llvm/llvm/include/llvm/Analysis/LazyBranchProbabilityInfo.h

//===- LazyBranchProbabilityInfo.h - Lazy Branch Probability ----*- 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
//
//===----------------------------------------------------------------------===//
//
// This is an alternative analysis pass to BranchProbabilityInfoWrapperPass.
// The difference is that with this pass the branch probabilities are not
// computed when the analysis pass is executed but rather when the BPI results
// is explicitly requested by the analysis client.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H
#define LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H

#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Pass.h"

namespace llvm {
class Function;
class LoopInfo;
class TargetLibraryInfo;

/// This is an alternative analysis pass to
/// BranchProbabilityInfoWrapperPass.  The difference is that with this pass the
/// branch probabilities are not computed when the analysis pass is executed but
/// rather when the BPI results is explicitly requested by the analysis client.
///
/// There are some additional requirements for any client pass that wants to use
/// the analysis:
///
/// 1. The pass needs to initialize dependent passes with:
///
///   INITIALIZE_PASS_DEPENDENCY(LazyBPIPass)
///
/// 2. Similarly, getAnalysisUsage should call:
///
///   LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU)
///
/// 3. The computed BPI should be requested with
///    getAnalysis<LazyBranchProbabilityInfoPass>().getBPI() before LoopInfo
///    could be invalidated for example by changing the CFG.
///
/// Note that it is expected that we wouldn't need this functionality for the
/// new PM since with the new PM, analyses are executed on demand.
class LazyBranchProbabilityInfoPass : public FunctionPass { … };

/// Helper for client passes to initialize dependent passes for LBPI.
void initializeLazyBPIPassPass(PassRegistry &Registry);

/// Simple trait class that provides a mapping between BPI passes and the
/// corresponding BPInfo.
template <typename PassT> struct BPIPassTrait { … };

template <> struct BPIPassTrait<LazyBranchProbabilityInfoPass> { … };
} // namespace llvm
#endif