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14edd314af
to bring it under direct test instead of merely indirectly testing it in the BlockFrequencyInfo pass. The next step is to start adding tests for the various heuristics employed, and to start fixing those heuristics once they're under test. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142778 91177308-0d34-0410-b5e6-96231b3b80d8
87 lines
3.1 KiB
C++
87 lines
3.1 KiB
C++
//===--- BranchProbabilityInfo.h - Branch Probability Analysis --*- C++ -*-===//
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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 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/InitializePasses.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/Support/BranchProbability.h"
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namespace llvm {
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class raw_ostream;
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class BranchProbabilityInfo : public FunctionPass {
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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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typedef std::pair<const BasicBlock *, const BasicBlock *> Edge;
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DenseMap<Edge, uint32_t> Weights;
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/// \brief Track the last function we run over for printing.
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Function *LastF;
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// Get sum of the block successors' weights.
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uint32_t getSumForBlock(const BasicBlock *BB) const;
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public:
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static char ID;
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BranchProbabilityInfo() : FunctionPass(ID) {
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initializeBranchProbabilityInfoPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const;
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bool runOnFunction(Function &F);
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void print(raw_ostream &OS, const Module *M = 0) const;
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// Returned value is between 1 and UINT32_MAX. Look at
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// BranchProbabilityInfo.cpp for details.
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uint32_t getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const;
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// Look at BranchProbabilityInfo.cpp for details. Use it with caution!
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void setEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst,
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uint32_t Weight);
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// A 'Hot' edge is an edge which probability is >= 80%.
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bool isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const;
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// Return a hot successor for the block BB or null if there isn't one.
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BasicBlock *getHotSucc(BasicBlock *BB) const;
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// Return a probability as a fraction between 0 (0% probability) and
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// 1 (100% probability), however the value is never equal to 0, and can be 1
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// only iff SRC block has only one successor.
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BranchProbability getEdgeProbability(const BasicBlock *Src,
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const BasicBlock *Dst) const;
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// Print value between 0 (0% probability) and 1 (100% probability),
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// however the value is never equal to 0, and can be 1 only iff SRC block
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// has only one successor.
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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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};
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}
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#endif
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