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(MachineBranchProbabilityInfo, "machine-branch-prob", 22 "Machine Branch Probability Analysis", false, true) 23 INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob", 24 "Machine Branch Probability Analysis", false, true) 25 26 namespace llvm { 27 cl::opt<unsigned> 28 StaticLikelyProb("static-likely-prob", 29 cl::desc("branch probability threshold in percentage" 30 "to be considered very likely"), 31 cl::init(80), cl::Hidden); 32 33 cl::opt<unsigned> ProfileLikelyProb( 34 "profile-likely-prob", 35 cl::desc("branch probability threshold in percentage to be considered" 36 " very likely when profile is available"), 37 cl::init(51), cl::Hidden); 38 } // namespace llvm 39 40 char MachineBranchProbabilityInfo::ID = 0; 41 42 MachineBranchProbabilityInfo::MachineBranchProbabilityInfo() 43 : ImmutablePass(ID) { 44 PassRegistry &Registry = *PassRegistry::getPassRegistry(); 45 initializeMachineBranchProbabilityInfoPass(Registry); 46 } 47 48 void MachineBranchProbabilityInfo::anchor() {} 49 50 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( 51 const MachineBasicBlock *Src, 52 MachineBasicBlock::const_succ_iterator Dst) const { 53 return Src->getSuccProbability(Dst); 54 } 55 56 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( 57 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { 58 // This is a linear search. Try to use the const_succ_iterator version when 59 // possible. 60 return getEdgeProbability(Src, find(Src->successors(), Dst)); 61 } 62 63 bool MachineBranchProbabilityInfo::isEdgeHot( 64 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { 65 BranchProbability HotProb(StaticLikelyProb, 100); 66 return getEdgeProbability(Src, Dst) > HotProb; 67 } 68 69 raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability( 70 raw_ostream &OS, const MachineBasicBlock *Src, 71 const MachineBasicBlock *Dst) const { 72 73 const BranchProbability Prob = getEdgeProbability(Src, Dst); 74 OS << "edge " << printMBBReference(*Src) << " -> " << printMBBReference(*Dst) 75 << " probability is " << Prob 76 << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n"); 77 78 return OS; 79 } 80