llvm/llvm/include/llvm/Transforms/IPO/SampleProfileProbe.h

//===- Transforms/IPO/SampleProfileProbe.h ----------*- 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
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This file provides the interface for the pseudo probe implementation for
/// AutoFDO.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H
#define LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H

#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PassInstrumentation.h"
#include "llvm/ProfileData/SampleProf.h"
#include <unordered_map>

namespace llvm {
class BasicBlock;
class Function;
class Instruction;
class Loop;
class PassInstrumentationCallbacks;
class TargetMachine;

class Module;

usingnamespacesampleprof;
BlockIdMap;
InstructionIdMap;
// Map from tuples of Probe id and inline stack hash code to distribution
// factors.
ProbeFactorMap;
FuncProbeFactorMap;


// A pseudo probe verifier that can be run after each IR passes to detect the
// violation of updating probe factors. In principle, the sum of distribution
// factor for a probe should be identical before and after a pass. For a
// function pass, the factor sum for a probe would be typically 100%.
class PseudoProbeVerifier { … };

/// Sample profile pseudo prober.
///
/// Insert pseudo probes for block sampling and value sampling.
class SampleProfileProber { … };

class SampleProfileProbePass : public PassInfoMixin<SampleProfileProbePass> { … };

// Pseudo probe distribution factor updater.
// Sample profile annotation can happen in both LTO prelink and postlink. The
// postlink-time re-annotation can degrade profile quality because of prelink
// code duplication transformation, such as loop unrolling, jump threading,
// indirect call promotion etc. As such, samples corresponding to a source
// location may be aggregated multiple times in postlink. With a concept of
// distribution factor for pseudo probes, samples can be distributed among
// duplicated probes reasonable based on the assumption that optimizations
// duplicating code well-maintain the branch frequency information (BFI). This
// pass updates distribution factors for each pseudo probe at the end of the
// prelink pipeline, to reflect an estimated portion of the real execution
// count.
class PseudoProbeUpdatePass : public PassInfoMixin<PseudoProbeUpdatePass> { … };

} // end namespace llvm
#endif // LLVM_TRANSFORMS_IPO_SAMPLEPROFILEPROBE_H