diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 7f152aac52d..a301d9eef60 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -213,6 +213,25 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I)) return FoldedMul; + // TODO: This is a specific form of a much more general pattern. + // We could detect a select with any binop identity constant, or we + // could use SimplifyBinOp to see if either arm of the select reduces. + // But that needs to be done carefully and/or while removing potential + // reverse canonicalizations as in InstCombiner::foldSelectIntoOp(). + // mul (select Cond, 1, -1), Op1 --> select Cond, Op1, -Op1 + // mul (select Cond, -1, 1), Op1 --> select Cond, -Op1, Op1 + // mul Op0, (select Cond, 1, -1) --> select Cond, Op0, -Op0 + // mul Op0, (select Cond, -1, 1) --> select Cond, -Op0, Op0 + Value *Cond; + if (match(Op0, m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())))) + return SelectInst::Create(Cond, Op1, Builder.CreateNeg(Op1)); + if (match(Op0, m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())))) + return SelectInst::Create(Cond, Builder.CreateNeg(Op1), Op1); + if (match(Op1, m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())))) + return SelectInst::Create(Cond, Op0, Builder.CreateNeg(Op0)); + if (match(Op1, m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())))) + return SelectInst::Create(Cond, Builder.CreateNeg(Op0), Op0); + // Simplify mul instructions with a constant RHS. if (isa<Constant>(Op1)) { // Canonicalize (X+C1)*CI -> X*CI+C1*CI. |
