| 1 | //===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This analysis uses probability info stored in Machine Basic Blocks. |
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| 10 | // |
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| 11 | //===----------------------------------------------------------------------===// |
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| 12 | |
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| 13 | #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" |
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| 14 | #include "llvm/CodeGen/MachineBasicBlock.h" |
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| 15 | #include "llvm/InitializePasses.h" |
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| 16 | #include "llvm/Support/CommandLine.h" |
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| 17 | #include "llvm/Support/raw_ostream.h" |
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| 18 | |
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| 19 | using namespace llvm; |
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| 20 | |
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| 21 | INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob" , |
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| 22 | "Machine Branch Probability Analysis" , false, true) |
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| 23 | INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob" , |
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| 24 | "Machine Branch Probability Analysis" , false, true) |
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| 25 | |
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| 26 | namespace llvm { |
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| 27 | cl::opt<unsigned> |
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| 28 | StaticLikelyProb("static-likely-prob" , |
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| 29 | cl::desc("branch probability threshold in percentage" |
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| 30 | "to be considered very likely" ), |
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| 31 | cl::init(Val: 80), cl::Hidden); |
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| 32 | |
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| 33 | cl::opt<unsigned> ProfileLikelyProb( |
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| 34 | "profile-likely-prob" , |
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| 35 | cl::desc("branch probability threshold in percentage to be considered" |
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| 36 | " very likely when profile is available" ), |
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| 37 | cl::init(Val: 51), cl::Hidden); |
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| 38 | } // namespace llvm |
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| 39 | |
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| 40 | char MachineBranchProbabilityInfo::ID = 0; |
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| 41 | |
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| 42 | MachineBranchProbabilityInfo::MachineBranchProbabilityInfo() |
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| 43 | : ImmutablePass(ID) { |
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| 44 | PassRegistry &Registry = *PassRegistry::getPassRegistry(); |
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| 45 | initializeMachineBranchProbabilityInfoPass(Registry); |
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| 46 | } |
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| 47 | |
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| 48 | void MachineBranchProbabilityInfo::anchor() {} |
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| 49 | |
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| 50 | BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( |
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| 51 | const MachineBasicBlock *Src, |
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| 52 | MachineBasicBlock::const_succ_iterator Dst) const { |
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| 53 | return Src->getSuccProbability(Succ: Dst); |
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| 54 | } |
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| 55 | |
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| 56 | BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( |
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| 57 | const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { |
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| 58 | // This is a linear search. Try to use the const_succ_iterator version when |
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| 59 | // possible. |
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| 60 | return getEdgeProbability(Src, Dst: find(Range: Src->successors(), Val: Dst)); |
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| 61 | } |
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| 62 | |
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| 63 | bool MachineBranchProbabilityInfo::isEdgeHot( |
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| 64 | const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const { |
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| 65 | BranchProbability HotProb(StaticLikelyProb, 100); |
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| 66 | return getEdgeProbability(Src, Dst) > HotProb; |
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| 67 | } |
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| 68 | |
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| 69 | raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability( |
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| 70 | raw_ostream &OS, const MachineBasicBlock *Src, |
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| 71 | const MachineBasicBlock *Dst) const { |
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| 72 | |
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| 73 | const BranchProbability Prob = getEdgeProbability(Src, Dst); |
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| 74 | OS << "edge " << printMBBReference(MBB: *Src) << " -> " << printMBBReference(MBB: *Dst) |
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| 75 | << " probability is " << Prob |
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| 76 | << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n" ); |
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| 77 | |
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| 78 | return OS; |
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| 79 | } |
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| 80 | |
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