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[LoopPeel][NFC] Exit early if there is no room for peeling 

Differential Revision: https://reviews.llvm.org/D123864
This commit is contained in:
Igor Kudrin 2022-04-26 18:43:56 +04:00
parent c89433d7fa
commit c71890e158
1 changed files with 39 additions and 37 deletions
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76
llvm/lib/Transforms/Utils/LoopPeel.cpp
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@ -386,6 +386,10 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
if (!PP.AllowPeeling)
return;
// Check that we can peel at least one iteration.
if (2 * LoopSize > Threshold)
return;
unsigned AlreadyPeeled = 0;
if (auto Peeled = getOptionalIntLoopAttribute(L, PeeledCountMetaData))
AlreadyPeeled = *Peeled;
@ -398,47 +402,45 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
// which every Phi is guaranteed to become an invariant, and try to peel the
// maximum number of iterations among these values, thus turning all those
// Phis into invariants.
// First, check that we can peel at least one iteration.
if (2 * LoopSize <= Threshold && UnrollPeelMaxCount > 0) {
// Store the pre-calculated values here.
SmallDenseMap<PHINode *, Optional<unsigned> > IterationsToInvariance;
// Now go through all Phis to calculate their the number of iterations they
// need to become invariants.
// Start the max computation with the PP.PeelCount value set by the target
// in TTI.getPeelingPreferences or by the flag -unroll-peel-count.
unsigned DesiredPeelCount = TargetPeelCount;
BasicBlock *BackEdge = L->getLoopLatch();
assert(BackEdge && "Loop is not in simplified form?");
for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {
PHINode *Phi = cast<PHINode>(&*BI);
auto ToInvariance = calculateIterationsToInvariance(
Phi, L, BackEdge, IterationsToInvariance);
if (ToInvariance)
DesiredPeelCount = std::max(DesiredPeelCount, *ToInvariance);
}
// Pay respect to limitations implied by loop size and the max peel count.
unsigned MaxPeelCount = UnrollPeelMaxCount;
MaxPeelCount = std::min(MaxPeelCount, Threshold / LoopSize - 1);
// Store the pre-calculated values here.
SmallDenseMap<PHINode *, Optional<unsigned>> IterationsToInvariance;
// Now go through all Phis to calculate their the number of iterations they
// need to become invariants.
// Start the max computation with the PP.PeelCount value set by the target
// in TTI.getPeelingPreferences or by the flag -unroll-peel-count.
unsigned DesiredPeelCount = TargetPeelCount;
BasicBlock *BackEdge = L->getLoopLatch();
assert(BackEdge && "Loop is not in simplified form?");
for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {
PHINode *Phi = cast<PHINode>(&*BI);
auto ToInvariance = calculateIterationsToInvariance(Phi, L, BackEdge,
IterationsToInvariance);
if (ToInvariance)
DesiredPeelCount = std::max(DesiredPeelCount, *ToInvariance);
}
DesiredPeelCount = std::max(DesiredPeelCount,
countToEliminateCompares(*L, MaxPeelCount, SE));
// Pay respect to limitations implied by loop size and the max peel count.
unsigned MaxPeelCount = UnrollPeelMaxCount;
MaxPeelCount = std::min(MaxPeelCount, Threshold / LoopSize - 1);
if (DesiredPeelCount == 0)
DesiredPeelCount = peelToTurnInvariantLoadsDerefencebale(*L, DT);
DesiredPeelCount = std::max(DesiredPeelCount,
countToEliminateCompares(*L, MaxPeelCount, SE));
if (DesiredPeelCount > 0) {
DesiredPeelCount = std::min(DesiredPeelCount, MaxPeelCount);
// Consider max peel count limitation.
assert(DesiredPeelCount > 0 && "Wrong loop size estimation?");
if (DesiredPeelCount + AlreadyPeeled <= UnrollPeelMaxCount) {
LLVM_DEBUG(dbgs() << "Peel " << DesiredPeelCount
<< " iteration(s) to turn"
<< " some Phis into invariants.\n");
PP.PeelCount = DesiredPeelCount;
PP.PeelProfiledIterations = false;
return;
}
if (DesiredPeelCount == 0)
DesiredPeelCount = peelToTurnInvariantLoadsDerefencebale(*L, DT);
if (DesiredPeelCount > 0) {
DesiredPeelCount = std::min(DesiredPeelCount, MaxPeelCount);
// Consider max peel count limitation.
assert(DesiredPeelCount > 0 && "Wrong loop size estimation?");
if (DesiredPeelCount + AlreadyPeeled <= UnrollPeelMaxCount) {
LLVM_DEBUG(dbgs() << "Peel " << DesiredPeelCount
<< " iteration(s) to turn"
<< " some Phis into invariants.\n");
PP.PeelCount = DesiredPeelCount;
PP.PeelProfiledIterations = false;
return;
}
}