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Address review comments.

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- Reword comments.
- Allow undefined behavior interfering with undefined behavior.
- Add address space checks.

llvm-svn: 138619
This commit is contained in:
Benjamin Kramer 2011-08-26 02:25:55 +00:00
parent dc1c57af91
commit 0e1a09f38c
1 changed files with 8 additions and 9 deletions
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17
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2729,7 +2729,7 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
if (!C)
return false;
if (!I->hasOneUse()) // FIXME: There is no reason to limit this to one use.
if (!I->hasOneUse()) // Only look at single-use instructions, for compile time
return false;
if (C->isNullValue()) {
@ -2738,8 +2738,7 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
// Now make sure that there are no instructions in between that can alter
// control flow (eg. calls)
for (BasicBlock::iterator i = ++BasicBlock::iterator(I); &*i != Use; ++i)
if (i == I->getParent()->end() ||
!i->isSafeToSpeculativelyExecute())
if (i == I->getParent()->end() || i->mayHaveSideEffects())
return false;
// Look through GEPs. A load from a GEP derived from NULL is still undefined
@ -2751,13 +2750,13 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
if (BitCastInst *BC = dyn_cast<BitCastInst>(Use))
return passingValueIsAlwaysUndefined(V, BC);
// load from null is undefined
if (isa<LoadInst>(Use))
return true;
// Load from null is undefined.
if (LoadInst *LI = dyn_cast<LoadInst>(Use))
return LI->getPointerAddressSpace() == 0;
// store to null is undef
if (isa<StoreInst>(Use) && Use->getOperand(1) == I)
return true;
// Store to null is undefined.
if (StoreInst *SI = dyn_cast<StoreInst>(Use))
return SI->getPointerAddressSpace() == 0 && SI->getPointerOperand() == I;
}
return false;
}