1 //===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This analysis uses probability info stored in Machine Basic Blocks. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" 14 #include "llvm/CodeGen/MachineBasicBlock.h" 15 #include "llvm/InitializePasses.h" 16 #include "llvm/Support/CommandLine.h" 17 #include "llvm/Support/raw_ostream.h" 18 19 using namespace llvm; 20 21 INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfoWrapperPass, 22 "machine-branch-prob", 23 "Machine Branch Probability Analysis", false, true) 24 INITIALIZE_PASS_END(MachineBranchProbabilityInfoWrapperPass, 25 "machine-branch-prob", 26 "Machine Branch Probability Analysis", false, true) 27 28 namespace llvm { 29 cl::opt<unsigned> 30 StaticLikelyProb("static-likely-prob", 31 cl::desc("branch probability threshold in percentage" 32 "to be considered very likely"), 33 cl::init(80), cl::Hidden); 34 35 cl::opt<unsigned> ProfileLikelyProb( 36 "profile-likely-prob", 37 cl::desc("branch probability threshold in percentage to be considered" 38 " very likely when profile is available"), 39 cl::init(51), cl::Hidden); 40 } // namespace llvm 41 42 MachineBranchProbabilityAnalysis::Result 43 MachineBranchProbabilityAnalysis::run(MachineFunction &, 44 MachineFunctionAnalysisManager &) { 45 return MachineBranchProbabilityInfo(); 46 } 47 48 PreservedAnalyses 49 MachineBranchProbabilityPrinterPass::run(MachineFunction &MF, 50 MachineFunctionAnalysisManager &MFAM) { 51 OS << "Printing analysis 'Machine Branch Probability Analysis' for machine " 52 "function '" 53 << MF.getName() << "':\n"; 54 auto &MBPI = MFAM.getResult<MachineBranchProbabilityAnalysis>(MF); 55 for (const MachineBasicBlock &MBB : MF) { 56 for (const MachineBasicBlock *Succ : MBB.successors()) 57 MBPI.printEdgeProbability(OS << " ", &MBB, Succ); 58 } 59 return PreservedAnalyses::all(); 60 } 61 62 char MachineBranchProbabilityInfoWrapperPass::ID = 0; 63 64 MachineBranchProbabilityInfoWrapperPass:: 65 MachineBranchProbabilityInfoWrapperPass() 66 : ImmutablePass(ID) { 67 PassRegistry &Registry = *PassRegistry::getPassRegistry(); 68 initializeMachineBranchProbabilityInfoWrapperPassPass(Registry); 69 } 70 71 void MachineBranchProbabilityInfoWrapperPass::anchor() {} 72 73 AnalysisKey MachineBranchProbabilityAnalysis::Key; 74 75 bool MachineBranchProbabilityInfo::invalidate( 76 MachineFunction &, const PreservedAnalyses &PA, 77 MachineFunctionAnalysisManager::Invalidator &) { 78 auto PAC = PA.getChecker<MachineBranchProbabilityAnalysis>(); 79 return !PAC.preservedWhenStateless(); 80 } 81 82 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( 83 const MachineBasicBlock *Src, 84 MachineBasicBlock::const_succ_iterator Dst) const { 85 return Src->getSuccProbability(Dst); 86 } 87 88 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( 89 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { 90 // This is a linear search. Try to use the const_succ_iterator version when 91 // possible. 92 return getEdgeProbability(Src, find(Src->successors(), Dst)); 93 } 94 95 bool MachineBranchProbabilityInfo::isEdgeHot( 96 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { 97 BranchProbability HotProb(StaticLikelyProb, 100); 98 return getEdgeProbability(Src, Dst) > HotProb; 99 } 100 101 raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability( 102 raw_ostream &OS, const MachineBasicBlock *Src, 103 const MachineBasicBlock *Dst) const { 104 105 const BranchProbability Prob = getEdgeProbability(Src, Dst); 106 OS << "edge " << printMBBReference(*Src) << " -> " << printMBBReference(*Dst) 107 << " probability is " << Prob 108 << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n"); 109 110 return OS; 111 } 112