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Fix PR1015 and Transforms/IndVarsSimplify/2007-01-06-TripCount.ll, a

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miscompilation of Qt.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32974 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-01-07 02:24:26 +00:00
parent b4b512bc6e
commit 8b0e3602e2
1 changed files with 15 additions and 1 deletions
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16
lib/Analysis/ScalarEvolution.cpp
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@ -1498,12 +1498,26 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
BranchInst *ExitBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
if (ExitBr == 0) return UnknownValue;
assert(ExitBr->isConditional() && "If unconditional, it can't be in loop!");
// At this point, we know we have a conditional branch that determines whether
// the loop is exited. However, we don't know if the branch is executed each
// time through the loop. If not, then the execution count of the branch will
// not be equal to the trip count of the loop.
//
// Currently we check for this by checking to see if the Exit branch goes to
// the loop header. If so, we know it will always execute the same number of
// times as the loop. More extensive analysis could be done to handle more
// cases here.
if (ExitBr->getSuccessor(0) != L->getHeader() &&
ExitBr->getSuccessor(1) != L->getHeader())
return UnknownValue;
ICmpInst *ExitCond = dyn_cast<ICmpInst>(ExitBr->getCondition());
// If its not an integer comparison then compute it the hard way.
// Note that ICmpInst deals with pointer comparisons too so we must check
// the type of the operand.
if (ExitCond == 0 || !ExitCond->getOperand(0)->getType()->isIntegral())
if (ExitCond == 0 || isa<PointerType>(ExitCond->getOperand(0)->getType()))
return ComputeIterationCountExhaustively(L, ExitBr->getCondition(),
ExitBr->getSuccessor(0) == ExitBlock);