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Fix a bug in the previous checkin: if the exit block is not the same as

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the back-edge block, we must check the preincremented value.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12968 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-04-15 20:26:22 +00:00
parent b75a316758
commit d244057a48
1 changed files with 22 additions and 6 deletions
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22
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -209,13 +209,29 @@ void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()))
InstructionsToDelete.insert(Cond);
// If the exiting block is not the same as the backedge block, we must compare
// against the preincremented value, otherwise we prefer to compare against
// the post-incremented value.
BasicBlock *Header = L->getHeader();
pred_iterator HPI = pred_begin(Header);
assert(HPI != pred_end(Header) && "Loop with zero preds???");
if (!L->contains(*HPI)) ++HPI;
assert(HPI != pred_end(Header) && L->contains(*HPI) &&
"No backedge in loop?");
SCEVHandle TripCount = IterationCount;
Value *IndVar;
if (*HPI == ExitingBlock) {
// The IterationCount expression contains the number of times that the
// backedge actually branches to the loop header. This is one less than the
// number of times the loop executes, so add one to it.
Constant *OneC = ConstantInt::get(IterationCount->getType(), 1);
SCEVHandle TripCount=SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC));
Value *IndVar = L->getCanonicalInductionVariableIncrement();
TripCount = SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC));
IndVar = L->getCanonicalInductionVariableIncrement();
} else {
// We have to use the preincremented value...
IndVar = L->getCanonicalInductionVariable();
}
// Expand the code for the iteration count into the preheader of the loop.
BasicBlock *Preheader = L->getLoopPreheader();