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//=- MachineBranchProbabilityInfo.h - Branch Probability 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 pass is used to evaluate branch probabilties on machine basic blocks.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
#define LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachinePassManager.h"
#include "llvm/Pass.h"
#include "llvm/Support/BranchProbability.h"
namespace llvm {
class MachineBranchProbabilityInfo {
// Default weight value. Used when we don't have information about the edge.
// TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
// the successors have a weight yet. But it doesn't make sense when providing
// weight to an edge that may have siblings with non-zero weights. This can
// be handled various ways, but it's probably fine for an edge with unknown
// weight to just "inherit" the non-zero weight of an adjacent successor.
static const uint32_t DEFAULT_WEIGHT = 16;
public:
bool invalidate(MachineFunction &, const PreservedAnalyses &PA,
MachineFunctionAnalysisManager::Invalidator &);
// Return edge probability.
BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;
// Same as above, but using a const_succ_iterator from Src. This is faster
// when the iterator is already available.
BranchProbability
getEdgeProbability(const MachineBasicBlock *Src,
MachineBasicBlock::const_succ_iterator Dst) const;
// A 'Hot' edge is an edge which probability is >= 80%.
bool isEdgeHot(const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;
// Print value between 0 (0% probability) and 1 (100% probability),
// however the value is never equal to 0, and can be 1 only iff SRC block
// has only one successor.
raw_ostream &printEdgeProbability(raw_ostream &OS,
const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;
};
class MachineBranchProbabilityAnalysis
: public AnalysisInfoMixin<MachineBranchProbabilityAnalysis> {
friend AnalysisInfoMixin<MachineBranchProbabilityAnalysis>;
static AnalysisKey Key;
public:
using Result = MachineBranchProbabilityInfo;
Result run(MachineFunction &, MachineFunctionAnalysisManager &);
};
class MachineBranchProbabilityPrinterPass
: public PassInfoMixin<MachineBranchProbabilityPrinterPass> {
raw_ostream &OS;
public:
MachineBranchProbabilityPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(MachineFunction &MF,
MachineFunctionAnalysisManager &MFAM);
};
class MachineBranchProbabilityInfoWrapperPass : public ImmutablePass {
virtual void anchor();
MachineBranchProbabilityInfo MBPI;
public:
static char ID;
MachineBranchProbabilityInfoWrapperPass();
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
}
MachineBranchProbabilityInfo &getMBPI() { return MBPI; }
const MachineBranchProbabilityInfo &getMBPI() const { return MBPI; }
};
}
#endif
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