From a58fb48a5596d7cc6decebbbb845f3a47e5649b5 Mon Sep 17 00:00:00 2001 From: Nick Lewycky Date: Mon, 24 Oct 2011 21:02:38 +0000 Subject: Now that we look at all the header PHIs, we need to consider all the header PHIs when deciding that the loop has stopped evolving. Fixes miscompile in the gcc torture testsuite! llvm-svn: 142843 --- llvm/lib/Analysis/ScalarEvolution.cpp | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) (limited to 'llvm/lib/Analysis/ScalarEvolution.cpp') diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 1ab6a406fce..f65cf343355 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -4844,12 +4844,12 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN, // EvaluateExpression adds non-phi values to the CurrentIterVals map. DenseMap NextIterVals; Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD); - if (NextPHI == CurrentIterVals[PN]) - return RetVal = NextPHI; // Stopped evolving! if (NextPHI == 0) return 0; // Couldn't evaluate! NextIterVals[PN] = NextPHI; + bool StoppedEvolving = NextPHI == CurrentIterVals[PN]; + // Also evaluate the other PHI nodes. However, we don't get to stop if we // cease to be able to evaluate one of them or if they stop evolving, // because that doesn't necessarily prevent us from computing PN. @@ -4858,11 +4858,19 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN, PHINode *PHI = dyn_cast(I->first); if (!PHI || PHI == PN || PHI->getParent() != Header) continue; Constant *&NextPHI = NextIterVals[PHI]; - if (NextPHI) continue; // Already computed! - - Value *BEValue = PHI->getIncomingValue(SecondIsBackedge); - NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD); + if (!NextPHI) { // Not already computed. + Value *BEValue = PHI->getIncomingValue(SecondIsBackedge); + NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD); + } + if (NextPHI != I->second) + StoppedEvolving = false; } + + // If all entries in CurrentIterVals == NextIterVals then we can stop + // iterating, the loop can't continue to change. + if (StoppedEvolving) + return RetVal = CurrentIterVals[PN]; + CurrentIterVals.swap(NextIterVals); } } -- cgit v1.2.3