//===- OptimizationRemarkEmitter.h - Optimization Diagnostic ----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Optimization diagnostic interfaces. It's packaged as an analysis pass so
// that by using this service passes become dependent on BFI as well. BFI is
// used to compute the "hotness" of the diagnostic message.
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_OPTIMIZATIONREMARKEMITTER_H
#define LLVM_ANALYSIS_OPTIMIZATIONREMARKEMITTER_H
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
#include <optional>
namespace llvm {
class Function;
class Value;
/// The optimization diagnostic interface.
///
/// It allows reporting when optimizations are performed and when they are not
/// along with the reasons for it. Hotness information of the corresponding
/// code region can be included in the remark if DiagnosticsHotnessRequested is
/// enabled in the LLVM context.
class OptimizationRemarkEmitter {
public:
OptimizationRemarkEmitter(const Function *F, BlockFrequencyInfo *BFI)
: F(F), BFI(BFI) {}
/// This variant can be used to generate ORE on demand (without the
/// analysis pass).
///
/// Note that this ctor has a very different cost depending on whether
/// F->getContext().getDiagnosticsHotnessRequested() is on or not. If it's off
/// the operation is free.
///
/// Whereas if DiagnosticsHotnessRequested is on, it is fairly expensive
/// operation since BFI and all its required analyses are computed. This is
/// for example useful for CGSCC passes that can't use function analyses
/// passes in the old PM.
OptimizationRemarkEmitter(const Function *F);
OptimizationRemarkEmitter(OptimizationRemarkEmitter &&Arg)
: F(Arg.F), BFI(Arg.BFI) {}
OptimizationRemarkEmitter &operator=(OptimizationRemarkEmitter &&RHS) {
F = RHS.F;
BFI = RHS.BFI;
return *this;
}
/// Handle invalidation events in the new pass manager.
bool invalidate(Function &F, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv);
/// Return true iff at least *some* remarks are enabled.
bool enabled() const {
return F->getContext().getLLVMRemarkStreamer() ||
F->getContext().getDiagHandlerPtr()->isAnyRemarkEnabled();
}
/// Output the remark via the diagnostic handler and to the
/// optimization record file.
void emit(DiagnosticInfoOptimizationBase &OptDiag);
/// Take a lambda that returns a remark which will be emitted. Second
/// argument is only used to restrict this to functions.
template <typename T>
void emit(T RemarkBuilder, decltype(RemarkBuilder()) * = nullptr) {
// Avoid building the remark unless we know there are at least *some*
// remarks enabled. We can't currently check whether remarks are requested
// for the calling pass since that requires actually building the remark.
if (enabled()) {
auto R = RemarkBuilder();
static_assert(
std::is_base_of<DiagnosticInfoOptimizationBase, decltype(R)>::value,
"the lambda passed to emit() must return a remark");
emit((DiagnosticInfoOptimizationBase &)R);
}
}
/// Whether we allow for extra compile-time budget to perform more
/// analysis to produce fewer false positives.
///
/// This is useful when reporting missed optimizations. In this case we can
/// use the extra analysis (1) to filter trivial false positives or (2) to
/// provide more context so that non-trivial false positives can be quickly
/// detected by the user.
bool allowExtraAnalysis(StringRef PassName) const {
return OptimizationRemarkEmitter::allowExtraAnalysis(*F, PassName);
}
static bool allowExtraAnalysis(const Function &F, StringRef PassName) {
return allowExtraAnalysis(F.getContext(), PassName);
}
static bool allowExtraAnalysis(LLVMContext &Ctx, StringRef PassName) {
return Ctx.getLLVMRemarkStreamer() ||
Ctx.getDiagHandlerPtr()->isAnyRemarkEnabled(PassName);
}
private:
const Function *F;
BlockFrequencyInfo *BFI;
/// If we generate BFI on demand, we need to free it when ORE is freed.
std::unique_ptr<BlockFrequencyInfo> OwnedBFI;
/// Compute hotness from IR value (currently assumed to be a block) if PGO is
/// available.
std::optional<uint64_t> computeHotness(const Value *V);
/// Similar but use value from \p OptDiag and update hotness there.
void computeHotness(DiagnosticInfoIROptimization &OptDiag);
/// Only allow verbose messages if we know we're filtering by hotness
/// (BFI is only set in this case).
bool shouldEmitVerbose() { return BFI != nullptr; }
OptimizationRemarkEmitter(const OptimizationRemarkEmitter &) = delete;
void operator=(const OptimizationRemarkEmitter &) = delete;
};
/// Add a small namespace to avoid name clashes with the classes used in
/// the streaming interface. We want these to be short for better
/// write/readability.
namespace ore {
using NV = DiagnosticInfoOptimizationBase::Argument;
using setIsVerbose = DiagnosticInfoOptimizationBase::setIsVerbose;
using setExtraArgs = DiagnosticInfoOptimizationBase::setExtraArgs;
}
/// OptimizationRemarkEmitter legacy analysis pass
///
/// Note that this pass shouldn't generally be marked as preserved by other
/// passes. It's holding onto BFI, so if the pass does not preserve BFI, BFI
/// could be freed.
class OptimizationRemarkEmitterWrapperPass : public FunctionPass {
std::unique_ptr<OptimizationRemarkEmitter> ORE;
public:
OptimizationRemarkEmitterWrapperPass();
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
OptimizationRemarkEmitter &getORE() {
assert(ORE && "pass not run yet");
return *ORE;
}
static char ID;
};
class OptimizationRemarkEmitterAnalysis
: public AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis> {
friend AnalysisInfoMixin<OptimizationRemarkEmitterAnalysis>;
static AnalysisKey Key;
public:
/// Provide the result typedef for this analysis pass.
typedef OptimizationRemarkEmitter Result;
/// Run the analysis pass over a function and produce BFI.
Result run(Function &F, FunctionAnalysisManager &AM);
};
}
#endif // LLVM_ANALYSIS_OPTIMIZATIONREMARKEMITTER_H