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enhance jump threading to preserve TBAA information when PRE'ing loads,

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fixing rdar://11039258, an issue that came up when inspecting clang's 
bootstrapped codegen.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152635 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2012-03-13 18:07:41 +00:00
parent f1ce79f3c3
commit 5161de6ebb
4 changed files with 76 additions and 9 deletions
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13
lib/Transforms/Scalar/JumpThreading.cpp
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@ -857,6 +857,9 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
if (BBIt != LoadBB->begin())
return false;
// If all of the loads and stores that feed the value have the same TBAA tag,
// then we can propagate it onto any newly inserted loads.
MDNode *TBAATag = LI->getMetadata(LLVMContext::MD_tbaa);
SmallPtrSet<BasicBlock*, 8> PredsScanned;
typedef SmallVector<std::pair<BasicBlock*, Value*>, 8> AvailablePredsTy;
@ -875,11 +878,16 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// Scan the predecessor to see if the value is available in the pred.
BBIt = PredBB->end();
Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6);
MDNode *ThisTBAATag = 0;
Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6,
0, &ThisTBAATag);
if (!PredAvailable) {
OneUnavailablePred = PredBB;
continue;
}
// If tbaa tags disagree or are not present, forget about them.
if (TBAATag != ThisTBAATag) TBAATag = 0;
// If so, this load is partially redundant. Remember this info so that we
// can create a PHI node.
@ -939,6 +947,9 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
LI->getAlignment(),
UnavailablePred->getTerminator());
NewVal->setDebugLoc(LI->getDebugLoc());
if (TBAATag)
NewVal->setMetadata(LLVMContext::MD_tbaa, TBAATag);
AvailablePreds.push_back(std::make_pair(UnavailablePred, NewVal));
}