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[NARY-REASSOCIATE][NFC] Simplify min/max handling 

In order to explore different variants of reassociation current implementation uses "swap in a loop" approach. Unfortunately, the implementation is more complicated than it could be. This is an attempt to streamline the code. New approach is to extract core functionality into a helper function and call it explicitly as many times as required.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D112128
This commit is contained in:
Evgeniy Brevnov 2021-10-20 16:42:19 +07:00
parent 36ec848dc7
commit 1a8ec24efb
1 changed files with 52 additions and 49 deletions
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101
llvm/lib/Transforms/Scalar/NaryReassociate.cpp
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@ -282,8 +282,12 @@ NaryReassociatePass::matchAndReassociateMinOrMax(Instruction *I,
m_Value(LHS), m_Value(RHS)); m_Value(LHS), m_Value(RHS));
if (match(I, MinMaxMatcher)) { if (match(I, MinMaxMatcher)) {
OrigSCEV = SE->getSCEV(I); OrigSCEV = SE->getSCEV(I);
return dyn_cast_or_null<Instruction>( if (auto *NewMinMax = dyn_cast_or_null<Instruction>(
tryReassociateMinOrMax(I, MinMaxMatcher, LHS, RHS)); tryReassociateMinOrMax(I, MinMaxMatcher, LHS, RHS)))
return NewMinMax;
if (auto *NewMinMax = dyn_cast_or_null<Instruction>(
tryReassociateMinOrMax(I, MinMaxMatcher, RHS, LHS)))
return NewMinMax;
} }
return nullptr; return nullptr;
} }
@ -596,61 +600,60 @@ Value *NaryReassociatePass::tryReassociateMinOrMax(Instruction *I,
Value *LHS, Value *RHS) { Value *LHS, Value *RHS) {
Value *A = nullptr, *B = nullptr; Value *A = nullptr, *B = nullptr;
MaxMinT m_MaxMin(m_Value(A), m_Value(B)); MaxMinT m_MaxMin(m_Value(A), m_Value(B));
for (unsigned int i = 0; i < 2; ++i) {
if (!LHS->hasNUsesOrMore(3) && match(LHS, m_MaxMin)) {
Value *C = RHS;
const SCEV *AExpr = SE->getSCEV(A), *BExpr = SE->getSCEV(B);
const SCEV *CExpr = SE->getSCEV(C);
for (unsigned int j = 0; j < 2; ++j) {
if (j == 0) {
if (BExpr == CExpr)
continue;
// Transform 'I = (A op B) op C' to 'I = (A op C) op B' on the
// first iteration.
std::swap(BExpr, CExpr);
std::swap(B, C);
} else {
if (AExpr == CExpr)
continue;
// Transform 'I = (A op C) op B' to 'I = (B op C) op A' on the second
// iteration.
std::swap(AExpr, CExpr);
std::swap(A, C);
}
// The optimization is profitable only if LHS can be removed in the end. if (LHS->hasNUsesOrMore(3) ||
// In other words LHS should be used (directly or indirectly) by I only. // The optimization is profitable only if LHS can be removed in the end.
if (llvm::any_of(LHS->users(), [&](auto *U) { // In other words LHS should be used (directly or indirectly) by I only.
return U != I && !(U->hasOneUser() && *U->users().begin() == I); llvm::any_of(LHS->users(),
})) [&](auto *U) {
continue; return U != I &&
!(U->hasOneUser() && *U->users().begin() == I);
}) ||
!match(LHS, m_MaxMin))
return nullptr;
SCEVExpander Expander(*SE, *DL, "nary-reassociate"); auto tryCombination = [&](Value *A, const SCEV *AExpr, Value *B,
SmallVector<const SCEV *, 2> Ops1{ BExpr, AExpr }; const SCEV *BExpr, Value *C,
const SCEVTypes SCEVType = convertToSCEVype(m_MaxMin); const SCEV *CExpr) -> Value * {
const SCEV *R1Expr = SE->getMinMaxExpr(SCEVType, Ops1); SmallVector<const SCEV *, 2> Ops1{BExpr, AExpr};
const SCEVTypes SCEVType = convertToSCEVype(m_MaxMin);
const SCEV *R1Expr = SE->getMinMaxExpr(SCEVType, Ops1);
Instruction *R1MinMax = findClosestMatchingDominator(R1Expr, I); Instruction *R1MinMax = findClosestMatchingDominator(R1Expr, I);
if (!R1MinMax) if (!R1MinMax)
continue; return nullptr;
LLVM_DEBUG(dbgs() << "NARY: Found common sub-expr: " << *R1MinMax LLVM_DEBUG(dbgs() << "NARY: Found common sub-expr: " << *R1MinMax << "\n");
<< "\n");
SmallVector<const SCEV *, 2> Ops2{SE->getUnknown(C), SmallVector<const SCEV *, 2> Ops2{SE->getUnknown(C),
SE->getUnknown(R1MinMax)}; SE->getUnknown(R1MinMax)};
const SCEV *R2Expr = SE->getMinMaxExpr(SCEVType, Ops2); const SCEV *R2Expr = SE->getMinMaxExpr(SCEVType, Ops2);
Value *NewMinMax = Expander.expandCodeFor(R2Expr, I->getType(), I); SCEVExpander Expander(*SE, *DL, "nary-reassociate");
NewMinMax->setName(Twine(I->getName()).concat(".nary")); Value *NewMinMax = Expander.expandCodeFor(R2Expr, I->getType(), I);
NewMinMax->setName(Twine(I->getName()).concat(".nary"));
LLVM_DEBUG(dbgs() << "NARY: Deleting: " << *I << "\n" LLVM_DEBUG(dbgs() << "NARY: Deleting: " << *I << "\n"
<< "NARY: Inserting: " << *NewMinMax << "\n"); << "NARY: Inserting: " << *NewMinMax << "\n");
return NewMinMax; return NewMinMax;
} };
}
std::swap(LHS, RHS); const SCEV *AExpr = SE->getSCEV(A);
const SCEV *BExpr = SE->getSCEV(B);
const SCEV *RHSExpr = SE->getSCEV(RHS);
if (BExpr != RHSExpr) {
// Try (A op RHS) op B
if (auto *NewMinMax = tryCombination(A, AExpr, RHS, RHSExpr, B, BExpr))
return NewMinMax;
} }
if (AExpr != RHSExpr) {
// Try (RHS op B) op A
if (auto *NewMinMax = tryCombination(RHS, RHSExpr, B, BExpr, A, AExpr))
return NewMinMax;
}
return nullptr; return nullptr;
} }