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Fix a regression from last night, which caused this pass to create invalid

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code for IV uses outside of loops that are not dominated by the latch block.
We should only convert these uses to use the post-inc value if they ARE
dominated by the latch block.

Also use a new LoopInfo method to simplify some code.

This fixes Transforms/LoopStrengthReduce/2005-09-12-UsesOutOutsideOfLoop.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23318 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-09-12 17:11:27 +00:00
parent e4b56572f9
commit 12b50410cd
1 changed files with 6 additions and 8 deletions
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14
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -353,7 +353,11 @@ bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
// Okay, we found a user that we cannot reduce. Analyze the instruction
// and decide what to do with it. If we are a use inside of the loop, use
// the value before incrementation, otherwise use it after incrementation.
if (L->contains(User->getParent())) {
if (L->contains(User->getParent()) ||
// Alternatively, if we are a use outside of the loop, but is not
// dominated by the latch block, we have to use the preincremented
// value.
!DS->dominates(L->getLoopLatch(), User->getParent())) {
IVUsesByStride[Stride].addUser(Start, User, I);
} else {
// The value used will be incremented by the stride more than we are
@ -784,13 +788,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
Instruction *PreInsertPt = Preheader->getTerminator();
Instruction *PhiInsertBefore = L->getHeader()->begin();
assert(isa<PHINode>(PhiInsertBefore) &&
"How could this loop have IV's without any phis?");
PHINode *SomeLoopPHI = cast<PHINode>(PhiInsertBefore);
assert(SomeLoopPHI->getNumIncomingValues() == 2 &&
"This loop isn't canonicalized right");
BasicBlock *LatchBlock =
SomeLoopPHI->getIncomingBlock(SomeLoopPHI->getIncomingBlock(0) == Preheader);
BasicBlock *LatchBlock = L->getLoopLatch();
// Create a new Phi for this base, and stick it in the loop header.
const Type *ReplacedTy = CommonExprs->getType();