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//===- LazyBlockFrequencyInfo.h - Lazy Block Frequency Analysis -*- 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 BlockFrequencyInfoWrapperPass. The
// difference is that with this pass the block frequencies are not computed when
// the analysis pass is executed but rather when the BFI result is explicitly
// requested by the analysis client.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
#define LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/LazyBranchProbabilityInfo.h"
#include "llvm/Pass.h"
namespace llvm {
class AnalysisUsage;
class Function;
class LoopInfo;
/// Wraps a BFI to allow lazy computation of the block frequencies.
///
/// A pass that only conditionally uses BFI can uncondtionally require the
/// analysis without paying for the overhead if BFI doesn't end up being used.
template <typename FunctionT, typename BranchProbabilityInfoPassT,
typename LoopInfoT, typename BlockFrequencyInfoT>
class LazyBlockFrequencyInfo {
public:
LazyBlockFrequencyInfo() = default;
/// Set up the per-function input.
void setAnalysis(const FunctionT *F, BranchProbabilityInfoPassT *BPIPass,
const LoopInfoT *LI) {
this->F = F;
this->BPIPass = BPIPass;
this->LI = LI;
}
/// Retrieve the BFI with the block frequencies computed.
BlockFrequencyInfoT &getCalculated() {
if (!Calculated) {
assert(F && BPIPass && LI && "call setAnalysis");
BFI.calculate(
*F, BPIPassTrait<BranchProbabilityInfoPassT>::getBPI(BPIPass), *LI);
Calculated = true;
}
return BFI;
}
const BlockFrequencyInfoT &getCalculated() const {
return const_cast<LazyBlockFrequencyInfo *>(this)->getCalculated();
}
void releaseMemory() {
BFI.releaseMemory();
Calculated = false;
setAnalysis(nullptr, nullptr, nullptr);
}
private:
BlockFrequencyInfoT BFI;
bool Calculated = false;
const FunctionT *F = nullptr;
BranchProbabilityInfoPassT *BPIPass = nullptr;
const LoopInfoT *LI = nullptr;
};
/// This is an alternative analysis pass to
/// BlockFrequencyInfoWrapperPass. The difference is that with this pass the
/// block frequencies are not computed when the analysis pass is executed but
/// rather when the BFI result 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(LazyBFIPass)
///
/// 2. Similarly, getAnalysisUsage should call:
///
/// LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU)
///
/// 3. The computed BFI should be requested with
/// getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() before either LoopInfo
/// or BPI 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 LazyBlockFrequencyInfoPass : public FunctionPass {
private:
LazyBlockFrequencyInfo<Function, LazyBranchProbabilityInfoPass, LoopInfo,
BlockFrequencyInfo>
LBFI;
public:
static char ID;
LazyBlockFrequencyInfoPass();
/// Compute and return the block frequencies.
BlockFrequencyInfo &getBFI() { return LBFI.getCalculated(); }
/// Compute and return the block frequencies.
const BlockFrequencyInfo &getBFI() const { return LBFI.getCalculated(); }
void getAnalysisUsage(AnalysisUsage &AU) const override;
/// Helper for client passes to set up the analysis usage on behalf of this
/// pass.
static void getLazyBFIAnalysisUsage(AnalysisUsage &AU);
bool runOnFunction(Function &F) override;
void releaseMemory() override;
void print(raw_ostream &OS, const Module *M) const override;
};
/// Helper for client passes to initialize dependent passes for LBFI.
void initializeLazyBFIPassPass(PassRegistry &Registry);
}
#endif
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