diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/GuardWidening.cpp | 36 |
1 files changed, 23 insertions, 13 deletions
diff --git a/llvm/lib/Transforms/Scalar/GuardWidening.cpp b/llvm/lib/Transforms/Scalar/GuardWidening.cpp index d0bd614533d..5ac4374038e 100644 --- a/llvm/lib/Transforms/Scalar/GuardWidening.cpp +++ b/llvm/lib/Transforms/Scalar/GuardWidening.cpp @@ -356,21 +356,31 @@ bool GuardWideningImpl::widenCondCommon(Value *Cond0, Value *Cond1, if (match(Cond0, m_ICmp(Pred0, m_Value(LHS), m_ConstantInt(RHS0))) && match(Cond1, m_ICmp(Pred1, m_Specific(LHS), m_ConstantInt(RHS1)))) { - // TODO: This logic should be generalized and refactored into a new - // Constant::getEquivalentICmp helper. - if (Pred0 == ICmpInst::ICMP_NE && RHS0->isZero()) - Pred0 = ICmpInst::ICMP_UGT; - if (Pred1 == ICmpInst::ICMP_NE && RHS1->isZero()) - Pred1 = ICmpInst::ICMP_UGT; - - if (Pred0 == ICmpInst::ICMP_UGT && Pred1 == ICmpInst::ICMP_UGT) { + ConstantRange CR0 = + ConstantRange::makeExactICmpRegion(Pred0, RHS0->getValue()); + ConstantRange CR1 = + ConstantRange::makeExactICmpRegion(Pred1, RHS1->getValue()); + + // SubsetIntersect is a subset of the actual mathematical intersection of + // CR0 and CR1, while SupersetIntersect is a superset of the the actual + // mathematical intersection. If these two ConstantRanges are equal, then + // we know we were able to represent the actual mathematical intersection + // of CR0 and CR1, and can use the same to generate an icmp instruction. + // + // Given what we're doing here and the semantics of guards, it would + // actually be correct to just use SubsetIntersect, but that may be too + // aggressive in cases we care about. + auto SubsetIntersect = CR0.inverse().unionWith(CR1.inverse()).inverse(); + auto SupersetIntersect = CR0.intersectWith(CR1); + + APInt NewRHSAP; + CmpInst::Predicate Pred; + if (SubsetIntersect == SupersetIntersect && + SubsetIntersect.getEquivalentICmp(Pred, NewRHSAP)) { if (InsertPt) { - ConstantInt *NewRHS = - RHS0->getValue().ugt(RHS1->getValue()) ? RHS0 : RHS1; - Result = new ICmpInst(InsertPt, ICmpInst::ICMP_UGT, LHS, NewRHS, - "wide.chk"); + ConstantInt *NewRHS = ConstantInt::get(Cond0->getContext(), NewRHSAP); + Result = new ICmpInst(InsertPt, Pred, LHS, NewRHS, "wide.chk"); } - return true; } } |
