1 //===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This analysis uses probability info stored in Machine Basic Blocks.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
15 #include "llvm/CodeGen/MachineBasicBlock.h"
16 #include "llvm/IR/Instructions.h"
17 #include "llvm/Support/Debug.h"
18 #include "llvm/Support/raw_ostream.h"
22 INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
23 "Machine Branch Probability Analysis", false, true)
24 INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob",
25 "Machine Branch Probability Analysis", false, true)
27 char MachineBranchProbabilityInfo::ID = 0;
29 void MachineBranchProbabilityInfo::anchor() { }
31 uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
32 const MachineBasicBlock *Src,
33 MachineBasicBlock::const_succ_iterator Dst) const {
34 return Src->getSuccProbability(Dst).getNumerator();
37 uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
38 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
39 // This is a linear search. Try to use the const_succ_iterator version when
41 return getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
44 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
45 const MachineBasicBlock *Src,
46 MachineBasicBlock::const_succ_iterator Dst) const {
47 return Src->getSuccProbability(Dst);
50 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
51 const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
52 // This is a linear search. Try to use the const_succ_iterator version when
54 return getEdgeProbability(Src,
55 std::find(Src->succ_begin(), Src->succ_end(), Dst));
59 MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src,
60 const MachineBasicBlock *Dst) const {
61 // Hot probability is at least 4/5 = 80%
62 static BranchProbability HotProb(4, 5);
63 return getEdgeProbability(Src, Dst) > HotProb;
67 MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
68 auto MaxProb = BranchProbability::getZero();
69 MachineBasicBlock *MaxSucc = nullptr;
70 for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
71 E = MBB->succ_end(); I != E; ++I) {
72 auto Prob = getEdgeProbability(MBB, I);
79 static BranchProbability HotProb(4, 5);
80 if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
86 raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
87 raw_ostream &OS, const MachineBasicBlock *Src,
88 const MachineBasicBlock *Dst) const {
90 const BranchProbability Prob = getEdgeProbability(Src, Dst);
91 OS << "edge MBB#" << Src->getNumber() << " -> MBB#" << Dst->getNumber()
92 << " probability is " << Prob
93 << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");