From 93c91e39b29142dec1d03a30df9f6e757f56c193 Mon Sep 17 00:00:00 2001 From: Dimitry Andric Date: Wed, 19 Jul 2017 07:02:10 +0000 Subject: Vendor import of llvm trunk r308421: https://llvm.org/svn/llvm-project/llvm/trunk@308421 --- lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp') diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 5689c06042391..a20f474cbf40d 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -417,8 +417,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // the highest demanded bit, we just return the other side. if (DemandedFromOps.isSubsetOf(RHSKnown.Zero)) return I->getOperand(0); - // We can't do this with the LHS for subtraction. - if (I->getOpcode() == Instruction::Add && + // We can't do this with the LHS for subtraction, unless we are only + // demanding the LSB. + if ((I->getOpcode() == Instruction::Add || + DemandedFromOps.isOneValue()) && DemandedFromOps.isSubsetOf(LHSKnown.Zero)) return I->getOperand(1); } -- cgit v1.2.3