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//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
//
// 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 analysis uses probability info stored in Machine Basic Blocks.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfoWrapperPass,
"machine-branch-prob",
"Machine Branch Probability Analysis", false, true)
INITIALIZE_PASS_END(MachineBranchProbabilityInfoWrapperPass,
"machine-branch-prob",
"Machine Branch Probability Analysis", false, true)
namespace llvm {
cl::opt<unsigned>
StaticLikelyProb("static-likely-prob",
cl::desc("branch probability threshold in percentage"
" to be considered very likely"),
cl::init(80), cl::Hidden);
cl::opt<unsigned> ProfileLikelyProb(
"profile-likely-prob",
cl::desc("branch probability threshold in percentage to be considered"
" very likely when profile is available"),
cl::init(51), cl::Hidden);
} // namespace llvm
MachineBranchProbabilityAnalysis::Result
MachineBranchProbabilityAnalysis::run(MachineFunction &,
MachineFunctionAnalysisManager &) {
return MachineBranchProbabilityInfo();
}
PreservedAnalyses
MachineBranchProbabilityPrinterPass::run(MachineFunction &MF,
MachineFunctionAnalysisManager &MFAM) {
OS << "Printing analysis 'Machine Branch Probability Analysis' for machine "
"function '"
<< MF.getName() << "':\n";
auto &MBPI = MFAM.getResult<MachineBranchProbabilityAnalysis>(MF);
for (const MachineBasicBlock &MBB : MF) {
for (const MachineBasicBlock *Succ : MBB.successors())
MBPI.printEdgeProbability(OS << " ", &MBB, Succ);
}
return PreservedAnalyses::all();
}
char MachineBranchProbabilityInfoWrapperPass::ID = 0;
MachineBranchProbabilityInfoWrapperPass::
MachineBranchProbabilityInfoWrapperPass()
: ImmutablePass(ID) {
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeMachineBranchProbabilityInfoWrapperPassPass(Registry);
}
void MachineBranchProbabilityInfoWrapperPass::anchor() {}
AnalysisKey MachineBranchProbabilityAnalysis::Key;
bool MachineBranchProbabilityInfo::invalidate(
MachineFunction &, const PreservedAnalyses &PA,
MachineFunctionAnalysisManager::Invalidator &) {
auto PAC = PA.getChecker<MachineBranchProbabilityAnalysis>();
return !PAC.preservedWhenStateless();
}
BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
const MachineBasicBlock *Src,
MachineBasicBlock::const_succ_iterator Dst) const {
return Src->getSuccProbability(Dst);
}
BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
// This is a linear search. Try to use the const_succ_iterator version when
// possible.
return getEdgeProbability(Src, find(Src->successors(), Dst));
}
bool MachineBranchProbabilityInfo::isEdgeHot(
const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
BranchProbability HotProb(StaticLikelyProb, 100);
return getEdgeProbability(Src, Dst) > HotProb;
}
raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
raw_ostream &OS, const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const {
const BranchProbability Prob = getEdgeProbability(Src, Dst);
OS << "edge " << printMBBReference(*Src) << " -> " << printMBBReference(*Dst)
<< " probability is " << Prob
<< (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
return OS;
}
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