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//===- LazyBlockFrequencyInfo.h - Lazy Block Frequency Analysis -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 results is explicitly
// requested by the analysis client.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
#define LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Pass.h"
namespace llvm {
class AnalysisUsage;
class BranchProbabilityInfo;
class Function;
class LoopInfo;
/// \brief 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 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(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 {
/// 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.
class LazyBlockFrequencyInfo {
public:
LazyBlockFrequencyInfo()
: Calculated(false), F(nullptr), BPI(nullptr), LI(nullptr) {}
/// Set up the per-function input.
void setAnalysis(const Function *F, const BranchProbabilityInfo *BPI,
const LoopInfo *LI) {
this->F = F;
this->BPI = BPI;
this->LI = LI;
}
/// Retrieve the BFI with the block frequencies computed.
BlockFrequencyInfo &getCalculated() {
if (!Calculated) {
assert(F && BPI && LI && "call setAnalysis");
BFI.calculate(*F, *BPI, *LI);
Calculated = true;
}
return BFI;
}
const BlockFrequencyInfo &getCalculated() const {
return const_cast<LazyBlockFrequencyInfo *>(this)->getCalculated();
}
void releaseMemory() {
BFI.releaseMemory();
Calculated = false;
setAnalysis(nullptr, nullptr, nullptr);
}
private:
BlockFrequencyInfo BFI;
bool Calculated;
const Function *F;
const BranchProbabilityInfo *BPI;
const LoopInfo *LI;
};
LazyBlockFrequencyInfo LBFI;
public:
static char ID;
LazyBlockFrequencyInfoPass();
/// \brief Compute and return the block frequencies.
BlockFrequencyInfo &getBFI() { return LBFI.getCalculated(); }
/// \brief 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;
};
/// \brief Helper for client passes to initialize dependent passes for LBFI.
void initializeLazyBFIPassPass(PassRegistry &Registry);
}
#endif
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