (I->getOpcode() != Instruction::Add) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 299 | return; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 300 | |
| 301 | Value *Op0 = I->getOperand(0); |
| 302 | Value *Op1 = I->getOperand(1); |
| 303 | |
| 304 | if (PHINode *PN = dyn_cast<PHINode>(Op0)) { |
| 305 | if (PN->getParent() == L->getHeader() |
| 306 | && isa<ConstantInt>(Op1)) { |
| 307 | IndVar = PN; |
| 308 | IndVarIncrement = I; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 309 | return; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 310 | } |
| 311 | } |
| 312 | |
| 313 | if (PHINode *PN = dyn_cast<PHINode>(Op1)) { |
| 314 | if (PN->getParent() == L->getHeader() |
| 315 | && isa<ConstantInt>(Op0)) { |
| 316 | IndVar = PN; |
| 317 | IndVarIncrement = I; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 318 | return; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 319 | } |
| 320 | } |
| 321 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 322 | return; |
| 323 | } |
| 324 | |
| 325 | // Find loop's exit condition and associated induction variable. |
| 326 | void LoopIndexSplit::findLoopConditionals() { |
| 327 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 328 | BasicBlock *ExitingBlock = NULL; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 329 | |
| 330 | for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| 331 | I != E; ++I) { |
| 332 | BasicBlock *BB = *I; |
| 333 | if (!L->isLoopExit(BB)) |
| 334 | continue; |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 335 | if (ExitingBlock) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 336 | return; |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 337 | ExitingBlock = BB; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 338 | } |
| 339 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 340 | if (!ExitingBlock) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 341 | return; |
Devang Patel | b88e420 | 2007-08-24 05:36:56 +0000 | [diff] [blame] | 342 | |
| 343 | // If exiting block is neither loop header nor loop latch then this loop is |
| 344 | // not suitable. |
| 345 | if (ExitingBlock != L->getHeader() && ExitingBlock != L->getLoopLatch()) |
| 346 | return; |
| 347 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 348 | // If exit block's terminator is conditional branch inst then we have found |
| 349 | // exit condition. |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 350 | BranchInst *BR = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 351 | if (!BR || BR->isUnconditional()) |
| 352 | return; |
| 353 | |
| 354 | ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition()); |
| 355 | if (!CI) |
| 356 | return; |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 357 | |
Bill Wendling | c684910 | 2007-09-14 01:13:55 +0000 | [diff] [blame] | 358 | // FIXME |
Devang Patel | babbe27 | 2007-09-19 00:28:47 +0000 | [diff] [blame] | 359 | if (CI->getPredicate() == ICmpInst::ICMP_EQ |
Bill Wendling | c684910 | 2007-09-14 01:13:55 +0000 | [diff] [blame] | 360 | || CI->getPredicate() == ICmpInst::ICMP_NE) |
| 361 | return; |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 362 | |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 363 | ExitCondition = CI; |
| 364 | |
| 365 | // Exit condition's one operand is loop invariant exit value and second |
| 366 | // operand is SCEVAddRecExpr based on induction variable. |
| 367 | Value *V0 = CI->getOperand(0); |
| 368 | Value *V1 = CI->getOperand(1); |
| 369 | |
| 370 | SCEVHandle SH0 = SE->getSCEV(V0); |
| 371 | SCEVHandle SH1 = SE->getSCEV(V1); |
| 372 | |
| 373 | if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) { |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 374 | ExitValueNum = 0; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 375 | findIndVar(V1, L); |
| 376 | } |
| 377 | else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) { |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 378 | ExitValueNum = 1; |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 379 | findIndVar(V0, L); |
| 380 | } |
| 381 | |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 382 | if (!IndVar) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 383 | ExitCondition = NULL; |
| 384 | else if (IndVar) { |
| 385 | BasicBlock *Preheader = L->getLoopPreheader(); |
| 386 | StartValue = IndVar->getIncomingValueForBlock(Preheader); |
| 387 | } |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 388 | } |
| 389 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 390 | /// Find condition inside a loop that is suitable candidate for index split. |
| 391 | void LoopIndexSplit::findSplitCondition() { |
| 392 | |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 393 | SplitInfo SD; |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 394 | // Check all basic block's terminators. |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 395 | for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| 396 | I != E; ++I) { |
Devang Patel | 964be45 | 2007-09-11 00:23:56 +0000 | [diff] [blame] | 397 | SD.clear(); |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 398 | BasicBlock *BB = *I; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 399 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 400 | // If this basic block does not terminate in a conditional branch |
| 401 | // then terminator is not a suitable split condition. |
| 402 | BranchInst *BR = dyn_cast<BranchInst>(BB->getTerminator()); |
| 403 | if (!BR) |
| 404 | continue; |
| 405 | |
| 406 | if (BR->isUnconditional()) |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 407 | continue; |
| 408 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 409 | if (Instruction *AndI = dyn_cast<Instruction>(BR->getCondition())) { |
| 410 | if (AndI->getOpcode() == Instruction::And) { |
| 411 | ICmpInst *Op0 = dyn_cast<ICmpInst>(AndI->getOperand(0)); |
| 412 | ICmpInst *Op1 = dyn_cast<ICmpInst>(AndI->getOperand(1)); |
| 413 | |
| 414 | if (!Op0 || !Op1) |
| 415 | continue; |
| 416 | |
| 417 | if (!safeICmpInst(Op0, SD)) |
| 418 | continue; |
| 419 | SD.clear(); |
| 420 | if (!safeICmpInst(Op1, SD)) |
| 421 | continue; |
| 422 | SD.clear(); |
| 423 | SD.SplitCondition = AndI; |
| 424 | SplitData.push_back(SD); |
| 425 | continue; |
| 426 | } |
| 427 | } |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 428 | ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition()); |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 429 | if (!CI || CI == ExitCondition) |
Devang Patel | ba32a5f | 2007-09-10 23:57:58 +0000 | [diff] [blame] | 430 | continue; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 431 | |
Devang Patel | c830aee | 2007-08-24 06:02:25 +0000 | [diff] [blame] | 432 | if (CI->getPredicate() == ICmpInst::ICMP_NE) |
Devang Patel | ba32a5f | 2007-09-10 23:57:58 +0000 | [diff] [blame] | 433 | continue; |
Devang Patel | c830aee | 2007-08-24 06:02:25 +0000 | [diff] [blame] | 434 | |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 435 | // If split condition predicate is GT or GE then first execute |
| 436 | // false branch of split condition. |
Devang Patel | c3957d1 | 2007-09-11 01:10:45 +0000 | [diff] [blame] | 437 | if (CI->getPredicate() == ICmpInst::ICMP_UGT |
| 438 | || CI->getPredicate() == ICmpInst::ICMP_SGT |
| 439 | || CI->getPredicate() == ICmpInst::ICMP_UGE |
| 440 | || CI->getPredicate() == ICmpInst::ICMP_SGE) |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 441 | SD.UseTrueBranchFirst = false; |
| 442 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 443 | // If one operand is loop invariant and second operand is SCEVAddRecExpr |
| 444 | // based on induction variable then CI is a candidate split condition. |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 445 | if (safeICmpInst(CI, SD)) |
| 446 | SplitData.push_back(SD); |
| 447 | } |
| 448 | } |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 449 | |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 450 | // safeIcmpInst - CI is considered safe instruction if one of the operand |
| 451 | // is SCEVAddRecExpr based on induction variable and other operand is |
| 452 | // loop invariant. If CI is safe then populate SplitInfo object SD appropriately |
| 453 | // and return true; |
| 454 | bool LoopIndexSplit::safeICmpInst(ICmpInst *CI, SplitInfo &SD) { |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 455 | |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 456 | Value *V0 = CI->getOperand(0); |
| 457 | Value *V1 = CI->getOperand(1); |
| 458 | |
| 459 | SCEVHandle SH0 = SE->getSCEV(V0); |
| 460 | SCEVHandle SH1 = SE->getSCEV(V1); |
| 461 | |
| 462 | if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) { |
| 463 | SD.SplitValue = V0; |
| 464 | SD.SplitCondition = CI; |
| 465 | if (PHINode *PN = dyn_cast<PHINode>(V1)) { |
| 466 | if (PN == IndVar) |
| 467 | return true; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 468 | } |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 469 | else if (Instruction *Insn = dyn_cast<Instruction>(V1)) { |
| 470 | if (IndVarIncrement && IndVarIncrement == Insn) |
| 471 | return true; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 472 | } |
| 473 | } |
Devang Patel | d35ed2c | 2007-09-11 00:42:56 +0000 | [diff] [blame] | 474 | else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) { |
| 475 | SD.SplitValue = V1; |
| 476 | SD.SplitCondition = CI; |
| 477 | if (PHINode *PN = dyn_cast<PHINode>(V0)) { |
| 478 | if (PN == IndVar) |
| 479 | return true; |
| 480 | } |
| 481 | else if (Instruction *Insn = dyn_cast<Instruction>(V0)) { |
| 482 | if (IndVarIncrement && IndVarIncrement == Insn) |
| 483 | return true; |
| 484 | } |
| 485 | } |
| 486 | |
| 487 | return false; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 488 | } |
| 489 | |
| 490 | /// processOneIterationLoop - Current loop L contains compare instruction |
| 491 | /// that compares induction variable, IndVar, against loop invariant. If |
| 492 | /// entire (i.e. meaningful) loop body is dominated by this compare |
| 493 | /// instruction then loop body is executed only once. In such case eliminate |
| 494 | /// loop structure surrounding this loop body. For example, |
| 495 | /// for (int i = start; i < end; ++i) { |
| 496 | /// if ( i == somevalue) { |
| 497 | /// loop_body |
| 498 | /// } |
| 499 | /// } |
| 500 | /// can be transformed into |
| 501 | /// if (somevalue >= start && somevalue < end) { |
| 502 | /// i = somevalue; |
| 503 | /// loop_body |
| 504 | /// } |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 505 | bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) { |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 506 | |
| 507 | BasicBlock *Header = L->getHeader(); |
| 508 | |
| 509 | // First of all, check if SplitCondition dominates entire loop body |
| 510 | // or not. |
| 511 | |
| 512 | // If SplitCondition is not in loop header then this loop is not suitable |
| 513 | // for this transformation. |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 514 | if (SD.SplitCondition->getParent() != Header) |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 515 | return false; |
| 516 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 517 | // If loop header includes loop variant instruction operands then |
| 518 | // this loop may not be eliminated. |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 519 | if (!safeHeader(SD, Header)) |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 520 | return false; |
| 521 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 522 | // If Exiting block includes loop variant instructions then this |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 523 | // loop may not be eliminated. |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 524 | if (!safeExitingBlock(SD, ExitCondition->getParent())) |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 525 | return false; |
| 526 | |
Devang Patel | 968eee2 | 2007-09-19 00:15:16 +0000 | [diff] [blame] | 527 | // Filter loops where split condition's false branch is not empty. |
| 528 | if (ExitCondition->getParent() != Header->getTerminator()->getSuccessor(1)) |
| 529 | return false; |
| 530 | |
Devang Patel | 8893ca6 | 2007-09-17 21:01:05 +0000 | [diff] [blame] | 531 | // If split condition is not safe then do not process this loop. |
| 532 | // For example, |
| 533 | // for(int i = 0; i < N; i++) { |
| 534 | // if ( i == XYZ) { |
| 535 | // A; |
| 536 | // else |
| 537 | // B; |
| 538 | // } |
| 539 | // C; |
| 540 | // D; |
| 541 | // } |
| 542 | if (!safeSplitCondition(SD)) |
| 543 | return false; |
| 544 | |
Devang Patel | 84ef08b | 2007-09-19 00:11:01 +0000 | [diff] [blame] | 545 | BasicBlock *Latch = L->getLoopLatch(); |
| 546 | BranchInst *BR = dyn_cast<BranchInst>(Latch->getTerminator()); |
| 547 | if (!BR) |
| 548 | return false; |
| 549 | |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 550 | // Update CFG. |
| 551 | |
Devang Patel | ebc5fea | 2007-08-20 20:49:01 +0000 | [diff] [blame] | 552 | // Replace index variable with split value in loop body. Loop body is executed |
| 553 | // only when index variable is equal to split value. |
| 554 | IndVar->replaceAllUsesWith(SD.SplitValue); |
| 555 | |
| 556 | // Remove Latch to Header edge. |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 557 | BasicBlock *LatchSucc = NULL; |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 558 | Header->removePredecessor(Latch); |
| 559 | for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch); |
| 560 | SI != E; ++SI) { |
| 561 | if (Header != *SI) |
| 562 | LatchSucc = *SI; |
| 563 | } |
| 564 | BR->setUnconditionalDest(LatchSucc); |
| 565 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 566 | Instruction *Terminator = Header->getTerminator(); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 567 | Value *ExitValue = ExitCondition->getOperand(ExitValueNum); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 568 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 569 | // Replace split condition in header. |
| 570 | // Transform |
| 571 | // SplitCondition : icmp eq i32 IndVar, SplitValue |
| 572 | // into |
| 573 | // c1 = icmp uge i32 SplitValue, StartValue |
Devang Patel | ba32a5f | 2007-09-10 23:57:58 +0000 | [diff] [blame] | 574 | // c2 = icmp ult i32 SplitValue, ExitValue |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 575 | // and i32 c1, c2 |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 576 | bool SignedPredicate = ExitCondition->isSignedPredicate(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 577 | Instruction *C1 = new ICmpInst(SignedPredicate ? |
| 578 | ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE, |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 579 | SD.SplitValue, StartValue, "lisplit", |
| 580 | Terminator); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 581 | Instruction *C2 = new ICmpInst(SignedPredicate ? |
| 582 | ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 583 | SD.SplitValue, ExitValue, "lisplit", |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 584 | Terminator); |
| 585 | Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit", |
| 586 | Terminator); |
| 587 | SD.SplitCondition->replaceAllUsesWith(NSplitCond); |
| 588 | SD.SplitCondition->eraseFromParent(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 589 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 590 | // Now, clear latch block. Remove instructions that are responsible |
| 591 | // to increment induction variable. |
| 592 | Instruction *LTerminator = Latch->getTerminator(); |
| 593 | for (BasicBlock::iterator LB = Latch->begin(), LE = Latch->end(); |
| 594 | LB != LE; ) { |
| 595 | Instruction *I = LB; |
| 596 | ++LB; |
| 597 | if (isa<PHINode>(I) || I == LTerminator) |
| 598 | continue; |
| 599 | |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 600 | if (I == IndVarIncrement) |
| 601 | I->replaceAllUsesWith(ExitValue); |
| 602 | else |
| 603 | I->replaceAllUsesWith(UndefValue::get(I->getType())); |
Devang Patel | 8431a1c | 2007-08-07 17:45:35 +0000 | [diff] [blame] | 604 | I->eraseFromParent(); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 605 | } |
| 606 | |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 607 | LPM->deleteLoopFromQueue(L); |
Devang Patel | 787a713 | 2007-08-08 21:39:47 +0000 | [diff] [blame] | 608 | |
| 609 | // Update Dominator Info. |
| 610 | // Only CFG change done is to remove Latch to Header edge. This |
| 611 | // does not change dominator tree because Latch did not dominate |
| 612 | // Header. |
Devang Patel | fc4c5f8 | 2007-08-13 22:13:24 +0000 | [diff] [blame] | 613 | if (DF) { |
Devang Patel | 787a713 | 2007-08-08 21:39:47 +0000 | [diff] [blame] | 614 | DominanceFrontier::iterator HeaderDF = DF->find(Header); |
| 615 | if (HeaderDF != DF->end()) |
| 616 | DF->removeFromFrontier(HeaderDF, Header); |
| 617 | |
| 618 | DominanceFrontier::iterator LatchDF = DF->find(Latch); |
| 619 | if (LatchDF != DF->end()) |
| 620 | DF->removeFromFrontier(LatchDF, Header); |
| 621 | } |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 622 | return true; |
| 623 | } |
| 624 | |
| 625 | // If loop header includes loop variant instruction operands then |
| 626 | // this loop can not be eliminated. This is used by processOneIterationLoop(). |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 627 | bool LoopIndexSplit::safeHeader(SplitInfo &SD, BasicBlock *Header) { |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 628 | |
| 629 | Instruction *Terminator = Header->getTerminator(); |
| 630 | for(BasicBlock::iterator BI = Header->begin(), BE = Header->end(); |
| 631 | BI != BE; ++BI) { |
| 632 | Instruction *I = BI; |
| 633 | |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 634 | // PHI Nodes are OK. |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 635 | if (isa<PHINode>(I)) |
| 636 | continue; |
| 637 | |
| 638 | // SplitCondition itself is OK. |
Devang Patel | 71554b8 | 2007-08-08 21:02:17 +0000 | [diff] [blame] | 639 | if (I == SD.SplitCondition) |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 640 | continue; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 641 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 642 | // Induction variable is OK. |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 643 | if (I == IndVar) |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 644 | continue; |
| 645 | |
| 646 | // Induction variable increment is OK. |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 647 | if (I == IndVarIncrement) |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 648 | continue; |
| 649 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 650 | // Terminator is also harmless. |
| 651 | if (I == Terminator) |
| 652 | continue; |
| 653 | |
| 654 | // Otherwise we have a instruction that may not be safe. |
| 655 | return false; |
| 656 | } |
| 657 | |
| 658 | return true; |
| 659 | } |
| 660 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 661 | // If Exiting block includes loop variant instructions then this |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 662 | // loop may not be eliminated. This is used by processOneIterationLoop(). |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 663 | bool LoopIndexSplit::safeExitingBlock(SplitInfo &SD, |
| 664 | BasicBlock *ExitingBlock) { |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 665 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 666 | for (BasicBlock::iterator BI = ExitingBlock->begin(), |
| 667 | BE = ExitingBlock->end(); BI != BE; ++BI) { |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 668 | Instruction *I = BI; |
| 669 | |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 670 | // PHI Nodes are OK. |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 671 | if (isa<PHINode>(I)) |
| 672 | continue; |
| 673 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 674 | // Induction variable increment is OK. |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 675 | if (IndVarIncrement && IndVarIncrement == I) |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 676 | continue; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 677 | |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 678 | // Check if I is induction variable increment instruction. |
Devang Patel | a6dff2f | 2007-09-25 18:24:48 +0000 | [diff] [blame] | 679 | if (I->getOpcode() == Instruction::Add) { |
Devang Patel | c9d123d | 2007-08-09 01:39:01 +0000 | [diff] [blame] | 680 | |
| 681 | Value *Op0 = I->getOperand(0); |
| 682 | Value *Op1 = I->getOperand(1); |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 683 | PHINode *PN = NULL; |
| 684 | ConstantInt *CI = NULL; |
| 685 | |
| 686 | if ((PN = dyn_cast<PHINode>(Op0))) { |
| 687 | if ((CI = dyn_cast<ConstantInt>(Op1))) |
Devang Patel | a6dff2f | 2007-09-25 18:24:48 +0000 | [diff] [blame] | 688 | if (CI->isOne()) { |
| 689 | if (!IndVarIncrement && PN == IndVar) |
| 690 | IndVarIncrement = I; |
| 691 | // else this is another loop induction variable |
| 692 | continue; |
| 693 | } |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 694 | } else |
| 695 | if ((PN = dyn_cast<PHINode>(Op1))) { |
| 696 | if ((CI = dyn_cast<ConstantInt>(Op0))) |
Devang Patel | a6dff2f | 2007-09-25 18:24:48 +0000 | [diff] [blame] | 697 | if (CI->isOne()) { |
| 698 | if (!IndVarIncrement && PN == IndVar) |
| 699 | IndVarIncrement = I; |
| 700 | // else this is another loop induction variable |
| 701 | continue; |
| 702 | } |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 703 | } |
Devang Patel | a6dff2f | 2007-09-25 18:24:48 +0000 | [diff] [blame] | 704 | } |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 705 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 706 | // I is an Exit condition if next instruction is block terminator. |
| 707 | // Exit condition is OK if it compares loop invariant exit value, |
| 708 | // which is checked below. |
Devang Patel | 002fe25 | 2007-08-07 23:17:52 +0000 | [diff] [blame] | 709 | else if (ICmpInst *EC = dyn_cast<ICmpInst>(I)) { |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 710 | if (EC == ExitCondition) |
Devang Patel | 6a2bfda | 2007-08-08 01:51:27 +0000 | [diff] [blame] | 711 | continue; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 712 | } |
| 713 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 714 | if (I == ExitingBlock->getTerminator()) |
Devang Patel | bacf519 | 2007-08-10 00:33:50 +0000 | [diff] [blame] | 715 | continue; |
| 716 | |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 717 | // Otherwise we have instruction that may not be safe. |
| 718 | return false; |
| 719 | } |
| 720 | |
Devang Patel | 1cc2ec8 | 2007-08-20 23:51:18 +0000 | [diff] [blame] | 721 | // We could not find any reason to consider ExitingBlock unsafe. |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 722 | return true; |
| 723 | } |
| 724 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 725 | void LoopIndexSplit::updateLoopBounds(ICmpInst *CI) { |
| 726 | |
| 727 | Value *V0 = CI->getOperand(0); |
| 728 | Value *V1 = CI->getOperand(1); |
| 729 | Value *NV = NULL; |
| 730 | |
| 731 | SCEVHandle SH0 = SE->getSCEV(V0); |
| 732 | |
| 733 | if (SH0->isLoopInvariant(L)) |
| 734 | NV = V0; |
| 735 | else |
| 736 | NV = V1; |
| 737 | |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 738 | if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT |
| 739 | || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT |
| 740 | || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE |
| 741 | || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) { |
| 742 | ExitCondition->swapOperands(); |
| 743 | if (ExitValueNum) |
| 744 | ExitValueNum = 0; |
| 745 | else |
| 746 | ExitValueNum = 1; |
| 747 | } |
| 748 | |
| 749 | Value *NUB = NULL; |
| 750 | Value *NLB = NULL; |
| 751 | Value *UB = ExitCondition->getOperand(ExitValueNum); |
| 752 | const Type *Ty = NV->getType(); |
| 753 | bool Sign = ExitCondition->isSignedPredicate(); |
| 754 | BasicBlock *Preheader = L->getLoopPreheader(); |
| 755 | Instruction *PHTerminator = Preheader->getTerminator(); |
| 756 | |
| 757 | assert (NV && "Unexpected value"); |
| 758 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 759 | switch (CI->getPredicate()) { |
| 760 | case ICmpInst::ICMP_ULE: |
| 761 | case ICmpInst::ICMP_SLE: |
| 762 | // for (i = LB; i < UB; ++i) |
| 763 | // if (i <= NV && ...) |
| 764 | // LOOP_BODY |
| 765 | // |
| 766 | // is transformed into |
| 767 | // NUB = min (NV+1, UB) |
| 768 | // for (i = LB; i < NUB ; ++i) |
| 769 | // LOOP_BODY |
| 770 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 771 | if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT |
| 772 | || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) { |
| 773 | Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign), |
| 774 | "lsplit.add", PHTerminator); |
| 775 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 776 | A, UB,"lsplit,c", PHTerminator); |
| 777 | NUB = new SelectInst (C, A, UB, "lsplit.nub", PHTerminator); |
| 778 | } |
| 779 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 780 | // for (i = LB; i <= UB; ++i) |
| 781 | // if (i <= NV && ...) |
| 782 | // LOOP_BODY |
| 783 | // |
| 784 | // is transformed into |
| 785 | // NUB = min (NV, UB) |
| 786 | // for (i = LB; i <= NUB ; ++i) |
| 787 | // LOOP_BODY |
| 788 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 789 | else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE |
| 790 | || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) { |
| 791 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 792 | NV, UB, "lsplit.c", PHTerminator); |
| 793 | NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator); |
| 794 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 795 | break; |
| 796 | case ICmpInst::ICMP_ULT: |
| 797 | case ICmpInst::ICMP_SLT: |
| 798 | // for (i = LB; i < UB; ++i) |
| 799 | // if (i < NV && ...) |
| 800 | // LOOP_BODY |
| 801 | // |
| 802 | // is transformed into |
| 803 | // NUB = min (NV, UB) |
| 804 | // for (i = LB; i < NUB ; ++i) |
| 805 | // LOOP_BODY |
| 806 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 807 | if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLT |
| 808 | || ExitCondition->getPredicate() == ICmpInst::ICMP_ULT) { |
| 809 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 810 | NV, UB, "lsplit.c", PHTerminator); |
| 811 | NUB = new SelectInst (C, NV, UB, "lsplit.nub", PHTerminator); |
| 812 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 813 | |
| 814 | // for (i = LB; i <= UB; ++i) |
| 815 | // if (i < NV && ...) |
| 816 | // LOOP_BODY |
| 817 | // |
| 818 | // is transformed into |
| 819 | // NUB = min (NV -1 , UB) |
| 820 | // for (i = LB; i <= NUB ; ++i) |
| 821 | // LOOP_BODY |
| 822 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 823 | else if (ExitCondition->getPredicate() == ICmpInst::ICMP_SLE |
| 824 | || ExitCondition->getPredicate() == ICmpInst::ICMP_ULE) { |
| 825 | Value *S = BinaryOperator::createSub(NV, ConstantInt::get(Ty, 1, Sign), |
| 826 | "lsplit.add", PHTerminator); |
| 827 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 828 | S, UB, "lsplit.c", PHTerminator); |
| 829 | NUB = new SelectInst (C, S, UB, "lsplit.nub", PHTerminator); |
| 830 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 831 | break; |
| 832 | case ICmpInst::ICMP_UGE: |
| 833 | case ICmpInst::ICMP_SGE: |
| 834 | // for (i = LB; i (< or <=) UB; ++i) |
| 835 | // if (i >= NV && ...) |
| 836 | // LOOP_BODY |
| 837 | // |
| 838 | // is transformed into |
| 839 | // NLB = max (NV, LB) |
| 840 | // for (i = NLB; i (< or <=) UB ; ++i) |
| 841 | // LOOP_BODY |
| 842 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 843 | { |
| 844 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 845 | NV, StartValue, "lsplit.c", PHTerminator); |
| 846 | NLB = new SelectInst (C, StartValue, NV, "lsplit.nlb", PHTerminator); |
| 847 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 848 | break; |
| 849 | case ICmpInst::ICMP_UGT: |
| 850 | case ICmpInst::ICMP_SGT: |
| 851 | // for (i = LB; i (< or <=) UB; ++i) |
| 852 | // if (i > NV && ...) |
| 853 | // LOOP_BODY |
| 854 | // |
| 855 | // is transformed into |
| 856 | // NLB = max (NV+1, LB) |
| 857 | // for (i = NLB; i (< or <=) UB ; ++i) |
| 858 | // LOOP_BODY |
| 859 | // |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 860 | { |
| 861 | Value *A = BinaryOperator::createAdd(NV, ConstantInt::get(Ty, 1, Sign), |
| 862 | "lsplit.add", PHTerminator); |
| 863 | Value *C = new ICmpInst(Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 864 | A, StartValue, "lsplit.c", PHTerminator); |
| 865 | NLB = new SelectInst (C, StartValue, A, "lsplit.nlb", PHTerminator); |
| 866 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 867 | break; |
| 868 | default: |
| 869 | assert ( 0 && "Unexpected split condition predicate"); |
| 870 | } |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 871 | |
| 872 | if (NLB) { |
| 873 | unsigned i = IndVar->getBasicBlockIndex(Preheader); |
| 874 | IndVar->setIncomingValue(i, NLB); |
| 875 | } |
| 876 | |
| 877 | if (NUB) { |
| 878 | ExitCondition->setOperand(ExitValueNum, NUB); |
| 879 | } |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 880 | } |
| 881 | /// updateLoopIterationSpace - Current loop body is covered by an AND |
| 882 | /// instruction whose operands compares induction variables with loop |
| 883 | /// invariants. If possible, hoist this check outside the loop by |
| 884 | /// updating appropriate start and end values for induction variable. |
| 885 | bool LoopIndexSplit::updateLoopIterationSpace(SplitInfo &SD) { |
| 886 | BasicBlock *Header = L->getHeader(); |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 887 | BasicBlock *ExitingBlock = ExitCondition->getParent(); |
| 888 | BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
| 889 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 890 | ICmpInst *Op0 = cast<ICmpInst>(SD.SplitCondition->getOperand(0)); |
| 891 | ICmpInst *Op1 = cast<ICmpInst>(SD.SplitCondition->getOperand(1)); |
| 892 | |
| 893 | if (Op0->getPredicate() == ICmpInst::ICMP_EQ |
| 894 | || Op0->getPredicate() == ICmpInst::ICMP_NE |
| 895 | || Op0->getPredicate() == ICmpInst::ICMP_EQ |
| 896 | || Op0->getPredicate() == ICmpInst::ICMP_NE) |
| 897 | return false; |
| 898 | |
| 899 | // Check if SplitCondition dominates entire loop body |
| 900 | // or not. |
| 901 | |
| 902 | // If SplitCondition is not in loop header then this loop is not suitable |
| 903 | // for this transformation. |
| 904 | if (SD.SplitCondition->getParent() != Header) |
| 905 | return false; |
| 906 | |
| 907 | // If loop header includes loop variant instruction operands then |
| 908 | // this loop may not be eliminated. |
| 909 | Instruction *Terminator = Header->getTerminator(); |
| 910 | for(BasicBlock::iterator BI = Header->begin(), BE = Header->end(); |
| 911 | BI != BE; ++BI) { |
| 912 | Instruction *I = BI; |
| 913 | |
| 914 | // PHI Nodes are OK. |
| 915 | if (isa<PHINode>(I)) |
| 916 | continue; |
| 917 | |
| 918 | // SplitCondition itself is OK. |
| 919 | if (I == SD.SplitCondition) |
| 920 | continue; |
| 921 | if (I == Op0 || I == Op1) |
| 922 | continue; |
| 923 | |
| 924 | // Induction variable is OK. |
| 925 | if (I == IndVar) |
| 926 | continue; |
| 927 | |
| 928 | // Induction variable increment is OK. |
| 929 | if (I == IndVarIncrement) |
| 930 | continue; |
| 931 | |
| 932 | // Terminator is also harmless. |
| 933 | if (I == Terminator) |
| 934 | continue; |
| 935 | |
| 936 | // Otherwise we have a instruction that may not be safe. |
| 937 | return false; |
| 938 | } |
| 939 | |
| 940 | // If Exiting block includes loop variant instructions then this |
| 941 | // loop may not be eliminated. |
| 942 | if (!safeExitingBlock(SD, ExitCondition->getParent())) |
| 943 | return false; |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 944 | |
| 945 | // Verify that loop exiting block has only two predecessor, where one predecessor |
| 946 | // is split condition block. The other predecessor will become exiting block's |
| 947 | // dominator after CFG is updated. TODO : Handle CFG's where exiting block has |
| 948 | // more then two predecessors. This requires extra work in updating dominator |
| 949 | // information. |
| 950 | BasicBlock *ExitingBBPred = NULL; |
| 951 | for (pred_iterator PI = pred_begin(ExitingBlock), PE = pred_end(ExitingBlock); |
| 952 | PI != PE; ++PI) { |
| 953 | BasicBlock *BB = *PI; |
| 954 | if (SplitCondBlock == BB) |
| 955 | continue; |
| 956 | if (ExitingBBPred) |
| 957 | return false; |
| 958 | else |
| 959 | ExitingBBPred = BB; |
| 960 | } |
| 961 | |
| 962 | // Update loop bounds to absorb Op0 check. |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 963 | updateLoopBounds(Op0); |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 964 | // Update loop bounds to absorb Op1 check. |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 965 | updateLoopBounds(Op1); |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 966 | |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 967 | // Update CFG |
Devang Patel | 453a844 | 2007-09-25 17:31:19 +0000 | [diff] [blame] | 968 | |
| 969 | // Unconditionally connect split block to its remaining successor. |
| 970 | BranchInst *SplitTerminator = |
| 971 | cast<BranchInst>(SplitCondBlock->getTerminator()); |
| 972 | BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| 973 | BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
| 974 | if (Succ0 == ExitCondition->getParent()) |
| 975 | SplitTerminator->setUnconditionalDest(Succ1); |
| 976 | else |
| 977 | SplitTerminator->setUnconditionalDest(Succ0); |
| 978 | |
| 979 | // Remove split condition. |
| 980 | SD.SplitCondition->eraseFromParent(); |
| 981 | if (Op0->use_begin() == Op0->use_end()) |
| 982 | Op0->eraseFromParent(); |
| 983 | if (Op1->use_begin() == Op1->use_end()) |
| 984 | Op1->eraseFromParent(); |
| 985 | |
| 986 | BranchInst *ExitInsn = |
| 987 | dyn_cast<BranchInst>(ExitingBlock->getTerminator()); |
| 988 | assert (ExitInsn && "Unable to find suitable loop exit branch"); |
| 989 | BasicBlock *ExitBlock = ExitInsn->getSuccessor(1); |
| 990 | if (L->contains(ExitBlock)) |
| 991 | ExitBlock = ExitInsn->getSuccessor(0); |
| 992 | |
| 993 | // Update domiantor info. Now, ExitingBlock has only one predecessor, |
| 994 | // ExitingBBPred, and it is ExitingBlock's immediate domiantor. |
| 995 | DT->changeImmediateDominator(ExitingBlock, ExitingBBPred); |
| 996 | |
| 997 | // If ExitingBlock is a member of loop BB's DF list then replace it with |
| 998 | // loop header and exit block. |
| 999 | for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); |
| 1000 | I != E; ++I) { |
| 1001 | BasicBlock *BB = *I; |
| 1002 | if (BB == Header || BB == ExitingBlock) |
| 1003 | continue; |
| 1004 | DominanceFrontier::iterator BBDF = DF->find(BB); |
| 1005 | DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin(); |
| 1006 | DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end(); |
| 1007 | while (DomSetI != DomSetE) { |
| 1008 | DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI; |
| 1009 | ++DomSetI; |
| 1010 | BasicBlock *DFBB = *CurrentItr; |
| 1011 | if (DFBB == ExitingBlock) { |
| 1012 | BBDF->second.erase(DFBB); |
| 1013 | BBDF->second.insert(Header); |
| 1014 | if (Header != ExitingBlock) |
| 1015 | BBDF->second.insert(ExitBlock); |
| 1016 | } |
| 1017 | } |
| 1018 | } |
| 1019 | |
Devang Patel | 1c01350 | 2007-09-25 17:43:08 +0000 | [diff] [blame] | 1020 | return true; |
Devang Patel | 5279d06 | 2007-09-17 20:39:48 +0000 | [diff] [blame] | 1021 | } |
| 1022 | |
| 1023 | |
Devang Patel | a6a8663 | 2007-08-14 18:35:57 +0000 | [diff] [blame] | 1024 | /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB. |
| 1025 | /// This routine is used to remove split condition's dead branch, dominated by |
| 1026 | /// DeadBB. LiveBB dominates split conidition's other branch. |
| 1027 | void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP, |
| 1028 | BasicBlock *LiveBB) { |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1029 | |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1030 | // First update DeadBB's dominance frontier. |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1031 | SmallVector<BasicBlock *, 8> FrontierBBs; |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1032 | DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB); |
| 1033 | if (DeadBBDF != DF->end()) { |
| 1034 | SmallVector<BasicBlock *, 8> PredBlocks; |
| 1035 | |
| 1036 | DominanceFrontier::DomSetType DeadBBSet = DeadBBDF->second; |
| 1037 | for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(), |
| 1038 | DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) { |
| 1039 | BasicBlock *FrontierBB = *DeadBBSetI; |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1040 | FrontierBBs.push_back(FrontierBB); |
| 1041 | |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1042 | // Rremove any PHI incoming edge from blocks dominated by DeadBB. |
| 1043 | PredBlocks.clear(); |
| 1044 | for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB); |
| 1045 | PI != PE; ++PI) { |
| 1046 | BasicBlock *P = *PI; |
| 1047 | if (P == DeadBB || DT->dominates(DeadBB, P)) |
| 1048 | PredBlocks.push_back(P); |
Devang Patel | fc4c5f8 | 2007-08-13 22:13:24 +0000 | [diff] [blame] | 1049 | } |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1050 | |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1051 | for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end(); |
| 1052 | FBI != FBE; ++FBI) { |
| 1053 | if (PHINode *PN = dyn_cast<PHINode>(FBI)) { |
| 1054 | for(SmallVector<BasicBlock *, 8>::iterator PI = PredBlocks.begin(), |
| 1055 | PE = PredBlocks.end(); PI != PE; ++PI) { |
| 1056 | BasicBlock *P = *PI; |
| 1057 | PN->removeIncomingValue(P); |
| 1058 | } |
| 1059 | } |
| 1060 | else |
| 1061 | break; |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1062 | } |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1063 | } |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1064 | } |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1065 | |
| 1066 | // Now remove DeadBB and all nodes dominated by DeadBB in df order. |
| 1067 | SmallVector<BasicBlock *, 32> WorkList; |
| 1068 | DomTreeNode *DN = DT->getNode(DeadBB); |
| 1069 | for (df_iterator<DomTreeNode*> DI = df_begin(DN), |
| 1070 | E = df_end(DN); DI != E; ++DI) { |
| 1071 | BasicBlock *BB = DI->getBlock(); |
| 1072 | WorkList.push_back(BB); |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1073 | BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy)); |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1074 | } |
| 1075 | |
| 1076 | while (!WorkList.empty()) { |
| 1077 | BasicBlock *BB = WorkList.back(); WorkList.pop_back(); |
| 1078 | for(BasicBlock::iterator BBI = BB->begin(), BBE = BB->end(); |
Devang Patel | d15dd8c | 2007-09-20 23:01:50 +0000 | [diff] [blame] | 1079 | BBI != BBE; ) { |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1080 | Instruction *I = BBI; |
Devang Patel | d15dd8c | 2007-09-20 23:01:50 +0000 | [diff] [blame] | 1081 | ++BBI; |
Devang Patel | 5b8ec61 | 2007-08-15 03:31:47 +0000 | [diff] [blame] | 1082 | I->replaceAllUsesWith(UndefValue::get(I->getType())); |
| 1083 | I->eraseFromParent(); |
| 1084 | } |
| 1085 | LPM->deleteSimpleAnalysisValue(BB, LP); |
| 1086 | DT->eraseNode(BB); |
| 1087 | DF->removeBlock(BB); |
| 1088 | LI->removeBlock(BB); |
| 1089 | BB->eraseFromParent(); |
| 1090 | } |
Devang Patel | 96bf524 | 2007-08-17 21:59:16 +0000 | [diff] [blame] | 1091 | |
| 1092 | // Update Frontier BBs' dominator info. |
| 1093 | while (!FrontierBBs.empty()) { |
| 1094 | BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back(); |
| 1095 | BasicBlock *NewDominator = FBB->getSinglePredecessor(); |
| 1096 | if (!NewDominator) { |
| 1097 | pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB); |
| 1098 | NewDominator = *PI; |
| 1099 | ++PI; |
| 1100 | if (NewDominator != LiveBB) { |
| 1101 | for(; PI != PE; ++PI) { |
| 1102 | BasicBlock *P = *PI; |
| 1103 | if (P == LiveBB) { |
| 1104 | NewDominator = LiveBB; |
| 1105 | break; |
| 1106 | } |
| 1107 | NewDominator = DT->findNearestCommonDominator(NewDominator, P); |
| 1108 | } |
| 1109 | } |
| 1110 | } |
| 1111 | assert (NewDominator && "Unable to fix dominator info."); |
| 1112 | DT->changeImmediateDominator(FBB, NewDominator); |
| 1113 | DF->changeImmediateDominator(FBB, NewDominator, DT); |
| 1114 | } |
| 1115 | |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1116 | } |
| 1117 | |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1118 | /// safeSplitCondition - Return true if it is possible to |
| 1119 | /// split loop using given split condition. |
| 1120 | bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) { |
Devang Patel | 23a19f8 | 2007-08-10 00:53:35 +0000 | [diff] [blame] | 1121 | |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1122 | BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
Devang Patel | 8893ca6 | 2007-09-17 21:01:05 +0000 | [diff] [blame] | 1123 | BasicBlock *Latch = L->getLoopLatch(); |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1124 | BranchInst *SplitTerminator = |
| 1125 | cast<BranchInst>(SplitCondBlock->getTerminator()); |
| 1126 | BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| 1127 | BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
Devang Patel | 20d260a | 2007-08-18 00:00:32 +0000 | [diff] [blame] | 1128 | |
Devang Patel | b88e420 | 2007-08-24 05:36:56 +0000 | [diff] [blame] | 1129 | // Finally this split condition is safe only if merge point for |
| 1130 | // split condition branch is loop latch. This check along with previous |
| 1131 | // check, to ensure that exit condition is in either loop latch or header, |
| 1132 | // filters all loops with non-empty loop body between merge point |
| 1133 | // and exit condition. |
| 1134 | DominanceFrontier::iterator Succ0DF = DF->find(Succ0); |
| 1135 | assert (Succ0DF != DF->end() && "Unable to find Succ0 dominance frontier"); |
| 1136 | if (Succ0DF->second.count(Latch)) |
| 1137 | return true; |
| 1138 | |
| 1139 | DominanceFrontier::iterator Succ1DF = DF->find(Succ1); |
| 1140 | assert (Succ1DF != DF->end() && "Unable to find Succ1 dominance frontier"); |
| 1141 | if (Succ1DF->second.count(Latch)) |
| 1142 | return true; |
| 1143 | |
| 1144 | return false; |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1145 | } |
| 1146 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1147 | /// calculateLoopBounds - ALoop exit value and BLoop start values are calculated |
| 1148 | /// based on split value. |
| 1149 | void LoopIndexSplit::calculateLoopBounds(SplitInfo &SD) { |
| 1150 | |
Devang Patel | 4f12c5f | 2007-09-11 00:12:56 +0000 | [diff] [blame] | 1151 | ICmpInst *SC = cast<ICmpInst>(SD.SplitCondition); |
| 1152 | ICmpInst::Predicate SP = SC->getPredicate(); |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1153 | const Type *Ty = SD.SplitValue->getType(); |
| 1154 | bool Sign = ExitCondition->isSignedPredicate(); |
| 1155 | BasicBlock *Preheader = L->getLoopPreheader(); |
| 1156 | Instruction *PHTerminator = Preheader->getTerminator(); |
| 1157 | |
| 1158 | // Initially use split value as upper loop bound for first loop and lower loop |
| 1159 | // bound for second loop. |
| 1160 | Value *AEV = SD.SplitValue; |
| 1161 | Value *BSV = SD.SplitValue; |
| 1162 | |
Devang Patel | babbe27 | 2007-09-19 00:28:47 +0000 | [diff] [blame] | 1163 | if (ExitCondition->getPredicate() == ICmpInst::ICMP_SGT |
| 1164 | || ExitCondition->getPredicate() == ICmpInst::ICMP_UGT |
| 1165 | || ExitCondition->getPredicate() == ICmpInst::ICMP_SGE |
| 1166 | || ExitCondition->getPredicate() == ICmpInst::ICMP_UGE) |
| 1167 | ExitCondition->swapOperands(); |
| 1168 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1169 | switch (ExitCondition->getPredicate()) { |
| 1170 | case ICmpInst::ICMP_SGT: |
| 1171 | case ICmpInst::ICMP_UGT: |
| 1172 | case ICmpInst::ICMP_SGE: |
| 1173 | case ICmpInst::ICMP_UGE: |
| 1174 | default: |
| 1175 | assert (0 && "Unexpected exit condition predicate"); |
| 1176 | |
| 1177 | case ICmpInst::ICMP_SLT: |
| 1178 | case ICmpInst::ICMP_ULT: |
| 1179 | { |
| 1180 | switch (SP) { |
| 1181 | case ICmpInst::ICMP_SLT: |
| 1182 | case ICmpInst::ICMP_ULT: |
| 1183 | // |
| 1184 | // for (i = LB; i < UB; ++i) { if (i < SV) A; else B; } |
| 1185 | // |
| 1186 | // is transformed into |
| 1187 | // AEV = BSV = SV |
| 1188 | // for (i = LB; i < min(UB, AEV); ++i) |
| 1189 | // A; |
| 1190 | // for (i = max(LB, BSV); i < UB; ++i); |
| 1191 | // B; |
| 1192 | break; |
| 1193 | case ICmpInst::ICMP_SLE: |
| 1194 | case ICmpInst::ICMP_ULE: |
| 1195 | { |
| 1196 | // |
| 1197 | // for (i = LB; i < UB; ++i) { if (i <= SV) A; else B; } |
| 1198 | // |
| 1199 | // is transformed into |
| 1200 | // |
| 1201 | // AEV = SV + 1 |
| 1202 | // BSV = SV + 1 |
| 1203 | // for (i = LB; i < min(UB, AEV); ++i) |
| 1204 | // A; |
| 1205 | // for (i = max(LB, BSV); i < UB; ++i) |
| 1206 | // B; |
| 1207 | BSV = BinaryOperator::createAdd(SD.SplitValue, |
| 1208 | ConstantInt::get(Ty, 1, Sign), |
| 1209 | "lsplit.add", PHTerminator); |
| 1210 | AEV = BSV; |
| 1211 | } |
| 1212 | break; |
| 1213 | case ICmpInst::ICMP_SGE: |
| 1214 | case ICmpInst::ICMP_UGE: |
| 1215 | // |
| 1216 | // for (i = LB; i < UB; ++i) { if (i >= SV) A; else B; } |
| 1217 | // |
| 1218 | // is transformed into |
| 1219 | // AEV = BSV = SV |
| 1220 | // for (i = LB; i < min(UB, AEV); ++i) |
| 1221 | // B; |
| 1222 | // for (i = max(BSV, LB); i < UB; ++i) |
| 1223 | // A; |
| 1224 | break; |
| 1225 | case ICmpInst::ICMP_SGT: |
| 1226 | case ICmpInst::ICMP_UGT: |
| 1227 | { |
| 1228 | // |
| 1229 | // for (i = LB; i < UB; ++i) { if (i > SV) A; else B; } |
| 1230 | // |
| 1231 | // is transformed into |
| 1232 | // |
| 1233 | // BSV = AEV = SV + 1 |
| 1234 | // for (i = LB; i < min(UB, AEV); ++i) |
| 1235 | // B; |
| 1236 | // for (i = max(LB, BSV); i < UB; ++i) |
| 1237 | // A; |
| 1238 | BSV = BinaryOperator::createAdd(SD.SplitValue, |
| 1239 | ConstantInt::get(Ty, 1, Sign), |
| 1240 | "lsplit.add", PHTerminator); |
| 1241 | AEV = BSV; |
| 1242 | } |
| 1243 | break; |
| 1244 | default: |
| 1245 | assert (0 && "Unexpected split condition predicate"); |
| 1246 | break; |
| 1247 | } // end switch (SP) |
| 1248 | } |
| 1249 | break; |
| 1250 | case ICmpInst::ICMP_SLE: |
| 1251 | case ICmpInst::ICMP_ULE: |
| 1252 | { |
| 1253 | switch (SP) { |
| 1254 | case ICmpInst::ICMP_SLT: |
| 1255 | case ICmpInst::ICMP_ULT: |
| 1256 | // |
| 1257 | // for (i = LB; i <= UB; ++i) { if (i < SV) A; else B; } |
| 1258 | // |
| 1259 | // is transformed into |
| 1260 | // AEV = SV - 1; |
| 1261 | // BSV = SV; |
| 1262 | // for (i = LB; i <= min(UB, AEV); ++i) |
| 1263 | // A; |
| 1264 | // for (i = max(LB, BSV); i <= UB; ++i) |
| 1265 | // B; |
| 1266 | AEV = BinaryOperator::createSub(SD.SplitValue, |
| 1267 | ConstantInt::get(Ty, 1, Sign), |
| 1268 | "lsplit.sub", PHTerminator); |
| 1269 | break; |
| 1270 | case ICmpInst::ICMP_SLE: |
| 1271 | case ICmpInst::ICMP_ULE: |
| 1272 | // |
| 1273 | // for (i = LB; i <= UB; ++i) { if (i <= SV) A; else B; } |
| 1274 | // |
| 1275 | // is transformed into |
| 1276 | // AEV = SV; |
| 1277 | // BSV = SV + 1; |
| 1278 | // for (i = LB; i <= min(UB, AEV); ++i) |
| 1279 | // A; |
| 1280 | // for (i = max(LB, BSV); i <= UB; ++i) |
| 1281 | // B; |
| 1282 | BSV = BinaryOperator::createAdd(SD.SplitValue, |
| 1283 | ConstantInt::get(Ty, 1, Sign), |
| 1284 | "lsplit.add", PHTerminator); |
| 1285 | break; |
| 1286 | case ICmpInst::ICMP_SGT: |
| 1287 | case ICmpInst::ICMP_UGT: |
| 1288 | // |
| 1289 | // for (i = LB; i <= UB; ++i) { if (i > SV) A; else B; } |
| 1290 | // |
| 1291 | // is transformed into |
| 1292 | // AEV = SV; |
| 1293 | // BSV = SV + 1; |
| 1294 | // for (i = LB; i <= min(AEV, UB); ++i) |
| 1295 | // B; |
| 1296 | // for (i = max(LB, BSV); i <= UB; ++i) |
| 1297 | // A; |
| 1298 | BSV = BinaryOperator::createAdd(SD.SplitValue, |
| 1299 | ConstantInt::get(Ty, 1, Sign), |
| 1300 | "lsplit.add", PHTerminator); |
| 1301 | break; |
| 1302 | case ICmpInst::ICMP_SGE: |
| 1303 | case ICmpInst::ICMP_UGE: |
| 1304 | // ** TODO ** |
| 1305 | // |
| 1306 | // for (i = LB; i <= UB; ++i) { if (i >= SV) A; else B; } |
| 1307 | // |
| 1308 | // is transformed into |
| 1309 | // AEV = SV - 1; |
| 1310 | // BSV = SV; |
| 1311 | // for (i = LB; i <= min(AEV, UB); ++i) |
| 1312 | // B; |
| 1313 | // for (i = max(LB, BSV); i <= UB; ++i) |
| 1314 | // A; |
| 1315 | AEV = BinaryOperator::createSub(SD.SplitValue, |
| 1316 | ConstantInt::get(Ty, 1, Sign), |
| 1317 | "lsplit.sub", PHTerminator); |
| 1318 | break; |
| 1319 | default: |
| 1320 | assert (0 && "Unexpected split condition predicate"); |
| 1321 | break; |
| 1322 | } // end switch (SP) |
| 1323 | } |
| 1324 | break; |
| 1325 | } |
| 1326 | |
| 1327 | // Calculate ALoop induction variable's new exiting value and |
| 1328 | // BLoop induction variable's new starting value. Calculuate these |
| 1329 | // values in original loop's preheader. |
| 1330 | // A_ExitValue = min(SplitValue, OrignalLoopExitValue) |
| 1331 | // B_StartValue = max(SplitValue, OriginalLoopStartValue) |
Devang Patel | 3f65f02 | 2007-09-21 21:18:19 +0000 | [diff] [blame] | 1332 | Instruction *InsertPt = L->getHeader()->getFirstNonPHI(); |
Devang Patel | 5ffdc56 | 2007-12-03 19:17:21 +0000 | [diff] [blame] | 1333 | |
| 1334 | // If ExitValue operand is also defined in Loop header then |
| 1335 | // insert new ExitValue after this operand definition. |
| 1336 | if (Instruction *EVN = |
| 1337 | dyn_cast<Instruction>(ExitCondition->getOperand(ExitValueNum))) { |
| 1338 | if (!isa<PHINode>(EVN)) |
| 1339 | if (InsertPt->getParent() == EVN->getParent()) { |
| 1340 | BasicBlock::iterator LHBI = L->getHeader()->begin(); |
| 1341 | BasicBlock::iterator LHBE = L->getHeader()->end(); |
| 1342 | for(;LHBI != LHBE; ++LHBI) { |
| 1343 | Instruction *I = LHBI; |
| 1344 | if (I == EVN) |
| 1345 | break; |
| 1346 | } |
| 1347 | InsertPt = ++LHBI; |
| 1348 | } |
| 1349 | } |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1350 | Value *C1 = new ICmpInst(Sign ? |
| 1351 | ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 1352 | AEV, |
| 1353 | ExitCondition->getOperand(ExitValueNum), |
Devang Patel | 3f65f02 | 2007-09-21 21:18:19 +0000 | [diff] [blame] | 1354 | "lsplit.ev", InsertPt); |
| 1355 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1356 | SD.A_ExitValue = new SelectInst(C1, AEV, |
| 1357 | ExitCondition->getOperand(ExitValueNum), |
Devang Patel | 3f65f02 | 2007-09-21 21:18:19 +0000 | [diff] [blame] | 1358 | "lsplit.ev", InsertPt); |
| 1359 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1360 | Value *C2 = new ICmpInst(Sign ? |
| 1361 | ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, |
| 1362 | BSV, StartValue, "lsplit.sv", |
| 1363 | PHTerminator); |
| 1364 | SD.B_StartValue = new SelectInst(C2, StartValue, BSV, |
| 1365 | "lsplit.sv", PHTerminator); |
| 1366 | } |
| 1367 | |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1368 | /// splitLoop - Split current loop L in two loops using split information |
| 1369 | /// SD. Update dominator information. Maintain LCSSA form. |
| 1370 | bool LoopIndexSplit::splitLoop(SplitInfo &SD) { |
| 1371 | |
| 1372 | if (!safeSplitCondition(SD)) |
| 1373 | return false; |
| 1374 | |
Devang Patel | 8893ca6 | 2007-09-17 21:01:05 +0000 | [diff] [blame] | 1375 | BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); |
| 1376 | |
| 1377 | // Unable to handle triange loops at the moment. |
| 1378 | // In triangle loop, split condition is in header and one of the |
| 1379 | // the split destination is loop latch. If split condition is EQ |
| 1380 | // then such loops are already handle in processOneIterationLoop(). |
| 1381 | BasicBlock *Latch = L->getLoopLatch(); |
| 1382 | BranchInst *SplitTerminator = |
| 1383 | cast<BranchInst>(SplitCondBlock->getTerminator()); |
| 1384 | BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); |
| 1385 | BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); |
| 1386 | if (L->getHeader() == SplitCondBlock |
| 1387 | && (Latch == Succ0 || Latch == Succ1)) |
| 1388 | return false; |
| 1389 | |
| 1390 | // If split condition branches heads do not have single predecessor, |
| 1391 | // SplitCondBlock, then is not possible to remove inactive branch. |
| 1392 | if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor()) |
| 1393 | return false; |
| 1394 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1395 | // After loop is cloned there are two loops. |
| 1396 | // |
| 1397 | // First loop, referred as ALoop, executes first part of loop's iteration |
| 1398 | // space split. Second loop, referred as BLoop, executes remaining |
| 1399 | // part of loop's iteration space. |
| 1400 | // |
| 1401 | // ALoop's exit edge enters BLoop's header through a forwarding block which |
| 1402 | // acts as a BLoop's preheader. |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1403 | BasicBlock *Preheader = L->getLoopPreheader(); |
Devang Patel | dc52395 | 2007-08-22 18:27:01 +0000 | [diff] [blame] | 1404 | |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1405 | // Calculate ALoop induction variable's new exiting value and |
| 1406 | // BLoop induction variable's new starting value. |
| 1407 | calculateLoopBounds(SD); |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 1408 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1409 | //[*] Clone loop. |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1410 | DenseMap<const Value *, Value *> ValueMap; |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1411 | Loop *BLoop = CloneLoop(L, LPM, LI, ValueMap, this); |
Devang Patel | d79faee | 2007-08-25 02:39:24 +0000 | [diff] [blame] | 1412 | Loop *ALoop = L; |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1413 | BasicBlock *B_Header = BLoop->getHeader(); |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1414 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1415 | //[*] ALoop's exiting edge BLoop's header. |
| 1416 | // ALoop's original exit block becomes BLoop's exit block. |
| 1417 | PHINode *B_IndVar = cast<PHINode>(ValueMap[IndVar]); |
| 1418 | BasicBlock *A_ExitingBlock = ExitCondition->getParent(); |
| 1419 | BranchInst *A_ExitInsn = |
| 1420 | dyn_cast<BranchInst>(A_ExitingBlock->getTerminator()); |
| 1421 | assert (A_ExitInsn && "Unable to find suitable loop exit branch"); |
| 1422 | BasicBlock *B_ExitBlock = A_ExitInsn->getSuccessor(1); |
| 1423 | if (L->contains(B_ExitBlock)) { |
| 1424 | B_ExitBlock = A_ExitInsn->getSuccessor(0); |
| 1425 | A_ExitInsn->setSuccessor(0, B_Header); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1426 | } else |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1427 | A_ExitInsn->setSuccessor(1, B_Header); |
| 1428 | |
| 1429 | //[*] Update ALoop's exit value using new exit value. |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1430 | ExitCondition->setOperand(ExitValueNum, SD.A_ExitValue); |
Devang Patel | 0b8e02b | 2007-08-21 21:12:02 +0000 | [diff] [blame] | 1431 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1432 | // [*] Update BLoop's header phi nodes. Remove incoming PHINode's from |
| 1433 | // original loop's preheader. Add incoming PHINode values from |
| 1434 | // ALoop's exiting block. Update BLoop header's domiantor info. |
| 1435 | |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1436 | // Collect inverse map of Header PHINodes. |
| 1437 | DenseMap<Value *, Value *> InverseMap; |
| 1438 | for (BasicBlock::iterator BI = L->getHeader()->begin(), |
| 1439 | BE = L->getHeader()->end(); BI != BE; ++BI) { |
| 1440 | if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
| 1441 | PHINode *PNClone = cast<PHINode>(ValueMap[PN]); |
| 1442 | InverseMap[PNClone] = PN; |
| 1443 | } else |
| 1444 | break; |
| 1445 | } |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1446 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1447 | for (BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end(); |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1448 | BI != BE; ++BI) { |
| 1449 | if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1450 | // Remove incoming value from original preheader. |
| 1451 | PN->removeIncomingValue(Preheader); |
| 1452 | |
| 1453 | // Add incoming value from A_ExitingBlock. |
| 1454 | if (PN == B_IndVar) |
Devang Patel | 4a69da9 | 2007-08-25 00:56:38 +0000 | [diff] [blame] | 1455 | PN->addIncoming(SD.B_StartValue, A_ExitingBlock); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1456 | else { |
| 1457 | PHINode *OrigPN = cast<PHINode>(InverseMap[PN]); |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1458 | Value *V2 = OrigPN->getIncomingValueForBlock(A_ExitingBlock); |
| 1459 | PN->addIncoming(V2, A_ExitingBlock); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1460 | } |
| 1461 | } else |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1462 | break; |
| 1463 | } |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1464 | DT->changeImmediateDominator(B_Header, A_ExitingBlock); |
| 1465 | DF->changeImmediateDominator(B_Header, A_ExitingBlock, DT); |
Devang Patel | 0b8e02b | 2007-08-21 21:12:02 +0000 | [diff] [blame] | 1466 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1467 | // [*] Update BLoop's exit block. Its new predecessor is BLoop's exit |
| 1468 | // block. Remove incoming PHINode values from ALoop's exiting block. |
| 1469 | // Add new incoming values from BLoop's incoming exiting value. |
| 1470 | // Update BLoop exit block's dominator info.. |
| 1471 | BasicBlock *B_ExitingBlock = cast<BasicBlock>(ValueMap[A_ExitingBlock]); |
| 1472 | for (BasicBlock::iterator BI = B_ExitBlock->begin(), BE = B_ExitBlock->end(); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1473 | BI != BE; ++BI) { |
| 1474 | if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1475 | PN->addIncoming(ValueMap[PN->getIncomingValueForBlock(A_ExitingBlock)], |
| 1476 | B_ExitingBlock); |
| 1477 | PN->removeIncomingValue(A_ExitingBlock); |
Devang Patel | ada054a | 2007-08-14 01:30:57 +0000 | [diff] [blame] | 1478 | } else |
| 1479 | break; |
| 1480 | } |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1481 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1482 | DT->changeImmediateDominator(B_ExitBlock, B_ExitingBlock); |
| 1483 | DF->changeImmediateDominator(B_ExitBlock, B_ExitingBlock, DT); |
Devang Patel | fc4c5f8 | 2007-08-13 22:13:24 +0000 | [diff] [blame] | 1484 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1485 | //[*] Split ALoop's exit edge. This creates a new block which |
| 1486 | // serves two purposes. First one is to hold PHINode defnitions |
| 1487 | // to ensure that ALoop's LCSSA form. Second use it to act |
| 1488 | // as a preheader for BLoop. |
| 1489 | BasicBlock *A_ExitBlock = SplitEdge(A_ExitingBlock, B_Header, this); |
Devang Patel | 423c8b2 | 2007-08-10 18:07:13 +0000 | [diff] [blame] | 1490 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1491 | //[*] Preserve ALoop's LCSSA form. Create new forwarding PHINodes |
| 1492 | // in A_ExitBlock to redefine outgoing PHI definitions from ALoop. |
| 1493 | for(BasicBlock::iterator BI = B_Header->begin(), BE = B_Header->end(); |
Devang Patel | 60cbab4 | 2007-08-21 19:47:46 +0000 | [diff] [blame] | 1494 | BI != BE; ++BI) { |
| 1495 | if (PHINode *PN = dyn_cast<PHINode>(BI)) { |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1496 | Value *V1 = PN->getIncomingValueForBlock(A_ExitBlock); |
Devang Patel | 60cbab4 | 2007-08-21 19:47:46 +0000 | [diff] [blame] | 1497 | PHINode *newPHI = new PHINode(PN->getType(), PN->getName()); |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1498 | newPHI->addIncoming(V1, A_ExitingBlock); |
| 1499 | A_ExitBlock->getInstList().push_front(newPHI); |
| 1500 | PN->removeIncomingValue(A_ExitBlock); |
| 1501 | PN->addIncoming(newPHI, A_ExitBlock); |
Devang Patel | 60cbab4 | 2007-08-21 19:47:46 +0000 | [diff] [blame] | 1502 | } else |
| 1503 | break; |
| 1504 | } |
| 1505 | |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1506 | //[*] Eliminate split condition's inactive branch from ALoop. |
| 1507 | BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent(); |
| 1508 | BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator()); |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 1509 | BasicBlock *A_InactiveBranch = NULL; |
| 1510 | BasicBlock *A_ActiveBranch = NULL; |
| 1511 | if (SD.UseTrueBranchFirst) { |
| 1512 | A_ActiveBranch = A_BR->getSuccessor(0); |
| 1513 | A_InactiveBranch = A_BR->getSuccessor(1); |
| 1514 | } else { |
| 1515 | A_ActiveBranch = A_BR->getSuccessor(1); |
| 1516 | A_InactiveBranch = A_BR->getSuccessor(0); |
| 1517 | } |
Devang Patel | 7097e9a | 2007-08-24 19:32:26 +0000 | [diff] [blame] | 1518 | A_BR->setUnconditionalDest(A_ActiveBranch); |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1519 | removeBlocks(A_InactiveBranch, L, A_ActiveBranch); |
| 1520 | |
| 1521 | //[*] Eliminate split condition's inactive branch in from BLoop. |
| 1522 | BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]); |
| 1523 | BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator()); |
Devang Patel | 4259fe3 | 2007-08-24 06:17:19 +0000 | [diff] [blame] | 1524 | BasicBlock *B_InactiveBranch = NULL; |
| 1525 | BasicBlock *B_ActiveBranch = NULL; |
| 1526 | if (SD.UseTrueBranchFirst) { |
| 1527 | B_ActiveBranch = B_BR->getSuccessor(1); |
| 1528 | B_InactiveBranch = B_BR->getSuccessor(0); |
| 1529 | } else { |
| 1530 | B_ActiveBranch = B_BR->getSuccessor(0); |
| 1531 | B_InactiveBranch = B_BR->getSuccessor(1); |
| 1532 | } |
Devang Patel | 7097e9a | 2007-08-24 19:32:26 +0000 | [diff] [blame] | 1533 | B_BR->setUnconditionalDest(B_ActiveBranch); |
Devang Patel | a8644e3 | 2007-08-22 19:33:29 +0000 | [diff] [blame] | 1534 | removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch); |
| 1535 | |
Devang Patel | d79faee | 2007-08-25 02:39:24 +0000 | [diff] [blame] | 1536 | BasicBlock *A_Header = L->getHeader(); |
| 1537 | if (A_ExitingBlock == A_Header) |
| 1538 | return true; |
| 1539 | |
| 1540 | //[*] Move exit condition into split condition block to avoid |
| 1541 | // executing dead loop iteration. |
| 1542 | ICmpInst *B_ExitCondition = cast<ICmpInst>(ValueMap[ExitCondition]); |
| 1543 | Instruction *B_IndVarIncrement = cast<Instruction>(ValueMap[IndVarIncrement]); |
| 1544 | ICmpInst *B_SplitCondition = cast<ICmpInst>(ValueMap[SD.SplitCondition]); |
| 1545 | |
| 1546 | moveExitCondition(A_SplitCondBlock, A_ActiveBranch, A_ExitBlock, ExitCondition, |
Devang Patel | 4f12c5f | 2007-09-11 00:12:56 +0000 | [diff] [blame] | 1547 | cast<ICmpInst>(SD.SplitCondition), IndVar, IndVarIncrement, |
| 1548 | ALoop); |
Devang Patel | d79faee | 2007-08-25 02:39:24 +0000 | [diff] [blame] | 1549 | |
| 1550 | moveExitCondition(B_SplitCondBlock, B_ActiveBranch, B_ExitBlock, B_ExitCondition, |
| 1551 | B_SplitCondition, B_IndVar, B_IndVarIncrement, BLoop); |
| 1552 | |
Devang Patel | 98147a3 | 2007-08-12 07:02:51 +0000 | [diff] [blame] | 1553 | return true; |
Devang Patel | fee76bd | 2007-08-07 00:25:56 +0000 | [diff] [blame] | 1554 | } |
Devang Patel | d79faee | 2007-08-25 02:39:24 +0000 | [diff] [blame] | 1555 | |
| 1556 | // moveExitCondition - Move exit condition EC into split condition block CondBB. |
| 1557 | void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB, |
| 1558 | BasicBlock *ExitBB, ICmpInst *EC, ICmpInst *SC, |
| 1559 | PHINode *IV, Instruction *IVAdd, Loop *LP) { |
| 1560 | |
| 1561 | BasicBlock *ExitingBB = EC->getParent(); |
| 1562 | Instruction *CurrentBR = CondBB->getTerminator(); |
| 1563 | |
| 1564 | // Move exit condition into split condition block. |
| 1565 | EC->moveBefore(CurrentBR); |
| 1566 | EC->setOperand(ExitValueNum == 0 ? 1 : 0, IV); |
| 1567 | |
| 1568 | // Move exiting block's branch into split condition block. Update its branch |
| 1569 | // destination. |
| 1570 | BranchInst *ExitingBR = cast<BranchInst>(ExitingBB->getTerminator()); |
| 1571 | ExitingBR->moveBefore(CurrentBR); |
| 1572 | if (ExitingBR->getSuccessor(0) == ExitBB) |
| 1573 | ExitingBR->setSuccessor(1, ActiveBB); |
| 1574 | else |
| 1575 | ExitingBR->setSuccessor(0, ActiveBB); |
| 1576 | |
| 1577 | // Remove split condition and current split condition branch. |
| 1578 | SC->eraseFromParent(); |
| 1579 | CurrentBR->eraseFromParent(); |
| 1580 | |
| 1581 | // Connect exiting block to split condition block. |
| 1582 | new BranchInst(CondBB, ExitingBB); |
| 1583 | |
| 1584 | // Update PHINodes |
| 1585 | updatePHINodes(ExitBB, ExitingBB, CondBB, IV, IVAdd); |
| 1586 | |
| 1587 | // Fix dominator info. |
| 1588 | // ExitBB is now dominated by CondBB |
| 1589 | DT->changeImmediateDominator(ExitBB, CondBB); |
| 1590 | DF->changeImmediateDominator(ExitBB, CondBB, DT); |
| 1591 | |
| 1592 | // Basicblocks dominated by ActiveBB may have ExitingBB or |
| 1593 | // a basic block outside the loop in their DF list. If so, |
| 1594 | // replace it with CondBB. |
| 1595 | DomTreeNode *Node = DT->getNode(ActiveBB); |
| 1596 | for (df_iterator<DomTreeNode *> DI = df_begin(Node), DE = df_end(Node); |
| 1597 | DI != DE; ++DI) { |
| 1598 | BasicBlock *BB = DI->getBlock(); |
| 1599 | DominanceFrontier::iterator BBDF = DF->find(BB); |
| 1600 | DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin(); |
| 1601 | DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end(); |
| 1602 | while (DomSetI != DomSetE) { |
| 1603 | DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI; |
| 1604 | ++DomSetI; |
| 1605 | BasicBlock *DFBB = *CurrentItr; |
| 1606 | if (DFBB == ExitingBB || !L->contains(DFBB)) { |
| 1607 | BBDF->second.erase(DFBB); |
| 1608 | BBDF->second.insert(CondBB); |
| 1609 | } |
| 1610 | } |
| 1611 | } |
| 1612 | } |
| 1613 | |
| 1614 | /// updatePHINodes - CFG has been changed. |
| 1615 | /// Before |
| 1616 | /// - ExitBB's single predecessor was Latch |
| 1617 | /// - Latch's second successor was Header |
| 1618 | /// Now |
| 1619 | /// - ExitBB's single predecessor was Header |
| 1620 | /// - Latch's one and only successor was Header |
| 1621 | /// |
| 1622 | /// Update ExitBB PHINodes' to reflect this change. |
| 1623 | void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, |
| 1624 | BasicBlock *Header, |
| 1625 | PHINode *IV, Instruction *IVIncrement) { |
| 1626 | |
| 1627 | for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end(); |
| 1628 | BI != BE; ++BI) { |
| 1629 | PHINode *PN = dyn_cast<PHINode>(BI); |
| 1630 | if (!PN) |
| 1631 | break; |
| 1632 | |
| 1633 | Value *V = PN->getIncomingValueForBlock(Latch); |
| 1634 | if (PHINode *PHV = dyn_cast<PHINode>(V)) { |
| 1635 | // PHV is in Latch. PHV has two uses, one use is in ExitBB PHINode |
| 1636 | // (i.e. PN :)). |
| 1637 | // The second use is in Header and it is new incoming value for PN. |
| 1638 | PHINode *U1 = NULL; |
| 1639 | PHINode *U2 = NULL; |
| 1640 | Value *NewV = NULL; |
| 1641 | for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end(); |
| 1642 | UI != E; ++UI) { |
| 1643 | if (!U1) |
| 1644 | U1 = cast<PHINode>(*UI); |
| 1645 | else if (!U2) |
| 1646 | U2 = cast<PHINode>(*UI); |
| 1647 | else |
| 1648 | assert ( 0 && "Unexpected third use of this PHINode"); |
| 1649 | } |
| 1650 | assert (U1 && U2 && "Unable to find two uses"); |
| 1651 | |
| 1652 | if (U1->getParent() == Header) |
| 1653 | NewV = U1; |
| 1654 | else |
| 1655 | NewV = U2; |
| 1656 | PN->addIncoming(NewV, Header); |
| 1657 | |
| 1658 | } else if (Instruction *PHI = dyn_cast<Instruction>(V)) { |
| 1659 | // If this instruction is IVIncrement then IV is new incoming value |
| 1660 | // from header otherwise this instruction must be incoming value from |
| 1661 | // header because loop is in LCSSA form. |
| 1662 | if (PHI == IVIncrement) |
| 1663 | PN->addIncoming(IV, Header); |
| 1664 | else |
| 1665 | PN->addIncoming(V, Header); |
| 1666 | } else |
| 1667 | // Otherwise this is an incoming value from header because loop is in |
| 1668 | // LCSSA form. |
| 1669 | PN->addIncoming(V, Header); |
| 1670 | |
| 1671 | // Remove incoming value from Latch. |
| 1672 | PN->removeIncomingValue(Latch); |
| 1673 | } |
| 1674 | } |