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Fix potential miscompilations: InstCombine/2004-09-20-BadLoadCombine*.llx

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16447 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-09-20 10:15:10 +00:00
parent c804d530c5
commit 79f0c8e4ee
1 changed files with 19 additions and 7 deletions
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26
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3064,21 +3064,33 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
Value *V1 = InsertNewInstBefore(new LoadInst(SI->getOperand(1),
SI->getOperand(1)->getName()+".val"), *SI);
SI->getOperand(1)->getName()+".val"), LI);
Value *V2 = InsertNewInstBefore(new LoadInst(SI->getOperand(2),
SI->getOperand(2)->getName()+".val"), *SI);
SI->getOperand(2)->getName()+".val"), LI);
return new SelectInst(SI->getCondition(), V1, V2);
}
} else if (PHINode *PN = dyn_cast<PHINode>(Op)) {
// load (phi (&V1, &V2, &V3)) --> phi(load &V1, load &V2, load &V3)
bool Safe = true;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
bool Safe = PN->getParent() == LI.getParent();
// Scan all of the instructions between the PHI and the load to make
// sure there are no instructions that might possibly alter the value
// loaded from the PHI.
if (Safe) {
BasicBlock::iterator I = &LI;
for (--I; !isa<PHINode>(I); --I)
if (isa<StoreInst>(I) || isa<CallInst>(I)) {
Safe = false;
break;
}
}
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e && Safe; ++i)
if (!isSafeToLoadUnconditionally(PN->getIncomingValue(i),
PN->getIncomingBlock(i)->getTerminator())) {
PN->getIncomingBlock(i)->getTerminator()))
Safe = false;
break;
}
if (Safe) {
// Create the PHI.
PHINode *NewPN = new PHINode(LI.getType(), PN->getName());