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92 lines
3.2 KiB
C++
92 lines
3.2 KiB
C++
//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This analysis uses probability info stored in Machine Basic Blocks.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
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"Machine Branch Probability Analysis", false, true)
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INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob",
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"Machine Branch Probability Analysis", false, true)
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cl::opt<unsigned>
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StaticLikelyProb("static-likely-prob",
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cl::desc("branch probability threshold in percentage"
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"to be considered very likely"),
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cl::init(80), cl::Hidden);
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cl::opt<unsigned> ProfileLikelyProb(
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"profile-likely-prob",
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cl::desc("branch probability threshold in percentage to be considered"
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" very likely when profile is available"),
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cl::init(51), cl::Hidden);
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char MachineBranchProbabilityInfo::ID = 0;
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void MachineBranchProbabilityInfo::anchor() {}
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BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
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const MachineBasicBlock *Src,
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MachineBasicBlock::const_succ_iterator Dst) const {
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return Src->getSuccProbability(Dst);
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}
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BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
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const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
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// This is a linear search. Try to use the const_succ_iterator version when
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// possible.
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return getEdgeProbability(Src, find(Src->successors(), Dst));
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}
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bool MachineBranchProbabilityInfo::isEdgeHot(
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const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
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BranchProbability HotProb(StaticLikelyProb, 100);
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return getEdgeProbability(Src, Dst) > HotProb;
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}
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MachineBasicBlock *
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MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
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auto MaxProb = BranchProbability::getZero();
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MachineBasicBlock *MaxSucc = nullptr;
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for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
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E = MBB->succ_end(); I != E; ++I) {
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auto Prob = getEdgeProbability(MBB, I);
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if (Prob > MaxProb) {
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MaxProb = Prob;
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MaxSucc = *I;
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}
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}
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BranchProbability HotProb(StaticLikelyProb, 100);
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if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
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return MaxSucc;
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return nullptr;
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}
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raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
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raw_ostream &OS, const MachineBasicBlock *Src,
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const MachineBasicBlock *Dst) const {
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const BranchProbability Prob = getEdgeProbability(Src, Dst);
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OS << "edge " << printMBBReference(*Src) << " -> " << printMBBReference(*Dst)
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<< " probability is " << Prob
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<< (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
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return OS;
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}
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