From b0b2bf3b5da950679db1431aae431a6dedea2245 Mon Sep 17 00:00:00 2001 From: Max Kazantsev Date: Thu, 27 May 2021 11:47:30 +0700 Subject: [PATCH] [NFCI][LoopDeletion] Only query SCEV about loop successor if another successor is also in loop --- llvm/lib/Transforms/Scalar/LoopDeletion.cpp | 23 ++++++++++++--------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp index 41be776ec141..14eb07ab17e6 100644 --- a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp +++ b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp @@ -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); }