diff options
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineSelect.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineSelect.cpp | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp index 7807d9a..2fc9325 100644 --- a/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -539,9 +539,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { !CFPf->getValueAPF().isZero())) return ReplaceInstUsesWith(SI, FalseVal); } - // Transform (X != Y) ? X : Y -> X - if (FCI->getPredicate() == FCmpInst::FCMP_ONE) + // Transform (X une Y) ? X : Y -> X + if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { + // This is not safe in general for floating point: + // consider X== -0, Y== +0. + // It becomes safe if either operand is a nonzero constant. + ConstantFP *CFPt, *CFPf; + if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && + !CFPt->getValueAPF().isZero()) || + ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && + !CFPf->getValueAPF().isZero())) return ReplaceInstUsesWith(SI, TrueVal); + } // NOTE: if we wanted to, this is where to detect MIN/MAX } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ @@ -557,9 +566,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { !CFPf->getValueAPF().isZero())) return ReplaceInstUsesWith(SI, FalseVal); } - // Transform (X != Y) ? Y : X -> Y - if (FCI->getPredicate() == FCmpInst::FCMP_ONE) - return ReplaceInstUsesWith(SI, TrueVal); + // Transform (X une Y) ? Y : X -> Y + if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { + // This is not safe in general for floating point: + // consider X== -0, Y== +0. + // It becomes safe if either operand is a nonzero constant. + ConstantFP *CFPt, *CFPf; + if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && + !CFPt->getValueAPF().isZero()) || + ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && + !CFPf->getValueAPF().isZero())) + return ReplaceInstUsesWith(SI, TrueVal); + } // NOTE: if we wanted to, this is where to detect MIN/MAX } // NOTE: if we wanted to, this is where to detect ABS |
