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[LoopVectorize] Make collectInLoopReductions more efficient #126769

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merged 1 commit into from
Feb 12, 2025
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[LoopVectorize] Make collectInLoopReductions more efficient #126769

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8 changes: 6 additions & 2 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5260,6 +5260,8 @@ LoopVectorizationCostModel::calculateRegisterUsage(ArrayRef<ElementCount> VFs) {
return TTICapture.getRegUsageForType(VectorType::get(Ty, VF));
};

collectInLoopReductions();

for (unsigned int Idx = 0, Sz = IdxToInstr.size(); Idx < Sz; ++Idx) {
Instruction *I = IdxToInstr[Idx];

Expand All @@ -5276,8 +5278,6 @@ LoopVectorizationCostModel::calculateRegisterUsage(ArrayRef<ElementCount> VFs) {
if (ValuesToIgnore.count(I))
continue;

collectInLoopReductions();

// For each VF find the maximum usage of registers.
for (unsigned J = 0, E = VFs.size(); J < E; ++J) {
// Count the number of registers used, per register class, given all open
Expand Down Expand Up @@ -7008,6 +7008,10 @@ void LoopVectorizationCostModel::collectValuesToIgnore() {
}

void LoopVectorizationCostModel::collectInLoopReductions() {
// Avoid duplicating work finding in-loop reductions.
if (!InLoopReductions.empty())
return;

for (const auto &Reduction : Legal->getReductionVars()) {
PHINode *Phi = Reduction.first;
const RecurrenceDescriptor &RdxDesc = Reduction.second;
Expand Down