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[IRCE] consolidate profitability check 

Use BFI if it is available and BPI otherwise.
This is a promised follow-up after D89541.

Reviewers: ebrevnov, mkazantsev
Reviewed By: ebrevnov
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D89773
This commit is contained in:
Serguei Katkov 2020-10-20 13:28:20 +07:00
parent 5b68772ca9
commit 75d0e0cd5f
1 changed files with 43 additions and 28 deletions
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69
llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
View File

@ -233,6 +233,8 @@ public:
SmallVectorImpl<InductiveRangeCheck> &Checks);
};
struct LoopStructure;
class InductiveRangeCheckElimination {
ScalarEvolution &SE;
BranchProbabilityInfo *BPI;
@ -243,6 +245,10 @@ class InductiveRangeCheckElimination {
llvm::Optional<llvm::function_ref<llvm::BlockFrequencyInfo &()> >;
GetBFIFunc GetBFI;
// Returns true if it is profitable to do a transform basing on estimation of
// number of iterations.
bool isProfitableToTransform(const Loop &L, LoopStructure &LS);
public:
InductiveRangeCheckElimination(ScalarEvolution &SE,
BranchProbabilityInfo *BPI, DominatorTree &DT,
@ -505,9 +511,8 @@ struct LoopStructure {
return Result;
}
static Optional<LoopStructure> parseLoopStructure(ScalarEvolution &,
BranchProbabilityInfo *BPI,
Loop &, const char *&);
static Optional<LoopStructure> parseLoopStructure(ScalarEvolution &, Loop &,
const char *&);
};
/// This class is used to constrain loops to run within a given iteration space.
@ -751,8 +756,7 @@ static bool isSafeIncreasingBound(const SCEV *Start,
}
Optional<LoopStructure>
LoopStructure::parseLoopStructure(ScalarEvolution &SE,
BranchProbabilityInfo *BPI, Loop &L,
LoopStructure::parseLoopStructure(ScalarEvolution &SE, Loop &L,
const char *&FailureReason) {
if (!L.isLoopSimplifyForm()) {
FailureReason = "loop not in LoopSimplify form";
@ -787,16 +791,6 @@ LoopStructure::parseLoopStructure(ScalarEvolution &SE,
unsigned LatchBrExitIdx = LatchBr->getSuccessor(0) == Header ? 1 : 0;
BranchProbability ExitProbability =
BPI ? BPI->getEdgeProbability(LatchBr->getParent(), LatchBrExitIdx)
: BranchProbability::getZero();
if (!SkipProfitabilityChecks &&
ExitProbability > BranchProbability(1, MaxExitProbReciprocal)) {
FailureReason = "short running loop, not profitable";
return None;
}
ICmpInst *ICI = dyn_cast<ICmpInst>(LatchBr->getCondition());
if (!ICI || !isa<IntegerType>(ICI->getOperand(0)->getType())) {
FailureReason = "latch terminator branch not conditional on integral icmp";
@ -1855,6 +1849,37 @@ bool IRCELegacyPass::runOnFunction(Function &F) {
return Changed;
}
bool
InductiveRangeCheckElimination::isProfitableToTransform(const Loop &L,
LoopStructure &LS) {
if (SkipProfitabilityChecks)
return true;
if (GetBFI.hasValue()) {
BlockFrequencyInfo &BFI = (*GetBFI)();
uint64_t hFreq = BFI.getBlockFreq(LS.Header).getFrequency();
uint64_t phFreq = BFI.getBlockFreq(L.getLoopPreheader()).getFrequency();
if (phFreq != 0 && hFreq != 0 && (hFreq / phFreq < MinRuntimeIterations)) {
LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
<< "the estimated number of iterations basing on "
"frequency info is " << (hFreq / phFreq) << "\n";);
return false;
}
return true;
}
if (!BPI)
return true;
BranchProbability ExitProbability =
BPI->getEdgeProbability(LS.Latch, LS.LatchBrExitIdx);
if (ExitProbability > BranchProbability(1, MaxExitProbReciprocal)) {
LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
<< "the exit probability is too big " << ExitProbability
<< "\n";);
return false;
}
return true;
}
bool InductiveRangeCheckElimination::run(
Loop *L, function_ref<void(Loop *, bool)> LPMAddNewLoop) {
if (L->getBlocks().size() >= LoopSizeCutoff) {
@ -1894,25 +1919,15 @@ bool InductiveRangeCheckElimination::run(
const char *FailureReason = nullptr;
Optional<LoopStructure> MaybeLoopStructure =
LoopStructure::parseLoopStructure(SE, BPI, *L, FailureReason);
LoopStructure::parseLoopStructure(SE, *L, FailureReason);
if (!MaybeLoopStructure.hasValue()) {
LLVM_DEBUG(dbgs() << "irce: could not parse loop structure: "
<< FailureReason << "\n";);
return false;
}
LoopStructure LS = MaybeLoopStructure.getValue();
// Profitability check.
if (!SkipProfitabilityChecks && GetBFI.hasValue()) {
BlockFrequencyInfo &BFI = (*GetBFI)();
uint64_t hFreq = BFI.getBlockFreq(LS.Header).getFrequency();
uint64_t phFreq = BFI.getBlockFreq(Preheader).getFrequency();
if (phFreq != 0 && hFreq != 0 && (hFreq / phFreq < MinRuntimeIterations)) {
LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
<< "the estimated number of iterations basing on "
"frequency info is " << (hFreq / phFreq) << "\n";);
if (!isProfitableToTransform(*L, LS))
return false;
}
}
const SCEVAddRecExpr *IndVar =
cast<SCEVAddRecExpr>(SE.getMinusSCEV(SE.getSCEV(LS.IndVarBase), SE.getSCEV(LS.IndVarStep)));