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Don't split any loop backedges, including backedges of loops other than

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the active loop. This is generally desirable, and it avoids trouble
in situations such as the testcase in PR9123, though the failure
mode depends on use-list order, so it is infeasible to test.

llvm-svn: 125065
This commit is contained in:
Dan Gohman 2011-02-08 00:55:13 +00:00
parent a5e0ea6e4e
commit ae7dba9ba8
1 changed files with 15 additions and 13 deletions
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28
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -3544,21 +3544,23 @@ void LSRInstance::RewriteForPHI(PHINode *PN,
// is the canonical backedge for this loop, which complicates post-inc
// users.
if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
!isa<IndirectBrInst>(BB->getTerminator()) &&
(PN->getParent() != L->getHeader() || !L->contains(BB))) {
// Split the critical edge.
BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
!isa<IndirectBrInst>(BB->getTerminator())) {
Loop *PNLoop = LI.getLoopFor(PN->getParent());
if (!PNLoop || PN->getParent() != PNLoop->getHeader()) {
// Split the critical edge.
BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
// If PN is outside of the loop and BB is in the loop, we want to
// move the block to be immediately before the PHI block, not
// immediately after BB.
if (L->contains(BB) && !L->contains(PN))
NewBB->moveBefore(PN->getParent());
// If PN is outside of the loop and BB is in the loop, we want to
// move the block to be immediately before the PHI block, not
// immediately after BB.
if (L->contains(BB) && !L->contains(PN))
NewBB->moveBefore(PN->getParent());
// Splitting the edge can reduce the number of PHI entries we have.
e = PN->getNumIncomingValues();
BB = NewBB;
i = PN->getBasicBlockIndex(BB);
// Splitting the edge can reduce the number of PHI entries we have.
e = PN->getNumIncomingValues();
BB = NewBB;
i = PN->getBasicBlockIndex(BB);
}
}
std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =