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[DA] Improve code in getSplitIteration (NFC) #146137

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Merged
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Jun 30, 2025
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[DA] Improve code in getSplitIteration (NFC) #146137

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112 changes: 55 additions & 57 deletions llvm/lib/Analysis/DependenceAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4188,67 +4188,65 @@ const SCEV *DependenceInfo::getSplitIteration(const Dependence &Dep,
}
}

if (Coupled.count()) {
// test coupled subscript groups
SmallVector<Constraint, 4> Constraints(MaxLevels + 1);
for (unsigned II = 0; II <= MaxLevels; ++II)
Constraints[II].setAny(SE);
for (unsigned SI : Coupled.set_bits()) {
SmallBitVector Group(Pair[SI].Group);
SmallBitVector Sivs(Pairs);
SmallBitVector Mivs(Pairs);
SmallBitVector ConstrainedLevels(MaxLevels + 1);
for (unsigned SJ : Group.set_bits()) {
if (Pair[SJ].Classification == Subscript::SIV)
Sivs.set(SJ);
else
Mivs.set(SJ);
assert(!Coupled.empty() && "coupled expected non-empty");

// test coupled subscript groups
SmallVector<Constraint, 4> Constraints(MaxLevels + 1);
for (unsigned II = 0; II <= MaxLevels; ++II)
Constraints[II].setAny(SE);
for (unsigned SI : Coupled.set_bits()) {
SmallBitVector Group(Pair[SI].Group);
SmallBitVector Sivs(Pairs);
SmallBitVector Mivs(Pairs);
SmallBitVector ConstrainedLevels(MaxLevels + 1);
for (unsigned SJ : Group.set_bits()) {
if (Pair[SJ].Classification == Subscript::SIV)
Sivs.set(SJ);
else
Mivs.set(SJ);
}
while (Sivs.any()) {
bool Changed = false;
for (unsigned SJ : Sivs.set_bits()) {
// SJ is an SIV subscript that's part of the current coupled group
unsigned Level;
const SCEV *SplitIter = nullptr;
(void)testSIV(Pair[SJ].Src, Pair[SJ].Dst, Level, Result, NewConstraint,
SplitIter);
if (Level == SplitLevel && SplitIter)
return SplitIter;
ConstrainedLevels.set(Level);
if (intersectConstraints(&Constraints[Level], &NewConstraint))
Changed = true;
Sivs.reset(SJ);
}
while (Sivs.any()) {
bool Changed = false;
for (unsigned SJ : Sivs.set_bits()) {
// SJ is an SIV subscript that's part of the current coupled group
unsigned Level;
const SCEV *SplitIter = nullptr;
(void) testSIV(Pair[SJ].Src, Pair[SJ].Dst, Level,
Result, NewConstraint, SplitIter);
if (Level == SplitLevel && SplitIter)
return SplitIter;
ConstrainedLevels.set(Level);
if (intersectConstraints(&Constraints[Level], &NewConstraint))
Changed = true;
Sivs.reset(SJ);
}
if (Changed) {
// propagate, possibly creating new SIVs and ZIVs
for (unsigned SJ : Mivs.set_bits()) {
// SJ is an MIV subscript that's part of the current coupled group
if (propagate(Pair[SJ].Src, Pair[SJ].Dst,
Pair[SJ].Loops, Constraints, Result.Consistent)) {
Pair[SJ].Classification =
classifyPair(Pair[SJ].Src, LI->getLoopFor(Src->getParent()),
Pair[SJ].Dst, LI->getLoopFor(Dst->getParent()),
Pair[SJ].Loops);
switch (Pair[SJ].Classification) {
case Subscript::ZIV:
Mivs.reset(SJ);
break;
case Subscript::SIV:
Sivs.set(SJ);
Mivs.reset(SJ);
break;
case Subscript::RDIV:
case Subscript::MIV:
break;
default:
llvm_unreachable("bad subscript classification");
}
}
}
if (!Changed)
continue;
// propagate, possibly creating new SIVs and ZIVs
for (unsigned SJ : Mivs.set_bits()) {
// SJ is an MIV subscript that's part of the current coupled group
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Perhaps this comment should be moved to the end of the if-statement, or revised to describe the early continue.

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I think SJ is referred to in the next line, so I'd leave this as-is.

if (!propagate(Pair[SJ].Src, Pair[SJ].Dst, Pair[SJ].Loops, Constraints,
Result.Consistent))
continue;
Pair[SJ].Classification = classifyPair(
Pair[SJ].Src, LI->getLoopFor(Src->getParent()), Pair[SJ].Dst,
LI->getLoopFor(Dst->getParent()), Pair[SJ].Loops);
switch (Pair[SJ].Classification) {
case Subscript::ZIV:
Mivs.reset(SJ);
break;
case Subscript::SIV:
Sivs.set(SJ);
Mivs.reset(SJ);
break;
case Subscript::RDIV:
case Subscript::MIV:
break;
default:
llvm_unreachable("bad subscript classification");
}
}
}
}
llvm_unreachable("somehow reached end of routine");
return nullptr;
}
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