diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index 1f89ca635a9..ff682acd3fd 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -1569,7 +1569,37 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { // NOTE: if we wanted to, this is where to detect MIN/MAX } - // NOTE: if we wanted to, this is where to detect ABS + + // Canonicalize select with fcmp to fabs(). -0.0 makes this tricky. We need + // fast-math-flags (nsz) or fsub with +0.0 (not fneg) for this to work. We + // also require nnan because we do not want to unintentionally change the + // sign of a NaN value. + Value *X = FCI->getOperand(0); + FCmpInst::Predicate Pred = FCI->getPredicate(); + if (match(FCI->getOperand(1), m_AnyZeroFP()) && FCI->hasNoNaNs()) { + // (X <= +/-0.0) ? (0.0 - X) : X --> fabs(X) + // (X > +/-0.0) ? X : (0.0 - X) --> fabs(X) + if ((X == FalseVal && match(TrueVal, m_FSub(m_Zero(), m_Specific(X))) && + Pred == FCmpInst::FCMP_OLE) || + (X == TrueVal && match(FalseVal, m_FSub(m_Zero(), m_Specific(X))) && + Pred == FCmpInst::FCMP_OGT)) { + Value *Fabs = Builder.CreateIntrinsic(Intrinsic::fabs, { X }, FCI); + return replaceInstUsesWith(SI, Fabs); + } + // With nsz: + // (X < +/-0.0) ? -X : X --> fabs(X) + // (X <= +/-0.0) ? -X : X --> fabs(X) + // (X > +/-0.0) ? X : -X --> fabs(X) + // (X >= +/-0.0) ? X : -X --> fabs(X) + if (FCI->hasNoSignedZeros() && + ((X == FalseVal && match(TrueVal, m_FNeg(m_Specific(X))) && + (Pred == FCmpInst::FCMP_OLT || Pred == FCmpInst::FCMP_OLE)) || + (X == TrueVal && match(FalseVal, m_FNeg(m_Specific(X))) && + (Pred == FCmpInst::FCMP_OGT || Pred == FCmpInst::FCMP_OGE)))) { + Value *Fabs = Builder.CreateIntrinsic(Intrinsic::fabs, { X }, FCI); + return replaceInstUsesWith(SI, Fabs); + } + } } // See if we are selecting two values based on a comparison of the two values. |
