84 lines
2.8 KiB
C++
84 lines
2.8 KiB
C++
//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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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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,
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std::find(Src->succ_begin(), Src->succ_end(), Dst));
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}
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bool
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MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src,
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const MachineBasicBlock *Dst) const {
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// Hot probability is at least 4/5 = 80%
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static BranchProbability HotProb(4, 5);
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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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static BranchProbability HotProb(4, 5);
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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 MBB#" << Src->getNumber() << " -> MBB#" << Dst->getNumber()
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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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