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[LoopUnroll] Make use of MaxTripCount for loops with "#pragma unroll" #74703

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Merged
merged 2 commits into from
Dec 8, 2023
Merged

[LoopUnroll] Make use of MaxTripCount for loops with "#pragma unroll" #74703

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0e5655e
[LoopUnroll] Pre-commit test for loop unroll after folding branches i…
xiangzh1 Dec 7, 2023
d0dc993
[LoopUnroll] Unroll small loops with 'pragma unroll' when its trip co…
xiangzh1 Dec 8, 2023
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8 changes: 6 additions & 2 deletions llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -755,7 +755,7 @@ static unsigned getFullUnrollBoostingFactor(const EstimatedUnrollCost &Cost,
static std::optional<unsigned>
shouldPragmaUnroll(Loop *L, const PragmaInfo &PInfo,
const unsigned TripMultiple, const unsigned TripCount,
const UnrollCostEstimator UCE,
unsigned MaxTripCount, const UnrollCostEstimator UCE,
const TargetTransformInfo::UnrollingPreferences &UP) {

// Using unroll pragma
Expand All @@ -776,6 +776,10 @@ shouldPragmaUnroll(Loop *L, const PragmaInfo &PInfo,
if (PInfo.PragmaFullUnroll && TripCount != 0)
return TripCount;

if (PInfo.PragmaEnableUnroll && !TripCount && MaxTripCount &&
MaxTripCount <= UnrollMaxUpperBound)
return MaxTripCount;

// if didn't return until here, should continue to other priorties
return std::nullopt;
}
Expand Down Expand Up @@ -902,7 +906,7 @@ bool llvm::computeUnrollCount(
// 1st priority is unroll count set by "unroll-count" option.
// 2nd priority is unroll count set by pragma.
if (auto UnrollFactor = shouldPragmaUnroll(L, PInfo, TripMultiple, TripCount,
UCE, UP)) {
MaxTripCount, UCE, UP)) {
UP.Count = *UnrollFactor;

if (UserUnrollCount || (PragmaCount > 0)) {
Expand Down
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