1263508Sdim//=- MachineBranchProbabilityInfo.h - Branch Probability Analysis -*- C++ -*-=// 2224133Sdim// 3224133Sdim// The LLVM Compiler Infrastructure 4224133Sdim// 5224133Sdim// This file is distributed under the University of Illinois Open Source 6224133Sdim// License. See LICENSE.TXT for details. 7224133Sdim// 8224133Sdim//===----------------------------------------------------------------------===// 9224133Sdim// 10224133Sdim// This pass is used to evaluate branch probabilties on machine basic blocks. 11224133Sdim// 12224133Sdim//===----------------------------------------------------------------------===// 13224133Sdim 14224133Sdim#ifndef LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H 15224133Sdim#define LLVM_CODEGEN_MACHINEBRANCHPROBABILITYINFO_H 16224133Sdim 17249423Sdim#include "llvm/CodeGen/MachineBasicBlock.h" 18224133Sdim#include "llvm/Pass.h" 19224133Sdim#include "llvm/Support/BranchProbability.h" 20224133Sdim#include <climits> 21224133Sdim 22224133Sdimnamespace llvm { 23224133Sdim 24224133Sdimclass MachineBranchProbabilityInfo : public ImmutablePass { 25234353Sdim virtual void anchor(); 26224133Sdim 27224133Sdim // Default weight value. Used when we don't have information about the edge. 28224133Sdim // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of 29224133Sdim // the successors have a weight yet. But it doesn't make sense when providing 30224133Sdim // weight to an edge that may have siblings with non-zero weights. This can 31224133Sdim // be handled various ways, but it's probably fine for an edge with unknown 32224133Sdim // weight to just "inherit" the non-zero weight of an adjacent successor. 33224133Sdim static const uint32_t DEFAULT_WEIGHT = 16; 34224133Sdim 35224133Sdimpublic: 36224133Sdim static char ID; 37224133Sdim 38224133Sdim MachineBranchProbabilityInfo() : ImmutablePass(ID) { 39224133Sdim PassRegistry &Registry = *PassRegistry::getPassRegistry(); 40224133Sdim initializeMachineBranchProbabilityInfoPass(Registry); 41224133Sdim } 42224133Sdim 43224133Sdim void getAnalysisUsage(AnalysisUsage &AU) const { 44224133Sdim AU.setPreservesAll(); 45224133Sdim } 46224133Sdim 47224133Sdim // Return edge weight. If we don't have any informations about it - return 48224133Sdim // DEFAULT_WEIGHT. 49234353Sdim uint32_t getEdgeWeight(const MachineBasicBlock *Src, 50234353Sdim const MachineBasicBlock *Dst) const; 51224133Sdim 52243830Sdim // Same thing, but using a const_succ_iterator from Src. This is faster when 53243830Sdim // the iterator is already available. 54243830Sdim uint32_t getEdgeWeight(const MachineBasicBlock *Src, 55243830Sdim MachineBasicBlock::const_succ_iterator Dst) const; 56243830Sdim 57234353Sdim // Get sum of the block successors' weights, potentially scaling them to fit 58234353Sdim // within 32-bits. If scaling is required, sets Scale based on the necessary 59234353Sdim // adjustment. Any edge weights used with the sum should be divided by Scale. 60234353Sdim uint32_t getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const; 61234353Sdim 62224133Sdim // A 'Hot' edge is an edge which probability is >= 80%. 63224133Sdim bool isEdgeHot(MachineBasicBlock *Src, MachineBasicBlock *Dst) const; 64224133Sdim 65224133Sdim // Return a hot successor for the block BB or null if there isn't one. 66234353Sdim // NB: This routine's complexity is linear on the number of successors. 67224133Sdim MachineBasicBlock *getHotSucc(MachineBasicBlock *MBB) const; 68224133Sdim 69224133Sdim // Return a probability as a fraction between 0 (0% probability) and 70224133Sdim // 1 (100% probability), however the value is never equal to 0, and can be 1 71224133Sdim // only iff SRC block has only one successor. 72234353Sdim // NB: This routine's complexity is linear on the number of successors of 73234353Sdim // Src. Querying sequentially for each successor's probability is a quadratic 74234353Sdim // query pattern. 75224133Sdim BranchProbability getEdgeProbability(MachineBasicBlock *Src, 76224133Sdim MachineBasicBlock *Dst) const; 77224133Sdim 78224133Sdim // Print value between 0 (0% probability) and 1 (100% probability), 79224133Sdim // however the value is never equal to 0, and can be 1 only iff SRC block 80224133Sdim // has only one successor. 81224133Sdim raw_ostream &printEdgeProbability(raw_ostream &OS, MachineBasicBlock *Src, 82224133Sdim MachineBasicBlock *Dst) const; 83224133Sdim}; 84224133Sdim 85224133Sdim} 86224133Sdim 87224133Sdim 88224133Sdim#endif 89