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LoopIdiom: Fix a serious missed optimization: we only turned top-level loops into memmove.

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Thanks to Preston Briggs for catching this!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167045 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-10-30 19:49:39 +00:00
parent 8a69a95f91
commit 415f869cf3
2 changed files with 47 additions and 4 deletions
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9
lib/Transforms/Scalar/LoopIdiomRecognize.cpp
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@@ -555,10 +555,11 @@ processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
// can safely emit a memcpy.
OwningPtr<Dependence> Dep(DA.depends(SI, LI, true));
if (Dep) {
// If there is a dependence but the direction is positive we can still
// safely turn this into memmove.
if (Dep->getLevels() != 1 ||
Dep->getDirection(1) != Dependence::DVEntry::GT)
// If there is a dependence but the direction is positive (or none) we can
// still safely turn this into memmove.
unsigned Direction = Dep->getDirection(Dep->getLevels());
if (Direction != Dependence::DVEntry::NONE &&
Direction != Dependence::DVEntry::GT)
return false;
isMemcpySafe = false;
}