From 027bc80928e00f143db3de878b4cf828f305a92a Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Sat, 22 Nov 2014 04:52:38 +0000 Subject: InstCombine: Preserve nsw for (mul %V, -1) -> (sub 0, %V) llvm-svn: 222604 --- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 8c48dce81de..c96c2d62255 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -136,8 +136,13 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { if (Value *V = SimplifyUsingDistributiveLaws(I)) return ReplaceInstUsesWith(I, V); - if (match(Op1, m_AllOnes())) // X * -1 == 0 - X - return BinaryOperator::CreateNeg(Op0, I.getName()); + // X * -1 == 0 - X + if (match(Op1, m_AllOnes())) { + BinaryOperator *BO = BinaryOperator::CreateNeg(Op0, I.getName()); + if (I.hasNoSignedWrap()) + BO->setHasNoSignedWrap(); + return BO; + } // Also allow combining multiply instructions on vectors. { -- cgit v1.2.3