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

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 453194664d
commit de7f699754
1 changed files with 15 additions and 13 deletions
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28
llvm/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 =