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[NFC][LLVM] Code cleanup in MisExpect.cpp #162695

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Merged
merged 1 commit into from
Oct 10, 2025
Merged

[NFC][LLVM] Code cleanup in MisExpect.cpp #162695

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22 changes: 10 additions & 12 deletions llvm/include/llvm/Transforms/Utils/MisExpect.h
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,7 @@
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"

namespace llvm {
namespace misexpect {
namespace llvm::misexpect {

/// checkBackendInstrumentation - compares PGO counters to the thresholds used
/// for llvm.expect and warns if the PGO counters are outside of the expected
Expand All @@ -34,8 +33,8 @@ namespace misexpect {
///
/// \param I The Instruction being checked
/// \param RealWeights A vector of profile weights for each target block
void checkBackendInstrumentation(Instruction &I,
const llvm::ArrayRef<uint32_t> RealWeights);
void checkBackendInstrumentation(const Instruction &I,
ArrayRef<uint32_t> RealWeights);

/// checkFrontendInstrumentation - compares PGO counters to the thresholds used
/// for llvm.expect and warns if the PGO counters are outside of the expected
Expand All @@ -48,8 +47,8 @@ void checkBackendInstrumentation(Instruction &I,
/// \param I The Instruction being checked
/// \param ExpectedWeights A vector of the expected weights for each target
/// block, this determines the threshold values used when emitting diagnostics
void checkFrontendInstrumentation(Instruction &I,
const ArrayRef<uint32_t> ExpectedWeights);
void checkFrontendInstrumentation(const Instruction &I,
ArrayRef<uint32_t> ExpectedWeights);

/// veryifyMisExpect - compares RealWeights to the thresholds used
/// for llvm.expect and warns if the PGO counters are outside of the expected
Expand All @@ -58,8 +57,8 @@ void checkFrontendInstrumentation(Instruction &I,
/// \param I The Instruction being checked
/// \param RealWeights A vector of profile weights from the profile data
/// \param ExpectedWeights A vector of the weights attatch by llvm.expect
void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
const ArrayRef<uint32_t> ExpectedWeights);
void verifyMisExpect(const Instruction &I, ArrayRef<uint32_t> RealWeights,
ArrayRef<uint32_t> ExpectedWeights);

/// checkExpectAnnotations - compares PGO counters to the thresholds used
/// for llvm.expect and warns if the PGO counters are outside of the expected
Expand All @@ -72,11 +71,10 @@ void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
/// \param I The Instruction being checked
/// \param ExistingWeights A vector of profile weights for each target block
/// \param IsFrontend A boolean describing if this is Frontend instrumentation
void checkExpectAnnotations(Instruction &I,
const ArrayRef<uint32_t> ExistingWeights,
void checkExpectAnnotations(const Instruction &I,
ArrayRef<uint32_t> ExistingWeights,
bool IsFrontend);

} // namespace misexpect
} // namespace llvm
} // namespace llvm::misexpect

#endif
61 changes: 22 additions & 39 deletions llvm/lib/Transforms/Utils/MisExpect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -48,8 +48,6 @@
using namespace llvm;
using namespace misexpect;

namespace llvm {

// Command line option to enable/disable the warning when profile data suggests
// a mismatch with the use of the llvm.expect intrinsic
static cl::opt<bool> PGOWarnMisExpect(
Expand All @@ -63,22 +61,18 @@ static cl::opt<uint32_t> MisExpectTolerance(
cl::desc("Prevents emitting diagnostics when profile counts are "
"within N% of the threshold.."));

} // namespace llvm

namespace {

bool isMisExpectDiagEnabled(LLVMContext &Ctx) {
static bool isMisExpectDiagEnabled(const LLVMContext &Ctx) {
return PGOWarnMisExpect || Ctx.getMisExpectWarningRequested();
}

uint32_t getMisExpectTolerance(LLVMContext &Ctx) {
static uint32_t getMisExpectTolerance(const LLVMContext &Ctx) {
return std::max(static_cast<uint32_t>(MisExpectTolerance),
Ctx.getDiagnosticsMisExpectTolerance());
}

Instruction *getInstCondition(Instruction *I) {
static const Instruction *getInstCondition(const Instruction *I) {
assert(I != nullptr && "MisExpect target Instruction cannot be nullptr");
Instruction *Ret = nullptr;
const Instruction *Ret = nullptr;
if (auto *B = dyn_cast<BranchInst>(I)) {
Ret = dyn_cast<Instruction>(B->getCondition());
}
Expand All @@ -97,29 +91,25 @@ Instruction *getInstCondition(Instruction *I) {
return Ret ? Ret : I;
}

void emitMisexpectDiagnostic(Instruction *I, LLVMContext &Ctx,
uint64_t ProfCount, uint64_t TotalCount) {
static void emitMisexpectDiagnostic(const Instruction *I, LLVMContext &Ctx,
uint64_t ProfCount, uint64_t TotalCount) {
double PercentageCorrect = (double)ProfCount / TotalCount;
auto PerString =
formatv("{0:P} ({1} / {2})", PercentageCorrect, ProfCount, TotalCount);
auto RemStr = formatv(
"Potential performance regression from use of the llvm.expect intrinsic: "
"Annotation was correct on {0} of profiled executions.",
PerString);
Instruction *Cond = getInstCondition(I);
const Instruction *Cond = getInstCondition(I);
if (isMisExpectDiagEnabled(Ctx))
Ctx.diagnose(DiagnosticInfoMisExpect(Cond, Twine(PerString)));
OptimizationRemarkEmitter ORE(I->getParent()->getParent());
ORE.emit(OptimizationRemark(DEBUG_TYPE, "misexpect", Cond) << RemStr.str());
}

} // namespace

namespace llvm {
namespace misexpect {

void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
ArrayRef<uint32_t> ExpectedWeights) {
void misexpect::verifyMisExpect(const Instruction &I,
ArrayRef<uint32_t> RealWeights,
ArrayRef<uint32_t> ExpectedWeights) {
// To determine if we emit a diagnostic, we need to compare the branch weights
// from the profile to those added by the llvm.expect intrinsic.
// So first, we extract the "likely" and "unlikely" weights from
Expand All @@ -128,15 +118,13 @@ void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
uint64_t LikelyBranchWeight = 0,
UnlikelyBranchWeight = std::numeric_limits<uint32_t>::max();
size_t MaxIndex = 0;
for (size_t Idx = 0, End = ExpectedWeights.size(); Idx < End; Idx++) {
uint32_t V = ExpectedWeights[Idx];
for (const auto &[Idx, V] : enumerate(ExpectedWeights)) {
if (LikelyBranchWeight < V) {
LikelyBranchWeight = V;
MaxIndex = Idx;
}
if (UnlikelyBranchWeight > V) {
if (UnlikelyBranchWeight > V)
UnlikelyBranchWeight = V;
}
}

const uint64_t ProfiledWeight = RealWeights[MaxIndex];
Expand All @@ -161,7 +149,7 @@ void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
uint64_t ScaledThreshold = LikelyProbablilty.scale(RealWeightsTotal);

// clamp tolerance range to [0, 100)
auto Tolerance = getMisExpectTolerance(I.getContext());
uint32_t Tolerance = getMisExpectTolerance(I.getContext());
Tolerance = std::clamp(Tolerance, 0u, 99u);

// Allow users to relax checking by N% i.e., if they use a 5% tolerance,
Expand All @@ -175,8 +163,8 @@ void verifyMisExpect(Instruction &I, ArrayRef<uint32_t> RealWeights,
RealWeightsTotal);
}

void checkBackendInstrumentation(Instruction &I,
const ArrayRef<uint32_t> RealWeights) {
void misexpect::checkBackendInstrumentation(const Instruction &I,
ArrayRef<uint32_t> RealWeights) {
// Backend checking assumes any existing weight comes from an `llvm.expect`
// intrinsic. However, SampleProfiling + ThinLTO add branch weights multiple
// times, leading to an invalid assumption in our checking. Backend checks
Expand All @@ -190,24 +178,19 @@ void checkBackendInstrumentation(Instruction &I,
verifyMisExpect(I, RealWeights, ExpectedWeights);
}

void checkFrontendInstrumentation(Instruction &I,
const ArrayRef<uint32_t> ExpectedWeights) {
void misexpect::checkFrontendInstrumentation(
const Instruction &I, ArrayRef<uint32_t> ExpectedWeights) {
SmallVector<uint32_t> RealWeights;
if (!extractBranchWeights(I, RealWeights))
return;
verifyMisExpect(I, RealWeights, ExpectedWeights);
}

void checkExpectAnnotations(Instruction &I,
const ArrayRef<uint32_t> ExistingWeights,
bool IsFrontend) {
if (IsFrontend) {
void misexpect::checkExpectAnnotations(const Instruction &I,
ArrayRef<uint32_t> ExistingWeights,
bool IsFrontend) {
if (IsFrontend)
checkFrontendInstrumentation(I, ExistingWeights);
} else {
else
checkBackendInstrumentation(I, ExistingWeights);
}
}

} // namespace misexpect
} // namespace llvm
#undef DEBUG_TYPE