From f23bbbae4ab2e03d6663013671fe99b094fa6529 Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Thu, 4 Sep 2014 00:23:13 +0000 Subject: [PATCH] IndVarSimplify: Address review comments for r217102 No functional change intended, just some cleanups and comments added. llvm-svn: 217115 --- lib/Transforms/Scalar/IndVarSimplify.cpp | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index a5f0dae87ea..27e5ec8cf40 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -1644,16 +1644,19 @@ LinearFunctionTestReplace(Loop *L, // The BackedgeTaken expression contains the number of times that the // backedge branches to the loop header. This is one less than the // number of times the loop executes, so use the incremented indvar. - llvm::Value *IncrementedIndvar = IndVar->getIncomingValueForBlock(L->getExitingBlock()); + llvm::Value *IncrementedIndvar = + IndVar->getIncomingValueForBlock(L->getExitingBlock()); const auto *IncrementedIndvarSCEV = cast(SE->getSCEV(IncrementedIndvar)); // It is unsafe to use the incremented indvar if it has a wrapping flag, we // don't want to compare against a poison value. Check the SCEV that // corresponds to the incremented indvar, the SCEVExpander will only insert // flags in the IR if the SCEV originally had wrapping flags. - if (ScalarEvolution::maskFlags(IncrementedIndvarSCEV->getNoWrapFlags(), - SCEV::FlagNUW | SCEV::FlagNSW) == - SCEV::FlagAnyWrap) { + // FIXME: In theory, SCEV could drop flags even though they exist in IR. + // A more robust solution would involve getting a new expression for + // CmpIndVar by applying non-NSW/NUW AddExprs. + if (!ScalarEvolution::maskFlags(IncrementedIndvarSCEV->getNoWrapFlags(), + SCEV::FlagNUW | SCEV::FlagNSW)) { // Add one to the "backedge-taken" count to get the trip count. // This addition may overflow, which is valid as long as the comparison is // truncated to BackedgeTakenCount->getType().