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Teach SplitCriticalEdge to update LoopInfo if it is alive. This fixes

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a problem in LoopStrengthReduction, where it would split critical edges
then confused itself with outdated loop information.

llvm-svn: 22776
This commit is contained in:
Chris Lattner 2005-08-13 01:38:43 +00:00
parent 87bcd2794b
commit 2681a83c43
1 changed files with 31 additions and 0 deletions
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31
lib/Transforms/Utils/BreakCriticalEdges.cpp
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@ -19,6 +19,7 @@
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
@ -37,6 +38,7 @@ namespace {
AU.addPreserved<ImmediateDominators>();
AU.addPreserved<DominatorTree>();
AU.addPreserved<DominanceFrontier>();
AU.addPreserved<LoopInfo>();
// No loop canonicalization guarantees are broken by this pass.
AU.addPreservedID(LoopSimplifyID);
@ -171,5 +173,34 @@ bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
NewDFSet.insert(DestBB);
DF->addBasicBlock(NewBB, NewDFSet);
}
// Update LoopInfo if it is around.
if (LoopInfo *LI = P->getAnalysisToUpdate<LoopInfo>()) {
// If one or the other blocks were not in a loop, the new block is not
// either, and thus LI doesn't need to be updated.
if (Loop *TIL = LI->getLoopFor(TIBB))
if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
if (TIL == DestLoop) {
// Both in the same loop, the NewBB joins loop.
DestLoop->addBasicBlockToLoop(NewBB, *LI);
} else if (TIL->contains(DestLoop->getHeader())) {
// Edge from an outer loop to an inner loop. Add to the outer lopo.
TIL->addBasicBlockToLoop(NewBB, *LI);
} else if (DestLoop->contains(TIL->getHeader())) {
// Edge from an inner loop to an outer loop. Add to the outer lopo.
DestLoop->addBasicBlockToLoop(NewBB, *LI);
} else {
// Edge from two loops with no containment relation. Because these
// are natural loops, we know that the destination block must be the
// header of its loop (adding a branch into a loop elsewhere would
// create an irreducible loop).
assert(DestLoop->getHeader() == DestBB &&
"Should not create irreducible loops!");
if (Loop *P = DestLoop->getParentLoop())
P->addBasicBlockToLoop(NewBB, *LI);
}
}
}
return true;
}