diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 2a77f56e569..2e0d3bf0a24 100644 --- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -2125,27 +2125,30 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) { /// This eliminates floating-point negation in either 'fneg(X)' or /// 'fsub(-0.0, X)' form by combining into a constant operand. static Instruction *foldFNegIntoConstant(Instruction &I) { + // This is limited with one-use because fneg is assumed better for + // reassociation and cheaper in codegen than fmul/fdiv. + // TODO: Should the m_OneUse restriction be removed? + Instruction *FNegOp; + if (!match(&I, m_FNeg(m_OneUse(m_Instruction(FNegOp))))) + return nullptr; + Value *X; Constant *C; - // Fold negation into constant operand. This is limited with one-use because - // fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv. + // Fold negation into constant operand. // -(X * C) --> X * (-C) - // FIXME: It's arguable whether these should be m_OneUse or not. The current - // belief is that the FNeg allows for better reassociation opportunities. - if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C)))))) + if (match(FNegOp, m_FMul(m_Value(X), m_Constant(C)))) return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I); // -(X / C) --> X / (-C) - if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C)))))) + if (match(FNegOp, m_FDiv(m_Value(X), m_Constant(C)))) return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I); // -(C / X) --> (-C) / X - if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X)))))) + if (match(FNegOp, m_FDiv(m_Constant(C), m_Value(X)))) return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I); // With NSZ [ counter-example with -0.0: -(-0.0 + 0.0) != 0.0 + -0.0 ]: // -(X + C) --> -X + -C --> -C - X - if (I.hasNoSignedZeros() && - match(&I, m_FNeg(m_OneUse(m_FAdd(m_Value(X), m_Constant(C)))))) + if (I.hasNoSignedZeros() && match(FNegOp, m_FAdd(m_Value(X), m_Constant(C)))) return BinaryOperator::CreateFSubFMF(ConstantExpr::getFNeg(C), X, &I); return nullptr;