diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 83054588a9a..052cb4ab675 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1847,13 +1847,27 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) { if (I.hasNoSignedZeros() && match(Op0, m_PosZeroFP())) return BinaryOperator::CreateFNegFMF(Op1, &I); + Value *X, *Y; + 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. + // -(X * C) --> X * (-C) + if (match(&I, m_FNeg(m_OneUse(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)))))) + 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)))))) + return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I); + // If Op0 is not -0.0 or we can ignore -0.0: Z - (X - Y) --> Z + (Y - X) // Canonicalize to fadd to make analysis easier. // This can also help codegen because fadd is commutative. // Note that if this fsub was really an fneg, the fadd with -0.0 will get // killed later. We still limit that particular transform with 'hasOneUse' // because an fneg is assumed better/cheaper than a generic fsub. - Value *X, *Y; if (I.hasNoSignedZeros() || CannotBeNegativeZero(Op0, SQ.TLI)) { if (match(Op1, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) { Value *NewSub = Builder.CreateFSubFMF(Y, X, &I); @@ -1869,7 +1883,6 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) { // X - C --> X + (-C) // But don't transform constant expressions because there's an inverse fold // for X + (-Y) --> X - Y. - Constant *C; if (match(Op1, m_Constant(C)) && !isa<ConstantExpr>(Op1)) return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I); |
