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[SCEV] Handle `less` predicates for FoundPred = NE 

Currently these predicates are ignored, yet their handling is
pretty simple. I could not find a single test where it would
actually change something, but it's only because isImpliedCondOperands
is not smart enough to prove it further on. Yet the situation when
we come there with `less` predicate is pretty common.

Differential Revision: https://reviews.llvm.org/D87890
Reviewed By: fhahn
This commit is contained in:
Max Kazantsev 2020-09-22 18:44:18 +07:00
parent a3d0dce260
commit e2703c021d
1 changed files with 15 additions and 0 deletions
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15
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -9758,8 +9758,23 @@ bool ScalarEvolution::isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS,
if (isImpliedCondOperands(Pred, LHS, RHS, V, getConstant(Min)))
return true;
break;
// `LHS < RHS` and `LHS <= RHS` are handled in the same way as `RHS > LHS` and `RHS >= LHS` respectively.
case ICmpInst::ICMP_SLE:
case ICmpInst::ICMP_ULE:
if (isImpliedCondOperands(CmpInst::getSwappedPredicate(Pred), RHS,
LHS, V, getConstant(SharperMin)))
return true;
LLVM_FALLTHROUGH;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_ULT:
if (isImpliedCondOperands(CmpInst::getSwappedPredicate(Pred), RHS,
LHS, V, getConstant(Min)))
return true;
break;
default:
// No change
break;