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Chris Lattner8383a7b2008-04-20 20:35:01 +00001//===- JumpThreading.cpp - Thread control through conditional blocks ------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
Chris Lattner177480b2008-04-20 21:13:06 +000010// This file implements the Jump Threading pass.
Chris Lattner8383a7b2008-04-20 20:35:01 +000011//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "jump-threading"
15#include "llvm/Transforms/Scalar.h"
Chris Lattner177480b2008-04-20 21:13:06 +000016#include "llvm/IntrinsicInst.h"
Owen Anderson1ff50b32009-07-03 00:54:20 +000017#include "llvm/LLVMContext.h"
Chris Lattner8383a7b2008-04-20 20:35:01 +000018#include "llvm/Pass.h"
Chris Lattner9819ef72009-11-09 23:00:14 +000019#include "llvm/Analysis/InstructionSimplify.h"
Chris Lattnercc4d3b22009-11-11 02:08:33 +000020#include "llvm/Analysis/LazyValueInfo.h"
Dan Gohmandd9344f2010-05-28 16:19:17 +000021#include "llvm/Analysis/Loads.h"
Chris Lattner2cc67512008-04-21 02:57:57 +000022#include "llvm/Transforms/Utils/BasicBlockUtils.h"
Chris Lattnerbd3401f2008-04-20 22:39:42 +000023#include "llvm/Transforms/Utils/Local.h"
Chris Lattner433a0db2009-10-10 09:05:58 +000024#include "llvm/Transforms/Utils/SSAUpdater.h"
Chris Lattneref0c6742008-12-01 04:48:07 +000025#include "llvm/Target/TargetData.h"
Mike Stumpfe095f32009-05-04 18:40:41 +000026#include "llvm/ADT/DenseMap.h"
Owen Andersoncb211902010-08-31 07:36:34 +000027#include "llvm/ADT/DenseSet.h"
Mike Stumpfe095f32009-05-04 18:40:41 +000028#include "llvm/ADT/Statistic.h"
29#include "llvm/ADT/STLExtras.h"
30#include "llvm/ADT/SmallPtrSet.h"
31#include "llvm/ADT/SmallSet.h"
Chris Lattner8383a7b2008-04-20 20:35:01 +000032#include "llvm/Support/CommandLine.h"
Chris Lattner177480b2008-04-20 21:13:06 +000033#include "llvm/Support/Debug.h"
Chris Lattner56608462009-12-28 08:20:46 +000034#include "llvm/Support/ValueHandle.h"
Daniel Dunbar93b67e42009-07-26 07:49:05 +000035#include "llvm/Support/raw_ostream.h"
Chris Lattner8383a7b2008-04-20 20:35:01 +000036using namespace llvm;
37
Chris Lattnerbd3401f2008-04-20 22:39:42 +000038STATISTIC(NumThreads, "Number of jumps threaded");
39STATISTIC(NumFolds, "Number of terminators folded");
Chris Lattner78c552e2009-10-11 07:24:57 +000040STATISTIC(NumDupes, "Number of branch blocks duplicated to eliminate phi");
Chris Lattner8383a7b2008-04-20 20:35:01 +000041
Chris Lattner177480b2008-04-20 21:13:06 +000042static cl::opt<unsigned>
Frits van Bommel6f9a8302010-12-05 19:02:47 +000043Threshold("jump-threading-threshold",
Chris Lattner177480b2008-04-20 21:13:06 +000044 cl::desc("Max block size to duplicate for jump threading"),
45 cl::init(6), cl::Hidden);
46
Chris Lattner8383a7b2008-04-20 20:35:01 +000047namespace {
Frits van Bommelea388f22010-12-05 19:06:41 +000048 // These are at global scope so static functions can use them too.
49 typedef SmallVectorImpl<std::pair<Constant*, BasicBlock*> > PredValueInfo;
50 typedef SmallVector<std::pair<Constant*, BasicBlock*>, 8> PredValueInfoTy;
51
Frits van Bommel6033b342010-12-06 23:36:56 +000052 // This is used to keep track of what kind of constant we're currently hoping
53 // to find.
54 enum ConstantPreference {
55 WantInteger,
56 WantBlockAddress
57 };
58
Chris Lattner94019f82008-05-09 04:43:13 +000059 /// This pass performs 'jump threading', which looks at blocks that have
60 /// multiple predecessors and multiple successors. If one or more of the
61 /// predecessors of the block can be proven to always jump to one of the
62 /// successors, we forward the edge from the predecessor to the successor by
63 /// duplicating the contents of this block.
64 ///
65 /// An example of when this can occur is code like this:
66 ///
67 /// if () { ...
68 /// X = 4;
69 /// }
70 /// if (X < 3) {
71 ///
72 /// In this case, the unconditional branch at the end of the first if can be
73 /// revectored to the false side of the second if.
74 ///
Chris Lattner3e8b6632009-09-02 06:11:42 +000075 class JumpThreading : public FunctionPass {
Chris Lattneref0c6742008-12-01 04:48:07 +000076 TargetData *TD;
Chris Lattnercc4d3b22009-11-11 02:08:33 +000077 LazyValueInfo *LVI;
Mike Stumpfe095f32009-05-04 18:40:41 +000078#ifdef NDEBUG
79 SmallPtrSet<BasicBlock*, 16> LoopHeaders;
80#else
81 SmallSet<AssertingVH<BasicBlock>, 16> LoopHeaders;
82#endif
Owen Andersoncb211902010-08-31 07:36:34 +000083 DenseSet<std::pair<Value*, BasicBlock*> > RecursionSet;
Frits van Bommel6f9a8302010-12-05 19:02:47 +000084
Owen Anderson9ba35362010-08-31 19:24:27 +000085 // RAII helper for updating the recursion stack.
86 struct RecursionSetRemover {
87 DenseSet<std::pair<Value*, BasicBlock*> > &TheSet;
88 std::pair<Value*, BasicBlock*> ThePair;
Frits van Bommel6f9a8302010-12-05 19:02:47 +000089
Owen Anderson9ba35362010-08-31 19:24:27 +000090 RecursionSetRemover(DenseSet<std::pair<Value*, BasicBlock*> > &S,
91 std::pair<Value*, BasicBlock*> P)
92 : TheSet(S), ThePair(P) { }
Frits van Bommel6f9a8302010-12-05 19:02:47 +000093
Owen Anderson9ba35362010-08-31 19:24:27 +000094 ~RecursionSetRemover() {
95 TheSet.erase(ThePair);
96 }
97 };
Chris Lattner8383a7b2008-04-20 20:35:01 +000098 public:
99 static char ID; // Pass identification
Owen Anderson081c34b2010-10-19 17:21:58 +0000100 JumpThreading() : FunctionPass(ID) {
101 initializeJumpThreadingPass(*PassRegistry::getPassRegistry());
102 }
Chris Lattner8383a7b2008-04-20 20:35:01 +0000103
104 bool runOnFunction(Function &F);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000105
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000106 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
Owen Andersonc809d902010-09-14 20:57:41 +0000107 AU.addRequired<LazyValueInfo>();
108 AU.addPreserved<LazyValueInfo>();
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000109 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000110
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000111 void FindLoopHeaders(Function &F);
Chris Lattnerc7bcbf62008-11-27 07:20:04 +0000112 bool ProcessBlock(BasicBlock *BB);
Chris Lattner5729d382009-11-07 08:05:03 +0000113 bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock*> &PredBBs,
114 BasicBlock *SuccBB);
Chris Lattner78c552e2009-10-11 07:24:57 +0000115 bool DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
Chris Lattner2249a0b2010-01-12 02:07:17 +0000116 const SmallVectorImpl<BasicBlock *> &PredBBs);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000117
Chris Lattner5729d382009-11-07 08:05:03 +0000118 bool ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
Frits van Bommel6033b342010-12-06 23:36:56 +0000119 PredValueInfo &Result,
120 ConstantPreference Preference);
121 bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
122 ConstantPreference Preference);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000123
124
Chris Lattner421fa9e2008-12-03 07:48:08 +0000125 bool ProcessBranchOnDuplicateCond(BasicBlock *PredBB, BasicBlock *DestBB);
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000126 bool ProcessSwitchOnDuplicateCond(BasicBlock *PredBB, BasicBlock *DestBB);
Chris Lattner6bf77502008-04-22 07:05:46 +0000127
Chris Lattner77beb472010-01-11 23:41:09 +0000128 bool ProcessBranchOnPHI(PHINode *PN);
Chris Lattner2249a0b2010-01-12 02:07:17 +0000129 bool ProcessBranchOnXOR(BinaryOperator *BO);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000130
Chris Lattner69e067f2008-11-27 05:07:53 +0000131 bool SimplifyPartiallyRedundantLoad(LoadInst *LI);
Chris Lattner8383a7b2008-04-20 20:35:01 +0000132 };
Chris Lattner8383a7b2008-04-20 20:35:01 +0000133}
134
Dan Gohman844731a2008-05-13 00:00:25 +0000135char JumpThreading::ID = 0;
Owen Anderson2ab36d32010-10-12 19:48:12 +0000136INITIALIZE_PASS_BEGIN(JumpThreading, "jump-threading",
137 "Jump Threading", false, false)
138INITIALIZE_PASS_DEPENDENCY(LazyValueInfo)
139INITIALIZE_PASS_END(JumpThreading, "jump-threading",
Owen Andersonce665bd2010-10-07 22:25:06 +0000140 "Jump Threading", false, false)
Dan Gohman844731a2008-05-13 00:00:25 +0000141
Chris Lattner8383a7b2008-04-20 20:35:01 +0000142// Public interface to the Jump Threading pass
143FunctionPass *llvm::createJumpThreadingPass() { return new JumpThreading(); }
144
145/// runOnFunction - Top level algorithm.
146///
147bool JumpThreading::runOnFunction(Function &F) {
David Greenefe7fe662010-01-05 01:27:19 +0000148 DEBUG(dbgs() << "Jump threading on function '" << F.getName() << "'\n");
Dan Gohman02a436c2009-07-24 18:13:53 +0000149 TD = getAnalysisIfAvailable<TargetData>();
Owen Andersonc809d902010-09-14 20:57:41 +0000150 LVI = &getAnalysis<LazyValueInfo>();
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000151
Mike Stumpfe095f32009-05-04 18:40:41 +0000152 FindLoopHeaders(F);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000153
Benjamin Kramer66b581e2010-01-07 13:50:07 +0000154 bool Changed, EverChanged = false;
155 do {
156 Changed = false;
Chris Lattner421fa9e2008-12-03 07:48:08 +0000157 for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
158 BasicBlock *BB = I;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000159 // Thread all of the branches we can over this block.
Chris Lattner421fa9e2008-12-03 07:48:08 +0000160 while (ProcessBlock(BB))
Chris Lattnerbd3401f2008-04-20 22:39:42 +0000161 Changed = true;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000162
Chris Lattner421fa9e2008-12-03 07:48:08 +0000163 ++I;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000164
Chris Lattner421fa9e2008-12-03 07:48:08 +0000165 // If the block is trivially dead, zap it. This eliminates the successor
166 // edges which simplifies the CFG.
167 if (pred_begin(BB) == pred_end(BB) &&
Chris Lattner20fa76e2008-12-08 22:44:07 +0000168 BB != &BB->getParent()->getEntryBlock()) {
David Greenefe7fe662010-01-05 01:27:19 +0000169 DEBUG(dbgs() << " JT: Deleting dead block '" << BB->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +0000170 << "' with terminator: " << *BB->getTerminator() << '\n');
Mike Stumpfe095f32009-05-04 18:40:41 +0000171 LoopHeaders.erase(BB);
Owen Andersonc809d902010-09-14 20:57:41 +0000172 LVI->eraseBlock(BB);
Chris Lattner421fa9e2008-12-03 07:48:08 +0000173 DeleteDeadBlock(BB);
174 Changed = true;
Chris Lattnerf3183f62009-11-10 21:40:01 +0000175 } else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
176 // Can't thread an unconditional jump, but if the block is "almost
177 // empty", we can replace uses of it with uses of the successor and make
178 // this dead.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000179 if (BI->isUnconditional() &&
Chris Lattnerf3183f62009-11-10 21:40:01 +0000180 BB != &BB->getParent()->getEntryBlock()) {
181 BasicBlock::iterator BBI = BB->getFirstNonPHI();
182 // Ignore dbg intrinsics.
183 while (isa<DbgInfoIntrinsic>(BBI))
184 ++BBI;
185 // If the terminator is the only non-phi instruction, try to nuke it.
186 if (BBI->isTerminator()) {
Chris Lattner6f84a5f2009-11-10 21:45:09 +0000187 // Since TryToSimplifyUncondBranchFromEmptyBlock may delete the
188 // block, we have to make sure it isn't in the LoopHeaders set. We
Chris Lattner46875c02009-12-01 06:04:43 +0000189 // reinsert afterward if needed.
Chris Lattner6f84a5f2009-11-10 21:45:09 +0000190 bool ErasedFromLoopHeaders = LoopHeaders.erase(BB);
Chris Lattner46875c02009-12-01 06:04:43 +0000191 BasicBlock *Succ = BI->getSuccessor(0);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000192
Owen Anderson00ac77e2010-08-18 18:39:01 +0000193 // FIXME: It is always conservatively correct to drop the info
194 // for a block even if it doesn't get erased. This isn't totally
195 // awesome, but it allows us to use AssertingVH to prevent nasty
196 // dangling pointer issues within LazyValueInfo.
Owen Andersonc809d902010-09-14 20:57:41 +0000197 LVI->eraseBlock(BB);
Chris Lattner46875c02009-12-01 06:04:43 +0000198 if (TryToSimplifyUncondBranchFromEmptyBlock(BB)) {
Chris Lattnerf3183f62009-11-10 21:40:01 +0000199 Changed = true;
Chris Lattner46875c02009-12-01 06:04:43 +0000200 // If we deleted BB and BB was the header of a loop, then the
201 // successor is now the header of the loop.
202 BB = Succ;
203 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000204
Chris Lattner46875c02009-12-01 06:04:43 +0000205 if (ErasedFromLoopHeaders)
Chris Lattnerf3183f62009-11-10 21:40:01 +0000206 LoopHeaders.insert(BB);
207 }
208 }
Chris Lattner421fa9e2008-12-03 07:48:08 +0000209 }
210 }
Chris Lattnerbd3401f2008-04-20 22:39:42 +0000211 EverChanged |= Changed;
Benjamin Kramer66b581e2010-01-07 13:50:07 +0000212 } while (Changed);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000213
Mike Stumpfe095f32009-05-04 18:40:41 +0000214 LoopHeaders.clear();
Chris Lattnerbd3401f2008-04-20 22:39:42 +0000215 return EverChanged;
Chris Lattner8383a7b2008-04-20 20:35:01 +0000216}
Chris Lattner177480b2008-04-20 21:13:06 +0000217
Chris Lattner78c552e2009-10-11 07:24:57 +0000218/// getJumpThreadDuplicationCost - Return the cost of duplicating this block to
219/// thread across it.
220static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB) {
221 /// Ignore PHI nodes, these will be flattened when duplication happens.
222 BasicBlock::const_iterator I = BB->getFirstNonPHI();
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000223
Chris Lattnerb14b88a2009-11-11 00:21:58 +0000224 // FIXME: THREADING will delete values that are just used to compute the
225 // branch, so they shouldn't count against the duplication cost.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000226
227
Chris Lattner78c552e2009-10-11 07:24:57 +0000228 // Sum up the cost of each instruction until we get to the terminator. Don't
229 // include the terminator because the copy won't include it.
230 unsigned Size = 0;
231 for (; !isa<TerminatorInst>(I); ++I) {
232 // Debugger intrinsics don't incur code size.
233 if (isa<DbgInfoIntrinsic>(I)) continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000234
Chris Lattner78c552e2009-10-11 07:24:57 +0000235 // If this is a pointer->pointer bitcast, it is free.
Duncan Sands1df98592010-02-16 11:11:14 +0000236 if (isa<BitCastInst>(I) && I->getType()->isPointerTy())
Chris Lattner78c552e2009-10-11 07:24:57 +0000237 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000238
Chris Lattner78c552e2009-10-11 07:24:57 +0000239 // All other instructions count for at least one unit.
240 ++Size;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000241
Chris Lattner78c552e2009-10-11 07:24:57 +0000242 // Calls are more expensive. If they are non-intrinsic calls, we model them
243 // as having cost of 4. If they are a non-vector intrinsic, we model them
244 // as having cost of 2 total, and if they are a vector intrinsic, we model
245 // them as having cost 1.
246 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
247 if (!isa<IntrinsicInst>(CI))
248 Size += 3;
Duncan Sands1df98592010-02-16 11:11:14 +0000249 else if (!CI->getType()->isVectorTy())
Chris Lattner78c552e2009-10-11 07:24:57 +0000250 Size += 1;
251 }
252 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000253
Chris Lattner78c552e2009-10-11 07:24:57 +0000254 // Threading through a switch statement is particularly profitable. If this
255 // block ends in a switch, decrease its cost to make it more likely to happen.
256 if (isa<SwitchInst>(I))
257 Size = Size > 6 ? Size-6 : 0;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000258
Frits van Bommel6033b342010-12-06 23:36:56 +0000259 // The same holds for indirect branches, but slightly more so.
260 if (isa<IndirectBrInst>(I))
261 Size = Size > 8 ? Size-8 : 0;
262
Chris Lattner78c552e2009-10-11 07:24:57 +0000263 return Size;
264}
265
Mike Stumpfe095f32009-05-04 18:40:41 +0000266/// FindLoopHeaders - We do not want jump threading to turn proper loop
267/// structures into irreducible loops. Doing this breaks up the loop nesting
268/// hierarchy and pessimizes later transformations. To prevent this from
269/// happening, we first have to find the loop headers. Here we approximate this
270/// by finding targets of backedges in the CFG.
271///
272/// Note that there definitely are cases when we want to allow threading of
273/// edges across a loop header. For example, threading a jump from outside the
274/// loop (the preheader) to an exit block of the loop is definitely profitable.
275/// It is also almost always profitable to thread backedges from within the loop
276/// to exit blocks, and is often profitable to thread backedges to other blocks
277/// within the loop (forming a nested loop). This simple analysis is not rich
278/// enough to track all of these properties and keep it up-to-date as the CFG
279/// mutates, so we don't allow any of these transformations.
280///
281void JumpThreading::FindLoopHeaders(Function &F) {
282 SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges;
283 FindFunctionBackedges(F, Edges);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000284
Mike Stumpfe095f32009-05-04 18:40:41 +0000285 for (unsigned i = 0, e = Edges.size(); i != e; ++i)
286 LoopHeaders.insert(const_cast<BasicBlock*>(Edges[i].second));
287}
288
Frits van Bommelea388f22010-12-05 19:06:41 +0000289/// getKnownConstant - Helper method to determine if we can thread over a
290/// terminator with the given value as its condition, and if so what value to
Frits van Bommel6033b342010-12-06 23:36:56 +0000291/// use for that. What kind of value this is depends on whether we want an
292/// integer or a block address, but an undef is always accepted.
Frits van Bommelea388f22010-12-05 19:06:41 +0000293/// Returns null if Val is null or not an appropriate constant.
Frits van Bommel6033b342010-12-06 23:36:56 +0000294static Constant *getKnownConstant(Value *Val, ConstantPreference Preference) {
Frits van Bommelea388f22010-12-05 19:06:41 +0000295 if (!Val)
296 return 0;
297
298 // Undef is "known" enough.
299 if (UndefValue *U = dyn_cast<UndefValue>(Val))
300 return U;
301
Frits van Bommel6033b342010-12-06 23:36:56 +0000302 if (Preference == WantBlockAddress)
303 return dyn_cast<BlockAddress>(Val->stripPointerCasts());
304
Frits van Bommelea388f22010-12-05 19:06:41 +0000305 return dyn_cast<ConstantInt>(Val);
306}
307
Chris Lattner5729d382009-11-07 08:05:03 +0000308/// ComputeValueKnownInPredecessors - Given a basic block BB and a value V, see
Frits van Bommel6033b342010-12-06 23:36:56 +0000309/// if we can infer that the value is a known ConstantInt/BlockAddress or undef
310/// in any of our predecessors. If so, return the known list of value and pred
311/// BB in the result vector.
Chris Lattner5729d382009-11-07 08:05:03 +0000312///
Chris Lattner5729d382009-11-07 08:05:03 +0000313/// This returns true if there were any known values.
314///
Chris Lattner5729d382009-11-07 08:05:03 +0000315bool JumpThreading::
Frits van Bommel6033b342010-12-06 23:36:56 +0000316ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
317 ConstantPreference Preference) {
Owen Anderson9ba35362010-08-31 19:24:27 +0000318 // This method walks up use-def chains recursively. Because of this, we could
319 // get into an infinite loop going around loops in the use-def chain. To
320 // prevent this, keep track of what (value, block) pairs we've already visited
321 // and terminate the search if we loop back to them
Owen Andersoncb211902010-08-31 07:36:34 +0000322 if (!RecursionSet.insert(std::make_pair(V, BB)).second)
323 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000324
Owen Anderson9ba35362010-08-31 19:24:27 +0000325 // An RAII help to remove this pair from the recursion set once the recursion
326 // stack pops back out again.
327 RecursionSetRemover remover(RecursionSet, std::make_pair(V, BB));
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000328
Frits van Bommelea388f22010-12-05 19:06:41 +0000329 // If V is a constant, then it is known in all predecessors.
Frits van Bommel6033b342010-12-06 23:36:56 +0000330 if (Constant *KC = getKnownConstant(V, Preference)) {
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000331 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Frits van Bommelea388f22010-12-05 19:06:41 +0000332 Result.push_back(std::make_pair(KC, *PI));
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000333
Chris Lattner5729d382009-11-07 08:05:03 +0000334 return true;
335 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000336
Chris Lattner5729d382009-11-07 08:05:03 +0000337 // If V is a non-instruction value, or an instruction in a different block,
338 // then it can't be derived from a PHI.
339 Instruction *I = dyn_cast<Instruction>(V);
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000340 if (I == 0 || I->getParent() != BB) {
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000341
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000342 // Okay, if this is a live-in value, see if it has a known value at the end
343 // of any of our predecessors.
344 //
345 // FIXME: This should be an edge property, not a block end property.
346 /// TODO: Per PR2563, we could infer value range information about a
347 /// predecessor based on its terminator.
348 //
Owen Andersonc809d902010-09-14 20:57:41 +0000349 // FIXME: change this to use the more-rich 'getPredicateOnEdge' method if
350 // "I" is a non-local compare-with-a-constant instruction. This would be
351 // able to handle value inequalities better, for example if the compare is
352 // "X < 4" and "X < 3" is known true but "X < 4" itself is not available.
353 // Perhaps getConstantOnEdge should be smart enough to do this?
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000354
Owen Andersonc809d902010-09-14 20:57:41 +0000355 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
356 BasicBlock *P = *PI;
357 // If the value is known by LazyValueInfo to be a constant in a
358 // predecessor, use that information to try to thread this block.
359 Constant *PredCst = LVI->getConstantOnEdge(V, P, BB);
Frits van Bommel6033b342010-12-06 23:36:56 +0000360 if (Constant *KC = getKnownConstant(PredCst, Preference))
Frits van Bommelea388f22010-12-05 19:06:41 +0000361 Result.push_back(std::make_pair(KC, P));
Owen Andersonc809d902010-09-14 20:57:41 +0000362 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000363
Owen Andersonc809d902010-09-14 20:57:41 +0000364 return !Result.empty();
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000365 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000366
Chris Lattner5729d382009-11-07 08:05:03 +0000367 /// If I is a PHI node, then we know the incoming values for any constants.
368 if (PHINode *PN = dyn_cast<PHINode>(I)) {
369 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
370 Value *InVal = PN->getIncomingValue(i);
Frits van Bommel6033b342010-12-06 23:36:56 +0000371 if (Constant *KC = getKnownConstant(InVal, Preference)) {
Frits van Bommelea388f22010-12-05 19:06:41 +0000372 Result.push_back(std::make_pair(KC, PN->getIncomingBlock(i)));
Owen Andersonc809d902010-09-14 20:57:41 +0000373 } else {
Owen Anderson62efd3b2010-08-26 17:40:24 +0000374 Constant *CI = LVI->getConstantOnEdge(InVal,
375 PN->getIncomingBlock(i), BB);
Frits van Bommel6033b342010-12-06 23:36:56 +0000376 if (Constant *KC = getKnownConstant(CI, Preference))
377 Result.push_back(std::make_pair(KC, PN->getIncomingBlock(i)));
Chris Lattner5729d382009-11-07 08:05:03 +0000378 }
379 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000380
Chris Lattner5729d382009-11-07 08:05:03 +0000381 return !Result.empty();
382 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000383
Frits van Bommelea388f22010-12-05 19:06:41 +0000384 PredValueInfoTy LHSVals, RHSVals;
Chris Lattner5729d382009-11-07 08:05:03 +0000385
386 // Handle some boolean conditions.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000387 if (I->getType()->getPrimitiveSizeInBits() == 1) {
Frits van Bommel6033b342010-12-06 23:36:56 +0000388 assert(Preference == WantInteger && "One-bit non-integer type?");
Chris Lattner5729d382009-11-07 08:05:03 +0000389 // X | true -> true
390 // X & false -> false
391 if (I->getOpcode() == Instruction::Or ||
392 I->getOpcode() == Instruction::And) {
Frits van Bommel6033b342010-12-06 23:36:56 +0000393 ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
394 WantInteger);
395 ComputeValueKnownInPredecessors(I->getOperand(1), BB, RHSVals,
396 WantInteger);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000397
Owen Anderson9ba35362010-08-31 19:24:27 +0000398 if (LHSVals.empty() && RHSVals.empty())
Chris Lattner5729d382009-11-07 08:05:03 +0000399 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000400
Chris Lattner5729d382009-11-07 08:05:03 +0000401 ConstantInt *InterestingVal;
402 if (I->getOpcode() == Instruction::Or)
403 InterestingVal = ConstantInt::getTrue(I->getContext());
404 else
405 InterestingVal = ConstantInt::getFalse(I->getContext());
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000406
Chris Lattner2fa7b48e2010-08-18 03:14:36 +0000407 SmallPtrSet<BasicBlock*, 4> LHSKnownBBs;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000408
Chris Lattner1e452652010-02-11 04:40:44 +0000409 // Scan for the sentinel. If we find an undef, force it to the
410 // interesting value: x|undef -> true and x&undef -> false.
Chris Lattner5729d382009-11-07 08:05:03 +0000411 for (unsigned i = 0, e = LHSVals.size(); i != e; ++i)
Frits van Bommelea388f22010-12-05 19:06:41 +0000412 if (LHSVals[i].first == InterestingVal ||
413 isa<UndefValue>(LHSVals[i].first)) {
Chris Lattner5729d382009-11-07 08:05:03 +0000414 Result.push_back(LHSVals[i]);
Chris Lattner1e452652010-02-11 04:40:44 +0000415 Result.back().first = InterestingVal;
Chris Lattner2fa7b48e2010-08-18 03:14:36 +0000416 LHSKnownBBs.insert(LHSVals[i].second);
Chris Lattner1e452652010-02-11 04:40:44 +0000417 }
Chris Lattner5729d382009-11-07 08:05:03 +0000418 for (unsigned i = 0, e = RHSVals.size(); i != e; ++i)
Frits van Bommelea388f22010-12-05 19:06:41 +0000419 if (RHSVals[i].first == InterestingVal ||
420 isa<UndefValue>(RHSVals[i].first)) {
Chris Lattner0a961442010-07-12 00:47:34 +0000421 // If we already inferred a value for this block on the LHS, don't
422 // re-add it.
Chris Lattner2fa7b48e2010-08-18 03:14:36 +0000423 if (!LHSKnownBBs.count(RHSVals[i].second)) {
Chris Lattner0a961442010-07-12 00:47:34 +0000424 Result.push_back(RHSVals[i]);
425 Result.back().first = InterestingVal;
426 }
Chris Lattner1e452652010-02-11 04:40:44 +0000427 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000428
Chris Lattner5729d382009-11-07 08:05:03 +0000429 return !Result.empty();
430 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000431
Chris Lattner055d0462009-11-10 22:39:16 +0000432 // Handle the NOT form of XOR.
433 if (I->getOpcode() == Instruction::Xor &&
434 isa<ConstantInt>(I->getOperand(1)) &&
435 cast<ConstantInt>(I->getOperand(1))->isOne()) {
Frits van Bommel6033b342010-12-06 23:36:56 +0000436 ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result,
437 WantInteger);
Owen Anderson9ba35362010-08-31 19:24:27 +0000438 if (Result.empty())
Chris Lattner055d0462009-11-10 22:39:16 +0000439 return false;
440
441 // Invert the known values.
442 for (unsigned i = 0, e = Result.size(); i != e; ++i)
Frits van Bommelea388f22010-12-05 19:06:41 +0000443 Result[i].first = ConstantExpr::getNot(Result[i].first);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000444
Chris Lattner055d0462009-11-10 22:39:16 +0000445 return true;
446 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000447
Owen Anderson62efd3b2010-08-26 17:40:24 +0000448 // Try to simplify some other binary operator values.
449 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
Frits van Bommel6033b342010-12-06 23:36:56 +0000450 assert(Preference != WantBlockAddress
451 && "A binary operator creating a block address?");
Owen Anderson0eb355a2010-08-31 20:26:04 +0000452 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
Frits van Bommelea388f22010-12-05 19:06:41 +0000453 PredValueInfoTy LHSVals;
Frits van Bommel6033b342010-12-06 23:36:56 +0000454 ComputeValueKnownInPredecessors(BO->getOperand(0), BB, LHSVals,
455 WantInteger);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000456
Owen Andersoncb211902010-08-31 07:36:34 +0000457 // Try to use constant folding to simplify the binary operator.
458 for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) {
Chris Lattner906a6752010-09-05 20:03:09 +0000459 Constant *V = LHSVals[i].first;
Owen Anderson0eb355a2010-08-31 20:26:04 +0000460 Constant *Folded = ConstantExpr::get(BO->getOpcode(), V, CI);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000461
Frits van Bommel6033b342010-12-06 23:36:56 +0000462 if (Constant *KC = getKnownConstant(Folded, WantInteger))
463 Result.push_back(std::make_pair(KC, LHSVals[i].second));
Owen Andersoncb211902010-08-31 07:36:34 +0000464 }
Owen Anderson62efd3b2010-08-26 17:40:24 +0000465 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000466
Owen Andersoncb211902010-08-31 07:36:34 +0000467 return !Result.empty();
Chris Lattner5729d382009-11-07 08:05:03 +0000468 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000469
Chris Lattner5729d382009-11-07 08:05:03 +0000470 // Handle compare with phi operand, where the PHI is defined in this block.
471 if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
Frits van Bommel6033b342010-12-06 23:36:56 +0000472 assert(Preference == WantInteger && "Compares only produce integers");
Chris Lattner5729d382009-11-07 08:05:03 +0000473 PHINode *PN = dyn_cast<PHINode>(Cmp->getOperand(0));
474 if (PN && PN->getParent() == BB) {
475 // We can do this simplification if any comparisons fold to true or false.
476 // See if any do.
477 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
478 BasicBlock *PredBB = PN->getIncomingBlock(i);
479 Value *LHS = PN->getIncomingValue(i);
480 Value *RHS = Cmp->getOperand(1)->DoPHITranslation(BB, PredBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000481
Chris Lattner2ad00bf2009-11-11 22:31:38 +0000482 Value *Res = SimplifyCmpInst(Cmp->getPredicate(), LHS, RHS, TD);
Chris Lattner66c04c42009-11-12 05:24:05 +0000483 if (Res == 0) {
Owen Andersonc809d902010-09-14 20:57:41 +0000484 if (!isa<Constant>(RHS))
Chris Lattner66c04c42009-11-12 05:24:05 +0000485 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000486
487 LazyValueInfo::Tristate
Chris Lattner66c04c42009-11-12 05:24:05 +0000488 ResT = LVI->getPredicateOnEdge(Cmp->getPredicate(), LHS,
489 cast<Constant>(RHS), PredBB, BB);
490 if (ResT == LazyValueInfo::Unknown)
491 continue;
492 Res = ConstantInt::get(Type::getInt1Ty(LHS->getContext()), ResT);
493 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000494
Frits van Bommel6033b342010-12-06 23:36:56 +0000495 if (Constant *KC = getKnownConstant(Res, WantInteger))
496 Result.push_back(std::make_pair(KC, PredBB));
Chris Lattner5729d382009-11-07 08:05:03 +0000497 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000498
Chris Lattner5729d382009-11-07 08:05:03 +0000499 return !Result.empty();
500 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000501
502
Chris Lattner2ad00bf2009-11-11 22:31:38 +0000503 // If comparing a live-in value against a constant, see if we know the
504 // live-in value on any predecessors.
Owen Andersonc809d902010-09-14 20:57:41 +0000505 if (isa<Constant>(Cmp->getOperand(1)) && Cmp->getType()->isIntegerTy()) {
Owen Anderson62efd3b2010-08-26 17:40:24 +0000506 if (!isa<Instruction>(Cmp->getOperand(0)) ||
Owen Anderson327ca7b2010-08-30 23:22:36 +0000507 cast<Instruction>(Cmp->getOperand(0))->getParent() != BB) {
Owen Anderson62efd3b2010-08-26 17:40:24 +0000508 Constant *RHSCst = cast<Constant>(Cmp->getOperand(1));
Gabor Greifee1f44f2010-07-12 14:10:24 +0000509
Owen Anderson62efd3b2010-08-26 17:40:24 +0000510 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB);PI != E; ++PI){
511 BasicBlock *P = *PI;
512 // If the value is known by LazyValueInfo to be a constant in a
513 // predecessor, use that information to try to thread this block.
514 LazyValueInfo::Tristate Res =
515 LVI->getPredicateOnEdge(Cmp->getPredicate(), Cmp->getOperand(0),
516 RHSCst, P, BB);
517 if (Res == LazyValueInfo::Unknown)
518 continue;
Chris Lattner0e0ff292009-11-12 04:37:50 +0000519
Owen Anderson62efd3b2010-08-26 17:40:24 +0000520 Constant *ResC = ConstantInt::get(Cmp->getType(), Res);
Frits van Bommelea388f22010-12-05 19:06:41 +0000521 Result.push_back(std::make_pair(ResC, P));
Owen Anderson62efd3b2010-08-26 17:40:24 +0000522 }
523
524 return !Result.empty();
Chris Lattner2ad00bf2009-11-11 22:31:38 +0000525 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000526
Owen Andersoncb211902010-08-31 07:36:34 +0000527 // Try to find a constant value for the LHS of a comparison,
Owen Anderson62efd3b2010-08-26 17:40:24 +0000528 // and evaluate it statically if we can.
Owen Anderson327ca7b2010-08-30 23:22:36 +0000529 if (Constant *CmpConst = dyn_cast<Constant>(Cmp->getOperand(1))) {
Frits van Bommelea388f22010-12-05 19:06:41 +0000530 PredValueInfoTy LHSVals;
Frits van Bommel6033b342010-12-06 23:36:56 +0000531 ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals,
532 WantInteger);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000533
Owen Anderson62efd3b2010-08-26 17:40:24 +0000534 for (unsigned i = 0, e = LHSVals.size(); i != e; ++i) {
Chris Lattner906a6752010-09-05 20:03:09 +0000535 Constant *V = LHSVals[i].first;
Owen Anderson0eb355a2010-08-31 20:26:04 +0000536 Constant *Folded = ConstantExpr::getCompare(Cmp->getPredicate(),
537 V, CmpConst);
Frits van Bommel6033b342010-12-06 23:36:56 +0000538 if (Constant *KC = getKnownConstant(Folded, WantInteger))
539 Result.push_back(std::make_pair(KC, LHSVals[i].second));
Owen Anderson62efd3b2010-08-26 17:40:24 +0000540 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000541
Owen Anderson62efd3b2010-08-26 17:40:24 +0000542 return !Result.empty();
543 }
Chris Lattner2ad00bf2009-11-11 22:31:38 +0000544 }
Chris Lattner5729d382009-11-07 08:05:03 +0000545 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000546
Owen Andersonc809d902010-09-14 20:57:41 +0000547 // If all else fails, see if LVI can figure out a constant value for us.
548 Constant *CI = LVI->getConstant(V, BB);
Frits van Bommel6033b342010-12-06 23:36:56 +0000549 if (Constant *KC = getKnownConstant(CI, Preference)) {
Owen Andersonc809d902010-09-14 20:57:41 +0000550 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Frits van Bommelea388f22010-12-05 19:06:41 +0000551 Result.push_back(std::make_pair(KC, *PI));
Owen Anderson62efd3b2010-08-26 17:40:24 +0000552 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000553
Owen Andersonc809d902010-09-14 20:57:41 +0000554 return !Result.empty();
Chris Lattner5729d382009-11-07 08:05:03 +0000555}
556
557
Chris Lattner6bf77502008-04-22 07:05:46 +0000558
Chris Lattnere33583b2009-10-11 04:18:15 +0000559/// GetBestDestForBranchOnUndef - If we determine that the specified block ends
560/// in an undefined jump, decide which block is best to revector to.
561///
562/// Since we can pick an arbitrary destination, we pick the successor with the
563/// fewest predecessors. This should reduce the in-degree of the others.
564///
565static unsigned GetBestDestForJumpOnUndef(BasicBlock *BB) {
566 TerminatorInst *BBTerm = BB->getTerminator();
567 unsigned MinSucc = 0;
568 BasicBlock *TestBB = BBTerm->getSuccessor(MinSucc);
569 // Compute the successor with the minimum number of predecessors.
570 unsigned MinNumPreds = std::distance(pred_begin(TestBB), pred_end(TestBB));
571 for (unsigned i = 1, e = BBTerm->getNumSuccessors(); i != e; ++i) {
572 TestBB = BBTerm->getSuccessor(i);
573 unsigned NumPreds = std::distance(pred_begin(TestBB), pred_end(TestBB));
574 if (NumPreds < MinNumPreds)
575 MinSucc = i;
576 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000577
Chris Lattnere33583b2009-10-11 04:18:15 +0000578 return MinSucc;
579}
580
Chris Lattnerc7bcbf62008-11-27 07:20:04 +0000581/// ProcessBlock - If there are any predecessors whose control can be threaded
Chris Lattner177480b2008-04-20 21:13:06 +0000582/// through to a successor, transform them now.
Chris Lattnerc7bcbf62008-11-27 07:20:04 +0000583bool JumpThreading::ProcessBlock(BasicBlock *BB) {
Chris Lattner8231fd12010-01-23 18:56:07 +0000584 // If the block is trivially dead, just return and let the caller nuke it.
585 // This simplifies other transformations.
586 if (pred_begin(BB) == pred_end(BB) &&
587 BB != &BB->getParent()->getEntryBlock())
588 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000589
Chris Lattner69e067f2008-11-27 05:07:53 +0000590 // If this block has a single predecessor, and if that pred has a single
591 // successor, merge the blocks. This encourages recursive jump threading
592 // because now the condition in this block can be threaded through
593 // predecessors of our predecessor block.
Chris Lattner5729d382009-11-07 08:05:03 +0000594 if (BasicBlock *SinglePred = BB->getSinglePredecessor()) {
Chris Lattnerf5102a02008-11-28 19:54:49 +0000595 if (SinglePred->getTerminator()->getNumSuccessors() == 1 &&
596 SinglePred != BB) {
Mike Stumpfe095f32009-05-04 18:40:41 +0000597 // If SinglePred was a loop header, BB becomes one.
598 if (LoopHeaders.erase(SinglePred))
599 LoopHeaders.insert(BB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000600
Chris Lattner3d86d242008-11-27 19:25:19 +0000601 // Remember if SinglePred was the entry block of the function. If so, we
602 // will need to move BB back to the entry position.
603 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
Owen Andersonc809d902010-09-14 20:57:41 +0000604 LVI->eraseBlock(SinglePred);
Chris Lattner69e067f2008-11-27 05:07:53 +0000605 MergeBasicBlockIntoOnlyPred(BB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000606
Chris Lattner3d86d242008-11-27 19:25:19 +0000607 if (isEntry && BB != &BB->getParent()->getEntryBlock())
608 BB->moveBefore(&BB->getParent()->getEntryBlock());
Chris Lattner69e067f2008-11-27 05:07:53 +0000609 return true;
610 }
Chris Lattner5729d382009-11-07 08:05:03 +0000611 }
612
Frits van Bommel6033b342010-12-06 23:36:56 +0000613 // What kind of constant we're looking for.
614 ConstantPreference Preference = WantInteger;
615
616 // Look to see if the terminator is a conditional branch, switch or indirect
617 // branch, if not we can't thread it.
Chris Lattner177480b2008-04-20 21:13:06 +0000618 Value *Condition;
Frits van Bommel6033b342010-12-06 23:36:56 +0000619 Instruction *Terminator = BB->getTerminator();
620 if (BranchInst *BI = dyn_cast<BranchInst>(Terminator)) {
Chris Lattnerbd3401f2008-04-20 22:39:42 +0000621 // Can't thread an unconditional jump.
622 if (BI->isUnconditional()) return false;
Chris Lattner177480b2008-04-20 21:13:06 +0000623 Condition = BI->getCondition();
Frits van Bommel6033b342010-12-06 23:36:56 +0000624 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(Terminator)) {
Chris Lattner177480b2008-04-20 21:13:06 +0000625 Condition = SI->getCondition();
Frits van Bommel6033b342010-12-06 23:36:56 +0000626 } else if (IndirectBrInst *IB = dyn_cast<IndirectBrInst>(Terminator)) {
627 Condition = IB->getAddress()->stripPointerCasts();
628 Preference = WantBlockAddress;
629 } else {
Chris Lattner177480b2008-04-20 21:13:06 +0000630 return false; // Must be an invoke.
Frits van Bommel6033b342010-12-06 23:36:56 +0000631 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000632
Chris Lattner421fa9e2008-12-03 07:48:08 +0000633 // If the terminator is branching on an undef, we can pick any of the
Chris Lattnere33583b2009-10-11 04:18:15 +0000634 // successors to branch to. Let GetBestDestForJumpOnUndef decide.
Chris Lattner421fa9e2008-12-03 07:48:08 +0000635 if (isa<UndefValue>(Condition)) {
Chris Lattnere33583b2009-10-11 04:18:15 +0000636 unsigned BestSucc = GetBestDestForJumpOnUndef(BB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000637
Chris Lattner421fa9e2008-12-03 07:48:08 +0000638 // Fold the branch/switch.
Chris Lattnere33583b2009-10-11 04:18:15 +0000639 TerminatorInst *BBTerm = BB->getTerminator();
Chris Lattner421fa9e2008-12-03 07:48:08 +0000640 for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) {
Chris Lattnere33583b2009-10-11 04:18:15 +0000641 if (i == BestSucc) continue;
Owen Anderson36c4deb2010-09-29 20:34:41 +0000642 BBTerm->getSuccessor(i)->removePredecessor(BB, true);
Chris Lattner421fa9e2008-12-03 07:48:08 +0000643 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000644
David Greenefe7fe662010-01-05 01:27:19 +0000645 DEBUG(dbgs() << " In block '" << BB->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +0000646 << "' folding undef terminator: " << *BBTerm << '\n');
Chris Lattnere33583b2009-10-11 04:18:15 +0000647 BranchInst::Create(BBTerm->getSuccessor(BestSucc), BBTerm);
Chris Lattner421fa9e2008-12-03 07:48:08 +0000648 BBTerm->eraseFromParent();
649 return true;
650 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000651
Frits van Bommelea388f22010-12-05 19:06:41 +0000652 // If the terminator of this block is branching on a constant, simplify the
653 // terminator to an unconditional branch. This can occur due to threading in
654 // other blocks.
Frits van Bommel6033b342010-12-06 23:36:56 +0000655 if (getKnownConstant(Condition, Preference)) {
Frits van Bommelea388f22010-12-05 19:06:41 +0000656 DEBUG(dbgs() << " In block '" << BB->getName()
657 << "' folding terminator: " << *BB->getTerminator() << '\n');
658 ++NumFolds;
659 ConstantFoldTerminator(BB);
660 return true;
661 }
662
Chris Lattner421fa9e2008-12-03 07:48:08 +0000663 Instruction *CondInst = dyn_cast<Instruction>(Condition);
664
Chris Lattner421fa9e2008-12-03 07:48:08 +0000665 // All the rest of our checks depend on the condition being an instruction.
Chris Lattner87e9f592009-11-12 01:41:34 +0000666 if (CondInst == 0) {
667 // FIXME: Unify this with code below.
Frits van Bommel6033b342010-12-06 23:36:56 +0000668 if (ProcessThreadableEdges(Condition, BB, Preference))
Chris Lattner87e9f592009-11-12 01:41:34 +0000669 return true;
Chris Lattner421fa9e2008-12-03 07:48:08 +0000670 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000671 }
672
673
Nick Lewycky9683f182009-06-19 04:56:29 +0000674 if (CmpInst *CondCmp = dyn_cast<CmpInst>(CondInst)) {
Owen Anderson660cab32010-08-27 17:12:29 +0000675 // For a comparison where the LHS is outside this block, it's possible
Owen Andersonfc2fb172010-08-27 20:32:56 +0000676 // that we've branched on it before. Used LVI to see if we can simplify
Owen Anderson660cab32010-08-27 17:12:29 +0000677 // the branch based on that.
678 BranchInst *CondBr = dyn_cast<BranchInst>(BB->getTerminator());
679 Constant *CondConst = dyn_cast<Constant>(CondCmp->getOperand(1));
Owen Andersonc1bdac62010-08-31 18:48:48 +0000680 pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
Owen Andersonc809d902010-09-14 20:57:41 +0000681 if (CondBr && CondConst && CondBr->isConditional() && PI != PE &&
Owen Anderson660cab32010-08-27 17:12:29 +0000682 (!isa<Instruction>(CondCmp->getOperand(0)) ||
683 cast<Instruction>(CondCmp->getOperand(0))->getParent() != BB)) {
684 // For predecessor edge, determine if the comparison is true or false
685 // on that edge. If they're all true or all false, we can simplify the
686 // branch.
687 // FIXME: We could handle mixed true/false by duplicating code.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000688 LazyValueInfo::Tristate Baseline =
Owen Andersonc1bdac62010-08-31 18:48:48 +0000689 LVI->getPredicateOnEdge(CondCmp->getPredicate(), CondCmp->getOperand(0),
690 CondConst, *PI, BB);
691 if (Baseline != LazyValueInfo::Unknown) {
692 // Check that all remaining incoming values match the first one.
693 while (++PI != PE) {
Chris Lattnerbdabacd2010-09-05 20:10:47 +0000694 LazyValueInfo::Tristate Ret =
695 LVI->getPredicateOnEdge(CondCmp->getPredicate(),
696 CondCmp->getOperand(0), CondConst, *PI, BB);
Owen Andersonc1bdac62010-08-31 18:48:48 +0000697 if (Ret != Baseline) break;
698 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000699
Owen Andersonc1bdac62010-08-31 18:48:48 +0000700 // If we terminated early, then one of the values didn't match.
701 if (PI == PE) {
702 unsigned ToRemove = Baseline == LazyValueInfo::True ? 1 : 0;
703 unsigned ToKeep = Baseline == LazyValueInfo::True ? 0 : 1;
Owen Anderson36c4deb2010-09-29 20:34:41 +0000704 CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
Owen Andersonc1bdac62010-08-31 18:48:48 +0000705 BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
706 CondBr->eraseFromParent();
707 return true;
708 }
Owen Anderson660cab32010-08-27 17:12:29 +0000709 }
710 }
Nick Lewycky9683f182009-06-19 04:56:29 +0000711 }
Chris Lattner69e067f2008-11-27 05:07:53 +0000712
713 // Check for some cases that are worth simplifying. Right now we want to look
714 // for loads that are used by a switch or by the condition for the branch. If
715 // we see one, check to see if it's partially redundant. If so, insert a PHI
716 // which can then be used to thread the values.
717 //
Chris Lattner421fa9e2008-12-03 07:48:08 +0000718 Value *SimplifyValue = CondInst;
Chris Lattner69e067f2008-11-27 05:07:53 +0000719 if (CmpInst *CondCmp = dyn_cast<CmpInst>(SimplifyValue))
720 if (isa<Constant>(CondCmp->getOperand(1)))
721 SimplifyValue = CondCmp->getOperand(0);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000722
Chris Lattner4e447eb2009-11-15 19:58:31 +0000723 // TODO: There are other places where load PRE would be profitable, such as
724 // more complex comparisons.
Chris Lattner69e067f2008-11-27 05:07:53 +0000725 if (LoadInst *LI = dyn_cast<LoadInst>(SimplifyValue))
726 if (SimplifyPartiallyRedundantLoad(LI))
727 return true;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000728
729
Chris Lattner5729d382009-11-07 08:05:03 +0000730 // Handle a variety of cases where we are branching on something derived from
731 // a PHI node in the current block. If we can prove that any predecessors
732 // compute a predictable value based on a PHI node, thread those predecessors.
733 //
Frits van Bommel6033b342010-12-06 23:36:56 +0000734 if (ProcessThreadableEdges(CondInst, BB, Preference))
Chris Lattnercc4d3b22009-11-11 02:08:33 +0000735 return true;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000736
Chris Lattner77beb472010-01-11 23:41:09 +0000737 // If this is an otherwise-unfoldable branch on a phi node in the current
738 // block, see if we can simplify.
739 if (PHINode *PN = dyn_cast<PHINode>(CondInst))
740 if (PN->getParent() == BB && isa<BranchInst>(BB->getTerminator()))
741 return ProcessBranchOnPHI(PN);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000742
743
Chris Lattner2249a0b2010-01-12 02:07:17 +0000744 // If this is an otherwise-unfoldable branch on a XOR, see if we can simplify.
745 if (CondInst->getOpcode() == Instruction::Xor &&
746 CondInst->getParent() == BB && isa<BranchInst>(BB->getTerminator()))
747 return ProcessBranchOnXOR(cast<BinaryOperator>(CondInst));
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000748
749
Chris Lattner69e067f2008-11-27 05:07:53 +0000750 // TODO: If we have: "br (X > 0)" and we have a predecessor where we know
Chris Lattner77beb472010-01-11 23:41:09 +0000751 // "(X == 4)", thread through this block.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000752
Chris Lattnerd38c14e2008-04-22 06:36:15 +0000753 return false;
754}
755
Chris Lattner421fa9e2008-12-03 07:48:08 +0000756/// ProcessBranchOnDuplicateCond - We found a block and a predecessor of that
757/// block that jump on exactly the same condition. This means that we almost
758/// always know the direction of the edge in the DESTBB:
759/// PREDBB:
760/// br COND, DESTBB, BBY
761/// DESTBB:
762/// br COND, BBZ, BBW
763///
764/// If DESTBB has multiple predecessors, we can't just constant fold the branch
765/// in DESTBB, we have to thread over it.
766bool JumpThreading::ProcessBranchOnDuplicateCond(BasicBlock *PredBB,
767 BasicBlock *BB) {
768 BranchInst *PredBI = cast<BranchInst>(PredBB->getTerminator());
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000769
Chris Lattner421fa9e2008-12-03 07:48:08 +0000770 // If both successors of PredBB go to DESTBB, we don't know anything. We can
771 // fold the branch to an unconditional one, which allows other recursive
772 // simplifications.
773 bool BranchDir;
774 if (PredBI->getSuccessor(1) != BB)
775 BranchDir = true;
776 else if (PredBI->getSuccessor(0) != BB)
777 BranchDir = false;
778 else {
David Greenefe7fe662010-01-05 01:27:19 +0000779 DEBUG(dbgs() << " In block '" << PredBB->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +0000780 << "' folding terminator: " << *PredBB->getTerminator() << '\n');
Chris Lattner421fa9e2008-12-03 07:48:08 +0000781 ++NumFolds;
782 ConstantFoldTerminator(PredBB);
783 return true;
784 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000785
Chris Lattner421fa9e2008-12-03 07:48:08 +0000786 BranchInst *DestBI = cast<BranchInst>(BB->getTerminator());
787
788 // If the dest block has one predecessor, just fix the branch condition to a
789 // constant and fold it.
790 if (BB->getSinglePredecessor()) {
David Greenefe7fe662010-01-05 01:27:19 +0000791 DEBUG(dbgs() << " In block '" << BB->getName()
Daniel Dunbar93b67e42009-07-26 07:49:05 +0000792 << "' folding condition to '" << BranchDir << "': "
Chris Lattner78c552e2009-10-11 07:24:57 +0000793 << *BB->getTerminator() << '\n');
Chris Lattner421fa9e2008-12-03 07:48:08 +0000794 ++NumFolds;
Chris Lattner5a06cf62009-10-11 18:39:58 +0000795 Value *OldCond = DestBI->getCondition();
Owen Anderson1d0be152009-08-13 21:58:54 +0000796 DestBI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()),
797 BranchDir));
Chris Lattner6f285d22010-04-10 18:26:57 +0000798 // Delete dead instructions before we fold the branch. Folding the branch
799 // can eliminate edges from the CFG which can end up deleting OldCond.
Chris Lattner5a06cf62009-10-11 18:39:58 +0000800 RecursivelyDeleteTriviallyDeadInstructions(OldCond);
Chris Lattner6f285d22010-04-10 18:26:57 +0000801 ConstantFoldTerminator(BB);
Chris Lattner421fa9e2008-12-03 07:48:08 +0000802 return true;
803 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000804
805
Chris Lattner421fa9e2008-12-03 07:48:08 +0000806 // Next, figure out which successor we are threading to.
807 BasicBlock *SuccBB = DestBI->getSuccessor(!BranchDir);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000808
Chris Lattner5729d382009-11-07 08:05:03 +0000809 SmallVector<BasicBlock*, 2> Preds;
810 Preds.push_back(PredBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000811
Mike Stumpfe095f32009-05-04 18:40:41 +0000812 // Ok, try to thread it!
Chris Lattner5729d382009-11-07 08:05:03 +0000813 return ThreadEdge(BB, Preds, SuccBB);
Chris Lattner421fa9e2008-12-03 07:48:08 +0000814}
815
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000816/// ProcessSwitchOnDuplicateCond - We found a block and a predecessor of that
817/// block that switch on exactly the same condition. This means that we almost
818/// always know the direction of the edge in the DESTBB:
819/// PREDBB:
820/// switch COND [... DESTBB, BBY ... ]
821/// DESTBB:
822/// switch COND [... BBZ, BBW ]
823///
824/// Optimizing switches like this is very important, because simplifycfg builds
825/// switches out of repeated 'if' conditions.
826bool JumpThreading::ProcessSwitchOnDuplicateCond(BasicBlock *PredBB,
827 BasicBlock *DestBB) {
Chris Lattner2c7ed112009-01-19 21:20:34 +0000828 // Can't thread edge to self.
829 if (PredBB == DestBB)
830 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000831
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000832 SwitchInst *PredSI = cast<SwitchInst>(PredBB->getTerminator());
833 SwitchInst *DestSI = cast<SwitchInst>(DestBB->getTerminator());
834
835 // There are a variety of optimizations that we can potentially do on these
836 // blocks: we order them from most to least preferable.
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000837
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000838 // If DESTBB *just* contains the switch, then we can forward edges from PREDBB
839 // directly to their destination. This does not introduce *any* code size
Dale Johannesen6b233392009-03-17 00:38:24 +0000840 // growth. Skip debug info first.
841 BasicBlock::iterator BBI = DestBB->begin();
842 while (isa<DbgInfoIntrinsic>(BBI))
843 BBI++;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000844
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000845 // FIXME: Thread if it just contains a PHI.
Dale Johannesen6b233392009-03-17 00:38:24 +0000846 if (isa<SwitchInst>(BBI)) {
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000847 bool MadeChange = false;
848 // Ignore the default edge for now.
849 for (unsigned i = 1, e = DestSI->getNumSuccessors(); i != e; ++i) {
850 ConstantInt *DestVal = DestSI->getCaseValue(i);
851 BasicBlock *DestSucc = DestSI->getSuccessor(i);
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000852
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000853 // Okay, DestSI has a case for 'DestVal' that goes to 'DestSucc'. See if
854 // PredSI has an explicit case for it. If so, forward. If it is covered
855 // by the default case, we can't update PredSI.
856 unsigned PredCase = PredSI->findCaseValue(DestVal);
857 if (PredCase == 0) continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000858
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000859 // If PredSI doesn't go to DestBB on this value, then it won't reach the
860 // case on this condition.
861 if (PredSI->getSuccessor(PredCase) != DestBB &&
862 DestSI->getSuccessor(i) != DestBB)
863 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000864
Chris Lattner08bc2702009-12-06 17:17:23 +0000865 // Do not forward this if it already goes to this destination, this would
866 // be an infinite loop.
867 if (PredSI->getSuccessor(PredCase) == DestSucc)
868 continue;
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000869
870 // Otherwise, we're safe to make the change. Make sure that the edge from
871 // DestSI to DestSucc is not critical and has no PHI nodes.
David Greenefe7fe662010-01-05 01:27:19 +0000872 DEBUG(dbgs() << "FORWARDING EDGE " << *DestVal << " FROM: " << *PredSI);
873 DEBUG(dbgs() << "THROUGH: " << *DestSI);
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000874
875 // If the destination has PHI nodes, just split the edge for updating
876 // simplicity.
877 if (isa<PHINode>(DestSucc->begin()) && !DestSucc->getSinglePredecessor()){
878 SplitCriticalEdge(DestSI, i, this);
879 DestSucc = DestSI->getSuccessor(i);
880 }
881 FoldSingleEntryPHINodes(DestSucc);
882 PredSI->setSuccessor(PredCase, DestSucc);
883 MadeChange = true;
884 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000885
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000886 if (MadeChange)
887 return true;
888 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000889
Chris Lattner3cda3cd2008-12-04 06:31:07 +0000890 return false;
891}
892
893
Chris Lattner69e067f2008-11-27 05:07:53 +0000894/// SimplifyPartiallyRedundantLoad - If LI is an obviously partially redundant
895/// load instruction, eliminate it by replacing it with a PHI node. This is an
896/// important optimization that encourages jump threading, and needs to be run
897/// interlaced with other jump threading tasks.
898bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
899 // Don't hack volatile loads.
900 if (LI->isVolatile()) return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000901
Chris Lattner69e067f2008-11-27 05:07:53 +0000902 // If the load is defined in a block with exactly one predecessor, it can't be
903 // partially redundant.
904 BasicBlock *LoadBB = LI->getParent();
905 if (LoadBB->getSinglePredecessor())
906 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000907
Chris Lattner69e067f2008-11-27 05:07:53 +0000908 Value *LoadedPtr = LI->getOperand(0);
909
910 // If the loaded operand is defined in the LoadBB, it can't be available.
Chris Lattner4e447eb2009-11-15 19:58:31 +0000911 // TODO: Could do simple PHI translation, that would be fun :)
Chris Lattner69e067f2008-11-27 05:07:53 +0000912 if (Instruction *PtrOp = dyn_cast<Instruction>(LoadedPtr))
913 if (PtrOp->getParent() == LoadBB)
914 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000915
Chris Lattner69e067f2008-11-27 05:07:53 +0000916 // Scan a few instructions up from the load, to see if it is obviously live at
917 // the entry to its block.
918 BasicBlock::iterator BBIt = LI;
919
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000920 if (Value *AvailableVal =
Chris Lattner4e447eb2009-11-15 19:58:31 +0000921 FindAvailableLoadedValue(LoadedPtr, LoadBB, BBIt, 6)) {
Chris Lattner69e067f2008-11-27 05:07:53 +0000922 // If the value if the load is locally available within the block, just use
923 // it. This frequently occurs for reg2mem'd allocas.
924 //cerr << "LOAD ELIMINATED:\n" << *BBIt << *LI << "\n";
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000925
Chris Lattner2a99b482009-01-09 06:08:12 +0000926 // If the returned value is the load itself, replace with an undef. This can
927 // only happen in dead loops.
Owen Anderson9e9a0d52009-07-30 23:03:37 +0000928 if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
Chris Lattner69e067f2008-11-27 05:07:53 +0000929 LI->replaceAllUsesWith(AvailableVal);
930 LI->eraseFromParent();
931 return true;
932 }
933
934 // Otherwise, if we scanned the whole block and got to the top of the block,
935 // we know the block is locally transparent to the load. If not, something
936 // might clobber its value.
937 if (BBIt != LoadBB->begin())
938 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000939
940
Chris Lattner69e067f2008-11-27 05:07:53 +0000941 SmallPtrSet<BasicBlock*, 8> PredsScanned;
942 typedef SmallVector<std::pair<BasicBlock*, Value*>, 8> AvailablePredsTy;
943 AvailablePredsTy AvailablePreds;
944 BasicBlock *OneUnavailablePred = 0;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000945
Chris Lattner69e067f2008-11-27 05:07:53 +0000946 // If we got here, the loaded value is transparent through to the start of the
947 // block. Check to see if it is available in any of the predecessor blocks.
948 for (pred_iterator PI = pred_begin(LoadBB), PE = pred_end(LoadBB);
949 PI != PE; ++PI) {
950 BasicBlock *PredBB = *PI;
951
952 // If we already scanned this predecessor, skip it.
953 if (!PredsScanned.insert(PredBB))
954 continue;
955
956 // Scan the predecessor to see if the value is available in the pred.
957 BBIt = PredBB->end();
Chris Lattner52c95852008-11-27 08:10:05 +0000958 Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6);
Chris Lattner69e067f2008-11-27 05:07:53 +0000959 if (!PredAvailable) {
960 OneUnavailablePred = PredBB;
961 continue;
962 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000963
Chris Lattner69e067f2008-11-27 05:07:53 +0000964 // If so, this load is partially redundant. Remember this info so that we
965 // can create a PHI node.
966 AvailablePreds.push_back(std::make_pair(PredBB, PredAvailable));
967 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000968
Chris Lattner69e067f2008-11-27 05:07:53 +0000969 // If the loaded value isn't available in any predecessor, it isn't partially
970 // redundant.
971 if (AvailablePreds.empty()) return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000972
Chris Lattner69e067f2008-11-27 05:07:53 +0000973 // Okay, the loaded value is available in at least one (and maybe all!)
974 // predecessors. If the value is unavailable in more than one unique
975 // predecessor, we want to insert a merge block for those common predecessors.
976 // This ensures that we only have to insert one reload, thus not increasing
977 // code size.
978 BasicBlock *UnavailablePred = 0;
Frits van Bommel6f9a8302010-12-05 19:02:47 +0000979
Chris Lattner69e067f2008-11-27 05:07:53 +0000980 // If there is exactly one predecessor where the value is unavailable, the
981 // already computed 'OneUnavailablePred' block is it. If it ends in an
982 // unconditional branch, we know that it isn't a critical edge.
983 if (PredsScanned.size() == AvailablePreds.size()+1 &&
984 OneUnavailablePred->getTerminator()->getNumSuccessors() == 1) {
985 UnavailablePred = OneUnavailablePred;
986 } else if (PredsScanned.size() != AvailablePreds.size()) {
987 // Otherwise, we had multiple unavailable predecessors or we had a critical
988 // edge from the one.
989 SmallVector<BasicBlock*, 8> PredsToSplit;
990 SmallPtrSet<BasicBlock*, 8> AvailablePredSet;
991
992 for (unsigned i = 0, e = AvailablePreds.size(); i != e; ++i)
993 AvailablePredSet.insert(AvailablePreds[i].first);
994
995 // Add all the unavailable predecessors to the PredsToSplit list.
996 for (pred_iterator PI = pred_begin(LoadBB), PE = pred_end(LoadBB);
Chris Lattnere58867e2010-06-14 19:45:43 +0000997 PI != PE; ++PI) {
Gabor Greifee1f44f2010-07-12 14:10:24 +0000998 BasicBlock *P = *PI;
Chris Lattnere58867e2010-06-14 19:45:43 +0000999 // If the predecessor is an indirect goto, we can't split the edge.
Gabor Greifee1f44f2010-07-12 14:10:24 +00001000 if (isa<IndirectBrInst>(P->getTerminator()))
Chris Lattnere58867e2010-06-14 19:45:43 +00001001 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001002
Gabor Greifee1f44f2010-07-12 14:10:24 +00001003 if (!AvailablePredSet.count(P))
1004 PredsToSplit.push_back(P);
Chris Lattnere58867e2010-06-14 19:45:43 +00001005 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001006
Chris Lattner69e067f2008-11-27 05:07:53 +00001007 // Split them out to their own block.
1008 UnavailablePred =
1009 SplitBlockPredecessors(LoadBB, &PredsToSplit[0], PredsToSplit.size(),
Chris Lattner4e447eb2009-11-15 19:58:31 +00001010 "thread-pre-split", this);
Chris Lattner69e067f2008-11-27 05:07:53 +00001011 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001012
Chris Lattner69e067f2008-11-27 05:07:53 +00001013 // If the value isn't available in all predecessors, then there will be
1014 // exactly one where it isn't available. Insert a load on that edge and add
1015 // it to the AvailablePreds list.
1016 if (UnavailablePred) {
1017 assert(UnavailablePred->getTerminator()->getNumSuccessors() == 1 &&
1018 "Can't handle critical edge here!");
Chris Lattner4e447eb2009-11-15 19:58:31 +00001019 Value *NewVal = new LoadInst(LoadedPtr, LI->getName()+".pr", false,
1020 LI->getAlignment(),
Chris Lattner69e067f2008-11-27 05:07:53 +00001021 UnavailablePred->getTerminator());
1022 AvailablePreds.push_back(std::make_pair(UnavailablePred, NewVal));
1023 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001024
Chris Lattner69e067f2008-11-27 05:07:53 +00001025 // Now we know that each predecessor of this block has a value in
1026 // AvailablePreds, sort them for efficient access as we're walking the preds.
Chris Lattnera3522002008-12-01 06:52:57 +00001027 array_pod_sort(AvailablePreds.begin(), AvailablePreds.end());
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001028
Chris Lattner69e067f2008-11-27 05:07:53 +00001029 // Create a PHI node at the start of the block for the PRE'd load value.
1030 PHINode *PN = PHINode::Create(LI->getType(), "", LoadBB->begin());
1031 PN->takeName(LI);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001032
Chris Lattner69e067f2008-11-27 05:07:53 +00001033 // Insert new entries into the PHI for each predecessor. A single block may
1034 // have multiple entries here.
1035 for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB); PI != E;
1036 ++PI) {
Gabor Greifee1f44f2010-07-12 14:10:24 +00001037 BasicBlock *P = *PI;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001038 AvailablePredsTy::iterator I =
Chris Lattner69e067f2008-11-27 05:07:53 +00001039 std::lower_bound(AvailablePreds.begin(), AvailablePreds.end(),
Gabor Greifee1f44f2010-07-12 14:10:24 +00001040 std::make_pair(P, (Value*)0));
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001041
Gabor Greifee1f44f2010-07-12 14:10:24 +00001042 assert(I != AvailablePreds.end() && I->first == P &&
Chris Lattner69e067f2008-11-27 05:07:53 +00001043 "Didn't find entry for predecessor!");
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001044
Chris Lattner69e067f2008-11-27 05:07:53 +00001045 PN->addIncoming(I->second, I->first);
1046 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001047
Chris Lattner69e067f2008-11-27 05:07:53 +00001048 //cerr << "PRE: " << *LI << *PN << "\n";
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001049
Chris Lattner69e067f2008-11-27 05:07:53 +00001050 LI->replaceAllUsesWith(PN);
1051 LI->eraseFromParent();
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001052
Chris Lattner69e067f2008-11-27 05:07:53 +00001053 return true;
1054}
1055
Chris Lattner5729d382009-11-07 08:05:03 +00001056/// FindMostPopularDest - The specified list contains multiple possible
1057/// threadable destinations. Pick the one that occurs the most frequently in
1058/// the list.
1059static BasicBlock *
1060FindMostPopularDest(BasicBlock *BB,
1061 const SmallVectorImpl<std::pair<BasicBlock*,
1062 BasicBlock*> > &PredToDestList) {
1063 assert(!PredToDestList.empty());
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001064
Chris Lattner5729d382009-11-07 08:05:03 +00001065 // Determine popularity. If there are multiple possible destinations, we
1066 // explicitly choose to ignore 'undef' destinations. We prefer to thread
1067 // blocks with known and real destinations to threading undef. We'll handle
1068 // them later if interesting.
1069 DenseMap<BasicBlock*, unsigned> DestPopularity;
1070 for (unsigned i = 0, e = PredToDestList.size(); i != e; ++i)
1071 if (PredToDestList[i].second)
1072 DestPopularity[PredToDestList[i].second]++;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001073
Chris Lattner5729d382009-11-07 08:05:03 +00001074 // Find the most popular dest.
1075 DenseMap<BasicBlock*, unsigned>::iterator DPI = DestPopularity.begin();
1076 BasicBlock *MostPopularDest = DPI->first;
1077 unsigned Popularity = DPI->second;
1078 SmallVector<BasicBlock*, 4> SamePopularity;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001079
Chris Lattner5729d382009-11-07 08:05:03 +00001080 for (++DPI; DPI != DestPopularity.end(); ++DPI) {
1081 // If the popularity of this entry isn't higher than the popularity we've
1082 // seen so far, ignore it.
1083 if (DPI->second < Popularity)
1084 ; // ignore.
1085 else if (DPI->second == Popularity) {
1086 // If it is the same as what we've seen so far, keep track of it.
1087 SamePopularity.push_back(DPI->first);
1088 } else {
1089 // If it is more popular, remember it.
1090 SamePopularity.clear();
1091 MostPopularDest = DPI->first;
1092 Popularity = DPI->second;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001093 }
Chris Lattner5729d382009-11-07 08:05:03 +00001094 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001095
Chris Lattner5729d382009-11-07 08:05:03 +00001096 // Okay, now we know the most popular destination. If there is more than
1097 // destination, we need to determine one. This is arbitrary, but we need
1098 // to make a deterministic decision. Pick the first one that appears in the
1099 // successor list.
1100 if (!SamePopularity.empty()) {
1101 SamePopularity.push_back(MostPopularDest);
1102 TerminatorInst *TI = BB->getTerminator();
1103 for (unsigned i = 0; ; ++i) {
1104 assert(i != TI->getNumSuccessors() && "Didn't find any successor!");
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001105
Chris Lattner5729d382009-11-07 08:05:03 +00001106 if (std::find(SamePopularity.begin(), SamePopularity.end(),
1107 TI->getSuccessor(i)) == SamePopularity.end())
1108 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001109
Chris Lattner5729d382009-11-07 08:05:03 +00001110 MostPopularDest = TI->getSuccessor(i);
1111 break;
1112 }
1113 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001114
Chris Lattner5729d382009-11-07 08:05:03 +00001115 // Okay, we have finally picked the most popular destination.
1116 return MostPopularDest;
1117}
1118
Frits van Bommel6033b342010-12-06 23:36:56 +00001119bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
1120 ConstantPreference Preference) {
Chris Lattner5729d382009-11-07 08:05:03 +00001121 // If threading this would thread across a loop header, don't even try to
1122 // thread the edge.
1123 if (LoopHeaders.count(BB))
1124 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001125
Frits van Bommelea388f22010-12-05 19:06:41 +00001126 PredValueInfoTy PredValues;
Frits van Bommel6033b342010-12-06 23:36:56 +00001127 if (!ComputeValueKnownInPredecessors(Cond, BB, PredValues, Preference))
Chris Lattner5729d382009-11-07 08:05:03 +00001128 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001129
Chris Lattner5729d382009-11-07 08:05:03 +00001130 assert(!PredValues.empty() &&
1131 "ComputeValueKnownInPredecessors returned true with no values");
1132
David Greenefe7fe662010-01-05 01:27:19 +00001133 DEBUG(dbgs() << "IN BB: " << *BB;
Chris Lattner5729d382009-11-07 08:05:03 +00001134 for (unsigned i = 0, e = PredValues.size(); i != e; ++i) {
Frits van Bommelea388f22010-12-05 19:06:41 +00001135 dbgs() << " BB '" << BB->getName() << "': FOUND condition = "
1136 << *PredValues[i].first
1137 << " for pred '" << PredValues[i].second->getName() << "'.\n";
Chris Lattner5729d382009-11-07 08:05:03 +00001138 });
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001139
Chris Lattner5729d382009-11-07 08:05:03 +00001140 // Decide what we want to thread through. Convert our list of known values to
1141 // a list of known destinations for each pred. This also discards duplicate
1142 // predecessors and keeps track of the undefined inputs (which are represented
Chris Lattnere7e63fe2009-11-09 00:41:49 +00001143 // as a null dest in the PredToDestList).
Chris Lattner5729d382009-11-07 08:05:03 +00001144 SmallPtrSet<BasicBlock*, 16> SeenPreds;
1145 SmallVector<std::pair<BasicBlock*, BasicBlock*>, 16> PredToDestList;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001146
Chris Lattner5729d382009-11-07 08:05:03 +00001147 BasicBlock *OnlyDest = 0;
1148 BasicBlock *MultipleDestSentinel = (BasicBlock*)(intptr_t)~0ULL;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001149
Chris Lattner5729d382009-11-07 08:05:03 +00001150 for (unsigned i = 0, e = PredValues.size(); i != e; ++i) {
1151 BasicBlock *Pred = PredValues[i].second;
1152 if (!SeenPreds.insert(Pred))
1153 continue; // Duplicate predecessor entry.
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001154
Chris Lattner5729d382009-11-07 08:05:03 +00001155 // If the predecessor ends with an indirect goto, we can't change its
1156 // destination.
1157 if (isa<IndirectBrInst>(Pred->getTerminator()))
1158 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001159
Frits van Bommelea388f22010-12-05 19:06:41 +00001160 Constant *Val = PredValues[i].first;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001161
Chris Lattner5729d382009-11-07 08:05:03 +00001162 BasicBlock *DestBB;
Frits van Bommelea388f22010-12-05 19:06:41 +00001163 if (isa<UndefValue>(Val))
Chris Lattner5729d382009-11-07 08:05:03 +00001164 DestBB = 0;
1165 else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
Frits van Bommelea388f22010-12-05 19:06:41 +00001166 DestBB = BI->getSuccessor(cast<ConstantInt>(Val)->isZero());
Frits van Bommel6033b342010-12-06 23:36:56 +00001167 else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator()))
Frits van Bommelea388f22010-12-05 19:06:41 +00001168 DestBB = SI->getSuccessor(SI->findCaseValue(cast<ConstantInt>(Val)));
Frits van Bommel6033b342010-12-06 23:36:56 +00001169 else {
1170 assert(isa<IndirectBrInst>(BB->getTerminator())
1171 && "Unexpected terminator");
1172 DestBB = cast<BlockAddress>(Val)->getBasicBlock();
Chris Lattner5729d382009-11-07 08:05:03 +00001173 }
1174
1175 // If we have exactly one destination, remember it for efficiency below.
1176 if (i == 0)
1177 OnlyDest = DestBB;
1178 else if (OnlyDest != DestBB)
1179 OnlyDest = MultipleDestSentinel;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001180
Chris Lattner5729d382009-11-07 08:05:03 +00001181 PredToDestList.push_back(std::make_pair(Pred, DestBB));
1182 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001183
Chris Lattner5729d382009-11-07 08:05:03 +00001184 // If all edges were unthreadable, we fail.
1185 if (PredToDestList.empty())
1186 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001187
Chris Lattner5729d382009-11-07 08:05:03 +00001188 // Determine which is the most common successor. If we have many inputs and
1189 // this block is a switch, we want to start by threading the batch that goes
1190 // to the most popular destination first. If we only know about one
1191 // threadable destination (the common case) we can avoid this.
1192 BasicBlock *MostPopularDest = OnlyDest;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001193
Chris Lattner5729d382009-11-07 08:05:03 +00001194 if (MostPopularDest == MultipleDestSentinel)
1195 MostPopularDest = FindMostPopularDest(BB, PredToDestList);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001196
Chris Lattner5729d382009-11-07 08:05:03 +00001197 // Now that we know what the most popular destination is, factor all
1198 // predecessors that will jump to it into a single predecessor.
1199 SmallVector<BasicBlock*, 16> PredsToFactor;
1200 for (unsigned i = 0, e = PredToDestList.size(); i != e; ++i)
1201 if (PredToDestList[i].second == MostPopularDest) {
1202 BasicBlock *Pred = PredToDestList[i].first;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001203
Chris Lattner5729d382009-11-07 08:05:03 +00001204 // This predecessor may be a switch or something else that has multiple
1205 // edges to the block. Factor each of these edges by listing them
1206 // according to # occurrences in PredsToFactor.
1207 TerminatorInst *PredTI = Pred->getTerminator();
1208 for (unsigned i = 0, e = PredTI->getNumSuccessors(); i != e; ++i)
1209 if (PredTI->getSuccessor(i) == BB)
1210 PredsToFactor.push_back(Pred);
1211 }
1212
1213 // If the threadable edges are branching on an undefined value, we get to pick
1214 // the destination that these predecessors should get to.
1215 if (MostPopularDest == 0)
1216 MostPopularDest = BB->getTerminator()->
1217 getSuccessor(GetBestDestForJumpOnUndef(BB));
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001218
Chris Lattner5729d382009-11-07 08:05:03 +00001219 // Ok, try to thread it!
1220 return ThreadEdge(BB, PredsToFactor, MostPopularDest);
1221}
Chris Lattner69e067f2008-11-27 05:07:53 +00001222
Chris Lattner77beb472010-01-11 23:41:09 +00001223/// ProcessBranchOnPHI - We have an otherwise unthreadable conditional branch on
1224/// a PHI node in the current block. See if there are any simplifications we
1225/// can do based on inputs to the phi node.
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001226///
Chris Lattner77beb472010-01-11 23:41:09 +00001227bool JumpThreading::ProcessBranchOnPHI(PHINode *PN) {
Chris Lattner6b65f472009-10-11 04:40:21 +00001228 BasicBlock *BB = PN->getParent();
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001229
Chris Lattner2249a0b2010-01-12 02:07:17 +00001230 // TODO: We could make use of this to do it once for blocks with common PHI
1231 // values.
1232 SmallVector<BasicBlock*, 1> PredBBs;
1233 PredBBs.resize(1);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001234
Chris Lattner5729d382009-11-07 08:05:03 +00001235 // If any of the predecessor blocks end in an unconditional branch, we can
Chris Lattner77beb472010-01-11 23:41:09 +00001236 // *duplicate* the conditional branch into that block in order to further
1237 // encourage jump threading and to eliminate cases where we have branch on a
1238 // phi of an icmp (branch on icmp is much better).
Chris Lattner78c552e2009-10-11 07:24:57 +00001239 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1240 BasicBlock *PredBB = PN->getIncomingBlock(i);
1241 if (BranchInst *PredBr = dyn_cast<BranchInst>(PredBB->getTerminator()))
Chris Lattner2249a0b2010-01-12 02:07:17 +00001242 if (PredBr->isUnconditional()) {
1243 PredBBs[0] = PredBB;
1244 // Try to duplicate BB into PredBB.
1245 if (DuplicateCondBranchOnPHIIntoPred(BB, PredBBs))
1246 return true;
1247 }
Chris Lattner78c552e2009-10-11 07:24:57 +00001248 }
1249
Chris Lattner6b65f472009-10-11 04:40:21 +00001250 return false;
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001251}
1252
Chris Lattner2249a0b2010-01-12 02:07:17 +00001253/// ProcessBranchOnXOR - We have an otherwise unthreadable conditional branch on
1254/// a xor instruction in the current block. See if there are any
1255/// simplifications we can do based on inputs to the xor.
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001256///
Chris Lattner2249a0b2010-01-12 02:07:17 +00001257bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) {
1258 BasicBlock *BB = BO->getParent();
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001259
Chris Lattner2249a0b2010-01-12 02:07:17 +00001260 // If either the LHS or RHS of the xor is a constant, don't do this
1261 // optimization.
1262 if (isa<ConstantInt>(BO->getOperand(0)) ||
1263 isa<ConstantInt>(BO->getOperand(1)))
1264 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001265
Chris Lattner2dd76572010-01-23 19:16:25 +00001266 // If the first instruction in BB isn't a phi, we won't be able to infer
1267 // anything special about any particular predecessor.
1268 if (!isa<PHINode>(BB->front()))
1269 return false;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001270
Chris Lattner2249a0b2010-01-12 02:07:17 +00001271 // If we have a xor as the branch input to this block, and we know that the
1272 // LHS or RHS of the xor in any predecessor is true/false, then we can clone
1273 // the condition into the predecessor and fix that value to true, saving some
1274 // logical ops on that path and encouraging other paths to simplify.
1275 //
1276 // This copies something like this:
1277 //
1278 // BB:
1279 // %X = phi i1 [1], [%X']
1280 // %Y = icmp eq i32 %A, %B
1281 // %Z = xor i1 %X, %Y
1282 // br i1 %Z, ...
1283 //
1284 // Into:
1285 // BB':
1286 // %Y = icmp ne i32 %A, %B
1287 // br i1 %Z, ...
1288
Frits van Bommelea388f22010-12-05 19:06:41 +00001289 PredValueInfoTy XorOpValues;
Chris Lattner2249a0b2010-01-12 02:07:17 +00001290 bool isLHS = true;
Frits van Bommel6033b342010-12-06 23:36:56 +00001291 if (!ComputeValueKnownInPredecessors(BO->getOperand(0), BB, XorOpValues,
1292 WantInteger)) {
Chris Lattner2249a0b2010-01-12 02:07:17 +00001293 assert(XorOpValues.empty());
Frits van Bommel6033b342010-12-06 23:36:56 +00001294 if (!ComputeValueKnownInPredecessors(BO->getOperand(1), BB, XorOpValues,
1295 WantInteger))
Chris Lattner2249a0b2010-01-12 02:07:17 +00001296 return false;
1297 isLHS = false;
1298 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001299
Chris Lattner2249a0b2010-01-12 02:07:17 +00001300 assert(!XorOpValues.empty() &&
1301 "ComputeValueKnownInPredecessors returned true with no values");
1302
1303 // Scan the information to see which is most popular: true or false. The
1304 // predecessors can be of the set true, false, or undef.
1305 unsigned NumTrue = 0, NumFalse = 0;
1306 for (unsigned i = 0, e = XorOpValues.size(); i != e; ++i) {
Frits van Bommelea388f22010-12-05 19:06:41 +00001307 if (isa<UndefValue>(XorOpValues[i].first))
1308 // Ignore undefs for the count.
1309 continue;
1310 if (cast<ConstantInt>(XorOpValues[i].first)->isZero())
Chris Lattner2249a0b2010-01-12 02:07:17 +00001311 ++NumFalse;
1312 else
1313 ++NumTrue;
1314 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001315
Chris Lattner2249a0b2010-01-12 02:07:17 +00001316 // Determine which value to split on, true, false, or undef if neither.
1317 ConstantInt *SplitVal = 0;
1318 if (NumTrue > NumFalse)
1319 SplitVal = ConstantInt::getTrue(BB->getContext());
1320 else if (NumTrue != 0 || NumFalse != 0)
1321 SplitVal = ConstantInt::getFalse(BB->getContext());
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001322
Chris Lattner2249a0b2010-01-12 02:07:17 +00001323 // Collect all of the blocks that this can be folded into so that we can
1324 // factor this once and clone it once.
1325 SmallVector<BasicBlock*, 8> BlocksToFoldInto;
1326 for (unsigned i = 0, e = XorOpValues.size(); i != e; ++i) {
Frits van Bommelea388f22010-12-05 19:06:41 +00001327 if (XorOpValues[i].first != SplitVal &&
1328 !isa<UndefValue>(XorOpValues[i].first))
1329 continue;
Chris Lattner2249a0b2010-01-12 02:07:17 +00001330
1331 BlocksToFoldInto.push_back(XorOpValues[i].second);
1332 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001333
Chris Lattner2dd76572010-01-23 19:16:25 +00001334 // If we inferred a value for all of the predecessors, then duplication won't
1335 // help us. However, we can just replace the LHS or RHS with the constant.
1336 if (BlocksToFoldInto.size() ==
1337 cast<PHINode>(BB->front()).getNumIncomingValues()) {
1338 if (SplitVal == 0) {
1339 // If all preds provide undef, just nuke the xor, because it is undef too.
1340 BO->replaceAllUsesWith(UndefValue::get(BO->getType()));
1341 BO->eraseFromParent();
1342 } else if (SplitVal->isZero()) {
1343 // If all preds provide 0, replace the xor with the other input.
1344 BO->replaceAllUsesWith(BO->getOperand(isLHS));
1345 BO->eraseFromParent();
1346 } else {
1347 // If all preds provide 1, set the computed value to 1.
1348 BO->setOperand(!isLHS, SplitVal);
1349 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001350
Chris Lattner2dd76572010-01-23 19:16:25 +00001351 return true;
1352 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001353
Chris Lattner2249a0b2010-01-12 02:07:17 +00001354 // Try to duplicate BB into PredBB.
Chris Lattner797c4402010-01-12 02:07:50 +00001355 return DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto);
Chris Lattner2249a0b2010-01-12 02:07:17 +00001356}
1357
1358
Chris Lattner78c552e2009-10-11 07:24:57 +00001359/// AddPHINodeEntriesForMappedBlock - We're adding 'NewPred' as a new
1360/// predecessor to the PHIBB block. If it has PHI nodes, add entries for
1361/// NewPred using the entries from OldPred (suitably mapped).
1362static void AddPHINodeEntriesForMappedBlock(BasicBlock *PHIBB,
1363 BasicBlock *OldPred,
1364 BasicBlock *NewPred,
1365 DenseMap<Instruction*, Value*> &ValueMap) {
1366 for (BasicBlock::iterator PNI = PHIBB->begin();
1367 PHINode *PN = dyn_cast<PHINode>(PNI); ++PNI) {
1368 // Ok, we have a PHI node. Figure out what the incoming value was for the
1369 // DestBlock.
1370 Value *IV = PN->getIncomingValueForBlock(OldPred);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001371
Chris Lattner78c552e2009-10-11 07:24:57 +00001372 // Remap the value if necessary.
1373 if (Instruction *Inst = dyn_cast<Instruction>(IV)) {
1374 DenseMap<Instruction*, Value*>::iterator I = ValueMap.find(Inst);
1375 if (I != ValueMap.end())
1376 IV = I->second;
1377 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001378
Chris Lattner78c552e2009-10-11 07:24:57 +00001379 PN->addIncoming(IV, NewPred);
1380 }
1381}
Chris Lattner6bf77502008-04-22 07:05:46 +00001382
Chris Lattner5729d382009-11-07 08:05:03 +00001383/// ThreadEdge - We have decided that it is safe and profitable to factor the
1384/// blocks in PredBBs to one predecessor, then thread an edge from it to SuccBB
1385/// across BB. Transform the IR to reflect this change.
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001386bool JumpThreading::ThreadEdge(BasicBlock *BB,
1387 const SmallVectorImpl<BasicBlock*> &PredBBs,
Chris Lattnerbdbf1a12009-10-11 04:33:43 +00001388 BasicBlock *SuccBB) {
Mike Stumpfe095f32009-05-04 18:40:41 +00001389 // If threading to the same block as we come from, we would infinite loop.
1390 if (SuccBB == BB) {
David Greenefe7fe662010-01-05 01:27:19 +00001391 DEBUG(dbgs() << " Not threading across BB '" << BB->getName()
Daniel Dunbar93b67e42009-07-26 07:49:05 +00001392 << "' - would thread to self!\n");
Mike Stumpfe095f32009-05-04 18:40:41 +00001393 return false;
1394 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001395
Mike Stumpfe095f32009-05-04 18:40:41 +00001396 // If threading this would thread across a loop header, don't thread the edge.
1397 // See the comments above FindLoopHeaders for justifications and caveats.
1398 if (LoopHeaders.count(BB)) {
David Greenefe7fe662010-01-05 01:27:19 +00001399 DEBUG(dbgs() << " Not threading across loop header BB '" << BB->getName()
Daniel Dunbar93b67e42009-07-26 07:49:05 +00001400 << "' to dest BB '" << SuccBB->getName()
1401 << "' - it might create an irreducible loop!\n");
Mike Stumpfe095f32009-05-04 18:40:41 +00001402 return false;
1403 }
1404
Chris Lattner78c552e2009-10-11 07:24:57 +00001405 unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
1406 if (JumpThreadCost > Threshold) {
David Greenefe7fe662010-01-05 01:27:19 +00001407 DEBUG(dbgs() << " Not threading BB '" << BB->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +00001408 << "' - Cost is too high: " << JumpThreadCost << "\n");
1409 return false;
1410 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001411
Chris Lattner5729d382009-11-07 08:05:03 +00001412 // And finally, do it! Start by factoring the predecessors is needed.
1413 BasicBlock *PredBB;
1414 if (PredBBs.size() == 1)
1415 PredBB = PredBBs[0];
1416 else {
David Greenefe7fe662010-01-05 01:27:19 +00001417 DEBUG(dbgs() << " Factoring out " << PredBBs.size()
Chris Lattner5729d382009-11-07 08:05:03 +00001418 << " common predecessors.\n");
1419 PredBB = SplitBlockPredecessors(BB, &PredBBs[0], PredBBs.size(),
1420 ".thr_comm", this);
1421 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001422
Mike Stumpfe095f32009-05-04 18:40:41 +00001423 // And finally, do it!
David Greenefe7fe662010-01-05 01:27:19 +00001424 DEBUG(dbgs() << " Threading edge from '" << PredBB->getName() << "' to '"
Daniel Dunbar460f6562009-07-26 09:48:23 +00001425 << SuccBB->getName() << "' with cost: " << JumpThreadCost
Daniel Dunbar93b67e42009-07-26 07:49:05 +00001426 << ", across block:\n "
1427 << *BB << "\n");
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001428
Owen Andersonc809d902010-09-14 20:57:41 +00001429 LVI->threadEdge(PredBB, BB, SuccBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001430
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001431 // We are going to have to map operands from the original BB block to the new
1432 // copy of the block 'NewBB'. If there are PHI nodes in BB, evaluate them to
1433 // account for entry from PredBB.
1434 DenseMap<Instruction*, Value*> ValueMapping;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001435
1436 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(),
1437 BB->getName()+".thread",
Owen Anderson1d0be152009-08-13 21:58:54 +00001438 BB->getParent(), BB);
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001439 NewBB->moveAfter(PredBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001440
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001441 BasicBlock::iterator BI = BB->begin();
1442 for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
1443 ValueMapping[PN] = PN->getIncomingValueForBlock(PredBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001444
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001445 // Clone the non-phi instructions of BB into NewBB, keeping track of the
1446 // mapping and using it to remap operands in the cloned instructions.
1447 for (; !isa<TerminatorInst>(BI); ++BI) {
Nick Lewycky67760642009-09-27 07:38:41 +00001448 Instruction *New = BI->clone();
Daniel Dunbar460f6562009-07-26 09:48:23 +00001449 New->setName(BI->getName());
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001450 NewBB->getInstList().push_back(New);
1451 ValueMapping[BI] = New;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001452
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001453 // Remap operands to patch up intra-block references.
1454 for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
Dan Gohmanf530c922009-07-02 00:17:47 +00001455 if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
1456 DenseMap<Instruction*, Value*>::iterator I = ValueMapping.find(Inst);
1457 if (I != ValueMapping.end())
1458 New->setOperand(i, I->second);
1459 }
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001460 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001461
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001462 // We didn't copy the terminator from BB over to NewBB, because there is now
1463 // an unconditional jump to SuccBB. Insert the unconditional jump.
1464 BranchInst::Create(SuccBB, NewBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001465
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001466 // Check to see if SuccBB has PHI nodes. If so, we need to add entries to the
1467 // PHI nodes for NewBB now.
Chris Lattner78c552e2009-10-11 07:24:57 +00001468 AddPHINodeEntriesForMappedBlock(SuccBB, BB, NewBB, ValueMapping);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001469
Chris Lattner433a0db2009-10-10 09:05:58 +00001470 // If there were values defined in BB that are used outside the block, then we
1471 // now have to update all uses of the value to use either the original value,
1472 // the cloned value, or some PHI derived value. This can require arbitrary
1473 // PHI insertion, of which we are prepared to do, clean these up now.
1474 SSAUpdater SSAUpdate;
1475 SmallVector<Use*, 16> UsesToRename;
1476 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
1477 // Scan all uses of this instruction to see if it is used outside of its
1478 // block, and if so, record them in UsesToRename.
1479 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
1480 ++UI) {
1481 Instruction *User = cast<Instruction>(*UI);
1482 if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
1483 if (UserPN->getIncomingBlock(UI) == BB)
1484 continue;
1485 } else if (User->getParent() == BB)
1486 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001487
Chris Lattner433a0db2009-10-10 09:05:58 +00001488 UsesToRename.push_back(&UI.getUse());
1489 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001490
Chris Lattner433a0db2009-10-10 09:05:58 +00001491 // If there are no uses outside the block, we're done with this instruction.
1492 if (UsesToRename.empty())
1493 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001494
David Greenefe7fe662010-01-05 01:27:19 +00001495 DEBUG(dbgs() << "JT: Renaming non-local uses of: " << *I << "\n");
Chris Lattner433a0db2009-10-10 09:05:58 +00001496
1497 // We found a use of I outside of BB. Rename all uses of I that are outside
1498 // its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
1499 // with the two values we know.
Duncan Sandsfc6e29d2010-09-02 08:14:03 +00001500 SSAUpdate.Initialize(I->getType(), I->getName());
Chris Lattner433a0db2009-10-10 09:05:58 +00001501 SSAUpdate.AddAvailableValue(BB, I);
1502 SSAUpdate.AddAvailableValue(NewBB, ValueMapping[I]);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001503
Chris Lattner433a0db2009-10-10 09:05:58 +00001504 while (!UsesToRename.empty())
1505 SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
David Greenefe7fe662010-01-05 01:27:19 +00001506 DEBUG(dbgs() << "\n");
Chris Lattner433a0db2009-10-10 09:05:58 +00001507 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001508
1509
Chris Lattneref0c6742008-12-01 04:48:07 +00001510 // Ok, NewBB is good to go. Update the terminator of PredBB to jump to
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001511 // NewBB instead of BB. This eliminates predecessors from BB, which requires
1512 // us to simplify any PHI nodes in BB.
1513 TerminatorInst *PredTerm = PredBB->getTerminator();
1514 for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
1515 if (PredTerm->getSuccessor(i) == BB) {
Owen Anderson36c4deb2010-09-29 20:34:41 +00001516 BB->removePredecessor(PredBB, true);
Chris Lattnerbd3401f2008-04-20 22:39:42 +00001517 PredTerm->setSuccessor(i, NewBB);
1518 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001519
Chris Lattneref0c6742008-12-01 04:48:07 +00001520 // At this point, the IR is fully up to date and consistent. Do a quick scan
1521 // over the new instructions and zap any that are constants or dead. This
1522 // frequently happens because of phi translation.
Chris Lattner972a46c2010-01-12 20:41:47 +00001523 SimplifyInstructionsInBlock(NewBB, TD);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001524
Mike Stumpfe095f32009-05-04 18:40:41 +00001525 // Threaded an edge!
1526 ++NumThreads;
1527 return true;
Chris Lattner177480b2008-04-20 21:13:06 +00001528}
Chris Lattner78c552e2009-10-11 07:24:57 +00001529
1530/// DuplicateCondBranchOnPHIIntoPred - PredBB contains an unconditional branch
1531/// to BB which contains an i1 PHI node and a conditional branch on that PHI.
1532/// If we can duplicate the contents of BB up into PredBB do so now, this
1533/// improves the odds that the branch will be on an analyzable instruction like
1534/// a compare.
1535bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
Chris Lattner2249a0b2010-01-12 02:07:17 +00001536 const SmallVectorImpl<BasicBlock *> &PredBBs) {
1537 assert(!PredBBs.empty() && "Can't handle an empty set");
1538
Chris Lattner78c552e2009-10-11 07:24:57 +00001539 // If BB is a loop header, then duplicating this block outside the loop would
1540 // cause us to transform this into an irreducible loop, don't do this.
1541 // See the comments above FindLoopHeaders for justifications and caveats.
1542 if (LoopHeaders.count(BB)) {
David Greenefe7fe662010-01-05 01:27:19 +00001543 DEBUG(dbgs() << " Not duplicating loop header '" << BB->getName()
Chris Lattner2249a0b2010-01-12 02:07:17 +00001544 << "' into predecessor block '" << PredBBs[0]->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +00001545 << "' - it might create an irreducible loop!\n");
1546 return false;
1547 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001548
Chris Lattner78c552e2009-10-11 07:24:57 +00001549 unsigned DuplicationCost = getJumpThreadDuplicationCost(BB);
1550 if (DuplicationCost > Threshold) {
David Greenefe7fe662010-01-05 01:27:19 +00001551 DEBUG(dbgs() << " Not duplicating BB '" << BB->getName()
Chris Lattner78c552e2009-10-11 07:24:57 +00001552 << "' - Cost is too high: " << DuplicationCost << "\n");
1553 return false;
1554 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001555
Chris Lattner2249a0b2010-01-12 02:07:17 +00001556 // And finally, do it! Start by factoring the predecessors is needed.
1557 BasicBlock *PredBB;
1558 if (PredBBs.size() == 1)
1559 PredBB = PredBBs[0];
1560 else {
1561 DEBUG(dbgs() << " Factoring out " << PredBBs.size()
1562 << " common predecessors.\n");
1563 PredBB = SplitBlockPredecessors(BB, &PredBBs[0], PredBBs.size(),
1564 ".thr_comm", this);
1565 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001566
Chris Lattner78c552e2009-10-11 07:24:57 +00001567 // Okay, we decided to do this! Clone all the instructions in BB onto the end
1568 // of PredBB.
David Greenefe7fe662010-01-05 01:27:19 +00001569 DEBUG(dbgs() << " Duplicating block '" << BB->getName() << "' into end of '"
Chris Lattner78c552e2009-10-11 07:24:57 +00001570 << PredBB->getName() << "' to eliminate branch on phi. Cost: "
1571 << DuplicationCost << " block is:" << *BB << "\n");
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001572
Chris Lattner2249a0b2010-01-12 02:07:17 +00001573 // Unless PredBB ends with an unconditional branch, split the edge so that we
1574 // can just clone the bits from BB into the end of the new PredBB.
Chris Lattnerd6688392010-01-23 19:21:31 +00001575 BranchInst *OldPredBranch = dyn_cast<BranchInst>(PredBB->getTerminator());
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001576
Chris Lattnerd6688392010-01-23 19:21:31 +00001577 if (OldPredBranch == 0 || !OldPredBranch->isUnconditional()) {
Chris Lattner2249a0b2010-01-12 02:07:17 +00001578 PredBB = SplitEdge(PredBB, BB, this);
1579 OldPredBranch = cast<BranchInst>(PredBB->getTerminator());
1580 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001581
Chris Lattner78c552e2009-10-11 07:24:57 +00001582 // We are going to have to map operands from the original BB block into the
1583 // PredBB block. Evaluate PHI nodes in BB.
1584 DenseMap<Instruction*, Value*> ValueMapping;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001585
Chris Lattner78c552e2009-10-11 07:24:57 +00001586 BasicBlock::iterator BI = BB->begin();
1587 for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
1588 ValueMapping[PN] = PN->getIncomingValueForBlock(PredBB);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001589
Chris Lattner78c552e2009-10-11 07:24:57 +00001590 // Clone the non-phi instructions of BB into PredBB, keeping track of the
1591 // mapping and using it to remap operands in the cloned instructions.
1592 for (; BI != BB->end(); ++BI) {
1593 Instruction *New = BI->clone();
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001594
Chris Lattner78c552e2009-10-11 07:24:57 +00001595 // Remap operands to patch up intra-block references.
1596 for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
1597 if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
1598 DenseMap<Instruction*, Value*>::iterator I = ValueMapping.find(Inst);
1599 if (I != ValueMapping.end())
1600 New->setOperand(i, I->second);
1601 }
Chris Lattner972a46c2010-01-12 20:41:47 +00001602
1603 // If this instruction can be simplified after the operands are updated,
1604 // just use the simplified value instead. This frequently happens due to
1605 // phi translation.
1606 if (Value *IV = SimplifyInstruction(New, TD)) {
1607 delete New;
1608 ValueMapping[BI] = IV;
1609 } else {
1610 // Otherwise, insert the new instruction into the block.
1611 New->setName(BI->getName());
1612 PredBB->getInstList().insert(OldPredBranch, New);
1613 ValueMapping[BI] = New;
1614 }
Chris Lattner78c552e2009-10-11 07:24:57 +00001615 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001616
Chris Lattner78c552e2009-10-11 07:24:57 +00001617 // Check to see if the targets of the branch had PHI nodes. If so, we need to
1618 // add entries to the PHI nodes for branch from PredBB now.
1619 BranchInst *BBBranch = cast<BranchInst>(BB->getTerminator());
1620 AddPHINodeEntriesForMappedBlock(BBBranch->getSuccessor(0), BB, PredBB,
1621 ValueMapping);
1622 AddPHINodeEntriesForMappedBlock(BBBranch->getSuccessor(1), BB, PredBB,
1623 ValueMapping);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001624
Chris Lattner78c552e2009-10-11 07:24:57 +00001625 // If there were values defined in BB that are used outside the block, then we
1626 // now have to update all uses of the value to use either the original value,
1627 // the cloned value, or some PHI derived value. This can require arbitrary
1628 // PHI insertion, of which we are prepared to do, clean these up now.
1629 SSAUpdater SSAUpdate;
1630 SmallVector<Use*, 16> UsesToRename;
1631 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
1632 // Scan all uses of this instruction to see if it is used outside of its
1633 // block, and if so, record them in UsesToRename.
1634 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
1635 ++UI) {
1636 Instruction *User = cast<Instruction>(*UI);
1637 if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
1638 if (UserPN->getIncomingBlock(UI) == BB)
1639 continue;
1640 } else if (User->getParent() == BB)
1641 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001642
Chris Lattner78c552e2009-10-11 07:24:57 +00001643 UsesToRename.push_back(&UI.getUse());
1644 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001645
Chris Lattner78c552e2009-10-11 07:24:57 +00001646 // If there are no uses outside the block, we're done with this instruction.
1647 if (UsesToRename.empty())
1648 continue;
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001649
David Greenefe7fe662010-01-05 01:27:19 +00001650 DEBUG(dbgs() << "JT: Renaming non-local uses of: " << *I << "\n");
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001651
Chris Lattner78c552e2009-10-11 07:24:57 +00001652 // We found a use of I outside of BB. Rename all uses of I that are outside
1653 // its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
1654 // with the two values we know.
Duncan Sandsfc6e29d2010-09-02 08:14:03 +00001655 SSAUpdate.Initialize(I->getType(), I->getName());
Chris Lattner78c552e2009-10-11 07:24:57 +00001656 SSAUpdate.AddAvailableValue(BB, I);
1657 SSAUpdate.AddAvailableValue(PredBB, ValueMapping[I]);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001658
Chris Lattner78c552e2009-10-11 07:24:57 +00001659 while (!UsesToRename.empty())
1660 SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
David Greenefe7fe662010-01-05 01:27:19 +00001661 DEBUG(dbgs() << "\n");
Chris Lattner78c552e2009-10-11 07:24:57 +00001662 }
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001663
Chris Lattner78c552e2009-10-11 07:24:57 +00001664 // PredBB no longer jumps to BB, remove entries in the PHI node for the edge
1665 // that we nuked.
Owen Anderson36c4deb2010-09-29 20:34:41 +00001666 BB->removePredecessor(PredBB, true);
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001667
Chris Lattner78c552e2009-10-11 07:24:57 +00001668 // Remove the unconditional branch at the end of the PredBB block.
1669 OldPredBranch->eraseFromParent();
Frits van Bommel6f9a8302010-12-05 19:02:47 +00001670
Chris Lattner78c552e2009-10-11 07:24:57 +00001671 ++NumDupes;
1672 return true;
1673}
1674
1675