From 2d1e0899e96ff3912bc6ee5ea85814700532cbd2 Mon Sep 17 00:00:00 2001 From: Simon Pilgrim Date: Fri, 30 Aug 2019 17:58:55 +0000 Subject: [TargetLowering] SimplifyDemandedBits ADD/SUB/MUL - correctly inherit SDNodeFlags from the original node. Just disable NSW/NUW flags. This matches what we're already doing for the other situations for these nodes, it was just missed for the demanded constant case. Noticed by inspection - confirmed in offline discussion with @spatel. I've checked we have test coverage in the x86 extract-bits.ll and extract-lowbits.ll tests llvm-svn: 370497 --- llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'llvm/lib/CodeGen') diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp index 79caf880219..35ca9fa4f2f 100644 --- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -1953,10 +1953,8 @@ bool TargetLowering::SimplifyDemandedBits( if (C && !C->isAllOnesValue() && !C->isOne() && (C->getAPIntValue() | HighMask).isAllOnesValue()) { SDValue Neg1 = TLO.DAG.getAllOnesConstant(dl, VT); - // We can't guarantee that the new math op doesn't wrap, so explicitly - // clear those flags to prevent folding with a potential existing node - // that has those flags set. - SDNodeFlags Flags; + // Disable the nsw and nuw flags. We can no longer guarantee that we + // won't wrap after simplification. Flags.setNoSignedWrap(false); Flags.setNoUnsignedWrap(false); SDValue NewOp = TLO.DAG.getNode(Op.getOpcode(), dl, VT, Op0, Neg1, Flags); -- cgit v1.2.3