| //===- 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/IR/Instructions.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| using namespace llvm; |
| |
| INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob", |
| "Machine Branch Probability Analysis", false, true) |
| INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "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 |
| |
| char MachineBranchProbabilityInfo::ID = 0; |
| |
| MachineBranchProbabilityInfo::MachineBranchProbabilityInfo() |
| : ImmutablePass(ID) { |
| PassRegistry &Registry = *PassRegistry::getPassRegistry(); |
| initializeMachineBranchProbabilityInfoPass(Registry); |
| } |
| |
| void MachineBranchProbabilityInfo::anchor() {} |
| |
| 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; |
| } |