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[NFCI][LoopDeletion] Only query SCEV about loop successor if another successor is also in loop

This commit is contained in:
Max Kazantsev 2021-05-27 11:47:30 +07:00
parent d82f2a123f
commit b0b2bf3b5d
1 changed files with 13 additions and 10 deletions
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23
llvm/lib/Transforms/Scalar/LoopDeletion.cpp
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@ -267,10 +267,10 @@ static bool canProveExitOnFirstIteration(Loop *L, DominatorTree &DT,
ICmpInst::Predicate Pred;
Value *LHS, *RHS;
const BasicBlock *IfTrue, *IfFalse;
auto *Term = BB->getTerminator();
// TODO: Handle switches.
if (!match(BB->getTerminator(),
m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)),
m_BasicBlock(IfTrue), m_BasicBlock(IfFalse)))) {
if (!match(Term, m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)),
m_BasicBlock(IfTrue), m_BasicBlock(IfFalse)))) {
MarkAllSuccessorsLive(BB);
continue;
}
@ -283,13 +283,16 @@ static bool canProveExitOnFirstIteration(Loop *L, DominatorTree &DT,
// Can we prove constant true or false for this condition?
const SCEV *LHSS = getSCEVOnFirstIteration(LHS, L, SE, FirstIterSCEV);
const SCEV *RHSS = getSCEVOnFirstIteration(RHS, L, SE, FirstIterSCEV);
// TODO: isKnownPredicateAt is more powerful, but it's too compile time
// consuming. So we avoid using it here.
if (SE.isKnownPredicate(Pred, LHSS, RHSS))
MarkLiveEdge(BB, BB->getTerminator()->getSuccessor(0));
else if (SE.isKnownPredicate(ICmpInst::getInversePredicate(Pred), LHSS,
RHSS))
MarkLiveEdge(BB, BB->getTerminator()->getSuccessor(1));
// Only query for liveness of in-loop edge if another successor is also
// in-loop.
// TODO: isKnownPredicateAt is more powerful, but it's too compile time
// consuming. So we avoid using it here.
if (L->contains(Term->getSuccessor(1)) &&
SE.isKnownPredicate(Pred, LHSS, RHSS))
MarkLiveEdge(BB, Term->getSuccessor(0));
else if (L->contains(Term->getSuccessor(0)) &&
SE.isKnownPredicate(ICmpInst::getInversePredicate(Pred), LHSS,
RHSS)) MarkLiveEdge(BB, Term->getSuccessor(1));
else
MarkAllSuccessorsLive(BB);
}