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5155021519
(This is the second attempt to submit this patch. The first caused two assertion failures and was reverted. See https://llvm.org/bugs/show_bug.cgi?id=25687) The patch in http://reviews.llvm.org/D13745 is broken into four parts: 1. New interfaces without functional changes (http://reviews.llvm.org/D13908). 2. Use new interfaces in SelectionDAG, while in other passes treat probabilities as weights (http://reviews.llvm.org/D14361). 3. Use new interfaces in all other passes. 4. Remove old interfaces. This patch is 3+4 above. In this patch, MBB won't provide weight-based interfaces any more, which are totally replaced by probability-based ones. The interface addSuccessor() is redesigned so that the default probability is unknown. We allow unknown probabilities but don't allow using it together with known probabilities in successor list. That is to say, we either have a list of successors with all known probabilities, or all unknown probabilities. In the latter case, we assume each successor has 1/N probability where N is the number of successors. An assertion checks if the user is attempting to add a successor with the disallowed mixed use as stated above. This can help us catch many misuses. All uses of weight-based interfaces are now updated to use probability-based ones. Differential revision: http://reviews.llvm.org/D14973 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254377 91177308-0d34-0410-b5e6-96231b3b80d8
97 lines
3.3 KiB
C++
97 lines
3.3 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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uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
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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).getNumerator();
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}
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uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
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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 getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
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}
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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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