Coverage Report

Created: 2019-02-21 13:17

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/BranchProbabilityInfo.h
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//===- BranchProbabilityInfo.h - Branch Probability Analysis ----*- C++ -*-===//
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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 pass is used to evaluate branch probabilties.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_BRANCHPROBABILITYINFO_H
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#define LLVM_ANALYSIS_BRANCHPROBABILITYINFO_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/BranchProbability.h"
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#include "llvm/Support/Casting.h"
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#include <algorithm>
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#include <cassert>
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#include <cstdint>
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#include <utility>
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namespace llvm {
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class Function;
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class LoopInfo;
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class raw_ostream;
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class TargetLibraryInfo;
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class Value;
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/// Analysis providing branch probability information.
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///
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/// This is a function analysis which provides information on the relative
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/// probabilities of each "edge" in the function's CFG where such an edge is
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/// defined by a pair (PredBlock and an index in the successors). The
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/// probability of an edge from one block is always relative to the
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/// probabilities of other edges from the block. The probabilites of all edges
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/// from a block sum to exactly one (100%).
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/// We use a pair (PredBlock and an index in the successors) to uniquely
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/// identify an edge, since we can have multiple edges from Src to Dst.
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/// As an example, we can have a switch which jumps to Dst with value 0 and
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/// value 10.
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class BranchProbabilityInfo {
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public:
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6.02M
  BranchProbabilityInfo() = default;
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  BranchProbabilityInfo(const Function &F, const LoopInfo &LI,
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                        const TargetLibraryInfo *TLI = nullptr) {
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    calculate(F, LI, TLI);
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  }
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  BranchProbabilityInfo(BranchProbabilityInfo &&Arg)
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      : Probs(std::move(Arg.Probs)), LastF(Arg.LastF),
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        PostDominatedByUnreachable(std::move(Arg.PostDominatedByUnreachable)),
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        PostDominatedByColdCall(std::move(Arg.PostDominatedByColdCall)) {}
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  BranchProbabilityInfo(const BranchProbabilityInfo &) = delete;
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  BranchProbabilityInfo &operator=(const BranchProbabilityInfo &) = delete;
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  BranchProbabilityInfo &operator=(BranchProbabilityInfo &&RHS) {
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0
    releaseMemory();
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    Probs = std::move(RHS.Probs);
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    PostDominatedByColdCall = std::move(RHS.PostDominatedByColdCall);
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    PostDominatedByUnreachable = std::move(RHS.PostDominatedByUnreachable);
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    return *this;
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  }
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  void releaseMemory();
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  void print(raw_ostream &OS) const;
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  /// Get an edge's probability, relative to other out-edges of the Src.
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  ///
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  /// This routine provides access to the fractional probability between zero
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  /// (0%) and one (100%) of this edge executing, relative to other edges
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  /// leaving the 'Src' block. The returned probability is never zero, and can
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  /// only be one if the source block has only one successor.
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  BranchProbability getEdgeProbability(const BasicBlock *Src,
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                                       unsigned IndexInSuccessors) const;
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  /// Get the probability of going from Src to Dst.
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  ///
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  /// It returns the sum of all probabilities for edges from Src to Dst.
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  BranchProbability getEdgeProbability(const BasicBlock *Src,
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                                       const BasicBlock *Dst) const;
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  BranchProbability getEdgeProbability(const BasicBlock *Src,
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                                       succ_const_iterator Dst) const;
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  /// Test if an edge is hot relative to other out-edges of the Src.
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  ///
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  /// Check whether this edge out of the source block is 'hot'. We define hot
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  /// as having a relative probability >= 80%.
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  bool isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const;
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  /// Retrieve the hot successor of a block if one exists.
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  ///
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  /// Given a basic block, look through its successors and if one exists for
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  /// which \see isEdgeHot would return true, return that successor block.
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  const BasicBlock *getHotSucc(const BasicBlock *BB) const;
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  /// Print an edge's probability.
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  ///
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  /// Retrieves an edge's probability similarly to \see getEdgeProbability, but
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  /// then prints that probability to the provided stream. That stream is then
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  /// returned.
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  raw_ostream &printEdgeProbability(raw_ostream &OS, const BasicBlock *Src,
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                                    const BasicBlock *Dst) const;
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  /// Set the raw edge probability for the given edge.
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  ///
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  /// This allows a pass to explicitly set the edge probability for an edge. It
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  /// can be used when updating the CFG to update and preserve the branch
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  /// probability information. Read the implementation of how these edge
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  /// probabilities are calculated carefully before using!
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  void setEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors,
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                          BranchProbability Prob);
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  static BranchProbability getBranchProbStackProtector(bool IsLikely) {
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    static const BranchProbability LikelyProb((1u << 20) - 1, 1u << 20);
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    return IsLikely ? 
LikelyProb2.82k
:
LikelyProb.getCompl()2.82k
;
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  }
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  void calculate(const Function &F, const LoopInfo &LI,
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                 const TargetLibraryInfo *TLI = nullptr);
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  /// Forget analysis results for the given basic block.
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  void eraseBlock(const BasicBlock *BB);
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  // Use to track SCCs for handling irreducible loops.
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  using SccMap = DenseMap<const BasicBlock *, int>;
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  using SccHeaderMap = DenseMap<const BasicBlock *, bool>;
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  using SccHeaderMaps = std::vector<SccHeaderMap>;
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  struct SccInfo {
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    SccMap SccNums;
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    SccHeaderMaps SccHeaders;
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  };
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private:
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  // We need to store CallbackVH's in order to correctly handle basic block
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  // removal.
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  class BasicBlockCallbackVH final : public CallbackVH {
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    BranchProbabilityInfo *BPI;
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    void deleted() override {
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      assert(BPI != nullptr);
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      BPI->eraseBlock(cast<BasicBlock>(getValPtr()));
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      BPI->Handles.erase(*this);
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    }
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  public:
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    BasicBlockCallbackVH(const Value *V, BranchProbabilityInfo *BPI = nullptr)
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        : CallbackVH(const_cast<Value *>(V)), BPI(BPI) {}
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  };
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  DenseSet<BasicBlockCallbackVH, DenseMapInfo<Value*>> Handles;
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  // Since we allow duplicate edges from one basic block to another, we use
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  // a pair (PredBlock and an index in the successors) to specify an edge.
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  using Edge = std::pair<const BasicBlock *, unsigned>;
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  // Default weight value. Used when we don't have information about the edge.
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  // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
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  // the successors have a weight yet. But it doesn't make sense when providing
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  // weight to an edge that may have siblings with non-zero weights. This can
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  // be handled various ways, but it's probably fine for an edge with unknown
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  // weight to just "inherit" the non-zero weight of an adjacent successor.
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  static const uint32_t DEFAULT_WEIGHT = 16;
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  DenseMap<Edge, BranchProbability> Probs;
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  /// Track the last function we run over for printing.
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  const Function *LastF;
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  /// Track the set of blocks directly succeeded by a returning block.
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  SmallPtrSet<const BasicBlock *, 16> PostDominatedByUnreachable;
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  /// Track the set of blocks that always lead to a cold call.
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  SmallPtrSet<const BasicBlock *, 16> PostDominatedByColdCall;
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  void updatePostDominatedByUnreachable(const BasicBlock *BB);
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  void updatePostDominatedByColdCall(const BasicBlock *BB);
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  bool calcUnreachableHeuristics(const BasicBlock *BB);
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  bool calcMetadataWeights(const BasicBlock *BB);
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  bool calcColdCallHeuristics(const BasicBlock *BB);
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  bool calcPointerHeuristics(const BasicBlock *BB);
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  bool calcLoopBranchHeuristics(const BasicBlock *BB, const LoopInfo &LI,
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                                SccInfo &SccI);
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  bool calcZeroHeuristics(const BasicBlock *BB, const TargetLibraryInfo *TLI);
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  bool calcFloatingPointHeuristics(const BasicBlock *BB);
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  bool calcInvokeHeuristics(const BasicBlock *BB);
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};
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/// Analysis pass which computes \c BranchProbabilityInfo.
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class BranchProbabilityAnalysis
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    : public AnalysisInfoMixin<BranchProbabilityAnalysis> {
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  friend AnalysisInfoMixin<BranchProbabilityAnalysis>;
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  static AnalysisKey Key;
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public:
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  /// Provide the result type for this analysis pass.
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  using Result = BranchProbabilityInfo;
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  /// Run the analysis pass over a function and produce BPI.
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  BranchProbabilityInfo run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Printer pass for the \c BranchProbabilityAnalysis results.
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class BranchProbabilityPrinterPass
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    : public PassInfoMixin<BranchProbabilityPrinterPass> {
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  raw_ostream &OS;
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public:
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  explicit BranchProbabilityPrinterPass(raw_ostream &OS) : OS(OS) {}
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  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Legacy analysis pass which computes \c BranchProbabilityInfo.
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class BranchProbabilityInfoWrapperPass : public FunctionPass {
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  BranchProbabilityInfo BPI;
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public:
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  static char ID;
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  BranchProbabilityInfoWrapperPass() : FunctionPass(ID) {
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    initializeBranchProbabilityInfoWrapperPassPass(
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        *PassRegistry::getPassRegistry());
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  }
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  BranchProbabilityInfo &getBPI() { return BPI; }
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  const BranchProbabilityInfo &getBPI() const { return BPI; }
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  void getAnalysisUsage(AnalysisUsage &AU) const override;
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  bool runOnFunction(Function &F) override;
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  void releaseMemory() override;
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  void print(raw_ostream &OS, const Module *M = nullptr) const override;
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};
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} // end namespace llvm
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#endif // LLVM_ANALYSIS_BRANCHPROBABILITYINFO_H