686 lines
23 KiB
C++
686 lines
23 KiB
C++
//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===//
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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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// Loops should be simplified before this analysis.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/BranchProbabilityInfo.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Metadata.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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#define DEBUG_TYPE "branch-prob"
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INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
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"Branch Probability Analysis", false, true)
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INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
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INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
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"Branch Probability Analysis", false, true)
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char BranchProbabilityInfoWrapperPass::ID = 0;
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// Weights are for internal use only. They are used by heuristics to help to
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// estimate edges' probability. Example:
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//
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// Using "Loop Branch Heuristics" we predict weights of edges for the
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// block BB2.
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// ...
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// |
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// V
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// BB1<-+
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// | |
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// | | (Weight = 124)
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// V |
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// BB2--+
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// |
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// | (Weight = 4)
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// V
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// BB3
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//
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// Probability of the edge BB2->BB1 = 124 / (124 + 4) = 0.96875
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// Probability of the edge BB2->BB3 = 4 / (124 + 4) = 0.03125
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static const uint32_t LBH_TAKEN_WEIGHT = 124;
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static const uint32_t LBH_NONTAKEN_WEIGHT = 4;
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/// \brief Unreachable-terminating branch taken weight.
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///
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/// This is the weight for a branch being taken to a block that terminates
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/// (eventually) in unreachable. These are predicted as unlikely as possible.
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static const uint32_t UR_TAKEN_WEIGHT = 1;
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/// \brief Unreachable-terminating branch not-taken weight.
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///
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/// This is the weight for a branch not being taken toward a block that
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/// terminates (eventually) in unreachable. Such a branch is essentially never
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/// taken. Set the weight to an absurdly high value so that nested loops don't
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/// easily subsume it.
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static const uint32_t UR_NONTAKEN_WEIGHT = 1024*1024 - 1;
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/// \brief Weight for a branch taken going into a cold block.
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///
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/// This is the weight for a branch taken toward a block marked
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/// cold. A block is marked cold if it's postdominated by a
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/// block containing a call to a cold function. Cold functions
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/// are those marked with attribute 'cold'.
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static const uint32_t CC_TAKEN_WEIGHT = 4;
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/// \brief Weight for a branch not-taken into a cold block.
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///
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/// This is the weight for a branch not taken toward a block marked
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/// cold.
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static const uint32_t CC_NONTAKEN_WEIGHT = 64;
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static const uint32_t PH_TAKEN_WEIGHT = 20;
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static const uint32_t PH_NONTAKEN_WEIGHT = 12;
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static const uint32_t ZH_TAKEN_WEIGHT = 20;
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static const uint32_t ZH_NONTAKEN_WEIGHT = 12;
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static const uint32_t FPH_TAKEN_WEIGHT = 20;
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static const uint32_t FPH_NONTAKEN_WEIGHT = 12;
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/// \brief Invoke-terminating normal branch taken weight
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///
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/// This is the weight for branching to the normal destination of an invoke
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/// instruction. We expect this to happen most of the time. Set the weight to an
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/// absurdly high value so that nested loops subsume it.
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static const uint32_t IH_TAKEN_WEIGHT = 1024 * 1024 - 1;
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/// \brief Invoke-terminating normal branch not-taken weight.
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///
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/// This is the weight for branching to the unwind destination of an invoke
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/// instruction. This is essentially never taken.
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static const uint32_t IH_NONTAKEN_WEIGHT = 1;
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/// \brief Calculate edge weights for successors lead to unreachable.
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///
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/// Predict that a successor which leads necessarily to an
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/// unreachable-terminated block as extremely unlikely.
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bool BranchProbabilityInfo::calcUnreachableHeuristics(BasicBlock *BB) {
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TerminatorInst *TI = BB->getTerminator();
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if (TI->getNumSuccessors() == 0) {
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if (isa<UnreachableInst>(TI))
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PostDominatedByUnreachable.insert(BB);
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return false;
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}
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SmallVector<unsigned, 4> UnreachableEdges;
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SmallVector<unsigned, 4> ReachableEdges;
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for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
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if (PostDominatedByUnreachable.count(*I))
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UnreachableEdges.push_back(I.getSuccessorIndex());
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else
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ReachableEdges.push_back(I.getSuccessorIndex());
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}
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// If all successors are in the set of blocks post-dominated by unreachable,
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// this block is too.
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if (UnreachableEdges.size() == TI->getNumSuccessors())
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PostDominatedByUnreachable.insert(BB);
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// Skip probabilities if this block has a single successor or if all were
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// reachable.
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if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
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return false;
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// If the terminator is an InvokeInst, check only the normal destination block
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// as the unwind edge of InvokeInst is also very unlikely taken.
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if (auto *II = dyn_cast<InvokeInst>(TI))
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if (PostDominatedByUnreachable.count(II->getNormalDest())) {
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PostDominatedByUnreachable.insert(BB);
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// Return false here so that edge weights for InvokeInst could be decided
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// in calcInvokeHeuristics().
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return false;
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}
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if (ReachableEdges.empty()) {
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BranchProbability Prob(1, UnreachableEdges.size());
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for (unsigned SuccIdx : UnreachableEdges)
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setEdgeProbability(BB, SuccIdx, Prob);
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return true;
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}
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BranchProbability UnreachableProb(UR_TAKEN_WEIGHT,
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(UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
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UnreachableEdges.size());
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BranchProbability ReachableProb(UR_NONTAKEN_WEIGHT,
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(UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
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ReachableEdges.size());
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for (unsigned SuccIdx : UnreachableEdges)
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setEdgeProbability(BB, SuccIdx, UnreachableProb);
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for (unsigned SuccIdx : ReachableEdges)
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setEdgeProbability(BB, SuccIdx, ReachableProb);
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return true;
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}
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// Propagate existing explicit probabilities from either profile data or
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// 'expect' intrinsic processing.
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bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) {
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TerminatorInst *TI = BB->getTerminator();
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if (TI->getNumSuccessors() == 1)
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return false;
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if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
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return false;
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MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
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if (!WeightsNode)
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return false;
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// Check that the number of successors is manageable.
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assert(TI->getNumSuccessors() < UINT32_MAX && "Too many successors");
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// Ensure there are weights for all of the successors. Note that the first
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// operand to the metadata node is a name, not a weight.
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if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1)
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return false;
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// Build up the final weights that will be used in a temporary buffer.
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// Compute the sum of all weights to later decide whether they need to
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// be scaled to fit in 32 bits.
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uint64_t WeightSum = 0;
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SmallVector<uint32_t, 2> Weights;
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Weights.reserve(TI->getNumSuccessors());
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for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
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ConstantInt *Weight =
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mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(i));
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if (!Weight)
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return false;
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assert(Weight->getValue().getActiveBits() <= 32 &&
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"Too many bits for uint32_t");
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Weights.push_back(Weight->getZExtValue());
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WeightSum += Weights.back();
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}
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assert(Weights.size() == TI->getNumSuccessors() && "Checked above");
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// If the sum of weights does not fit in 32 bits, scale every weight down
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// accordingly.
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uint64_t ScalingFactor =
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(WeightSum > UINT32_MAX) ? WeightSum / UINT32_MAX + 1 : 1;
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WeightSum = 0;
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
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Weights[i] /= ScalingFactor;
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WeightSum += Weights[i];
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}
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if (WeightSum == 0) {
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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setEdgeProbability(BB, i, {1, e});
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} else {
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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setEdgeProbability(BB, i, {Weights[i], static_cast<uint32_t>(WeightSum)});
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}
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assert(WeightSum <= UINT32_MAX &&
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"Expected weights to scale down to 32 bits");
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return true;
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}
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/// \brief Calculate edge weights for edges leading to cold blocks.
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///
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/// A cold block is one post-dominated by a block with a call to a
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/// cold function. Those edges are unlikely to be taken, so we give
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/// them relatively low weight.
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///
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/// Return true if we could compute the weights for cold edges.
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/// Return false, otherwise.
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bool BranchProbabilityInfo::calcColdCallHeuristics(BasicBlock *BB) {
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TerminatorInst *TI = BB->getTerminator();
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if (TI->getNumSuccessors() == 0)
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return false;
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// Determine which successors are post-dominated by a cold block.
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SmallVector<unsigned, 4> ColdEdges;
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SmallVector<unsigned, 4> NormalEdges;
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for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I)
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if (PostDominatedByColdCall.count(*I))
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ColdEdges.push_back(I.getSuccessorIndex());
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else
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NormalEdges.push_back(I.getSuccessorIndex());
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// If all successors are in the set of blocks post-dominated by cold calls,
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// this block is in the set post-dominated by cold calls.
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if (ColdEdges.size() == TI->getNumSuccessors())
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PostDominatedByColdCall.insert(BB);
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else {
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// Otherwise, if the block itself contains a cold function, add it to the
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// set of blocks postdominated by a cold call.
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assert(!PostDominatedByColdCall.count(BB));
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
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if (CallInst *CI = dyn_cast<CallInst>(I))
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if (CI->hasFnAttr(Attribute::Cold)) {
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PostDominatedByColdCall.insert(BB);
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break;
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}
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}
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// Skip probabilities if this block has a single successor.
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if (TI->getNumSuccessors() == 1 || ColdEdges.empty())
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return false;
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if (NormalEdges.empty()) {
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BranchProbability Prob(1, ColdEdges.size());
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for (unsigned SuccIdx : ColdEdges)
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setEdgeProbability(BB, SuccIdx, Prob);
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return true;
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}
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BranchProbability ColdProb(CC_TAKEN_WEIGHT,
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(CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
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ColdEdges.size());
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BranchProbability NormalProb(CC_NONTAKEN_WEIGHT,
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(CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
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NormalEdges.size());
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for (unsigned SuccIdx : ColdEdges)
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setEdgeProbability(BB, SuccIdx, ColdProb);
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for (unsigned SuccIdx : NormalEdges)
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setEdgeProbability(BB, SuccIdx, NormalProb);
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return true;
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}
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// Calculate Edge Weights using "Pointer Heuristics". Predict a comparsion
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// between two pointer or pointer and NULL will fail.
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bool BranchProbabilityInfo::calcPointerHeuristics(BasicBlock *BB) {
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BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
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if (!BI || !BI->isConditional())
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return false;
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Value *Cond = BI->getCondition();
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ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
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if (!CI || !CI->isEquality())
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return false;
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Value *LHS = CI->getOperand(0);
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if (!LHS->getType()->isPointerTy())
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return false;
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assert(CI->getOperand(1)->getType()->isPointerTy());
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// p != 0 -> isProb = true
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// p == 0 -> isProb = false
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// p != q -> isProb = true
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// p == q -> isProb = false;
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unsigned TakenIdx = 0, NonTakenIdx = 1;
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bool isProb = CI->getPredicate() == ICmpInst::ICMP_NE;
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if (!isProb)
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std::swap(TakenIdx, NonTakenIdx);
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BranchProbability TakenProb(PH_TAKEN_WEIGHT,
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PH_TAKEN_WEIGHT + PH_NONTAKEN_WEIGHT);
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setEdgeProbability(BB, TakenIdx, TakenProb);
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setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
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return true;
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}
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// Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
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// as taken, exiting edges as not-taken.
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bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB,
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const LoopInfo &LI) {
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Loop *L = LI.getLoopFor(BB);
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if (!L)
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return false;
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SmallVector<unsigned, 8> BackEdges;
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SmallVector<unsigned, 8> ExitingEdges;
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SmallVector<unsigned, 8> InEdges; // Edges from header to the loop.
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for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
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if (!L->contains(*I))
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ExitingEdges.push_back(I.getSuccessorIndex());
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else if (L->getHeader() == *I)
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BackEdges.push_back(I.getSuccessorIndex());
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else
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InEdges.push_back(I.getSuccessorIndex());
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}
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if (BackEdges.empty() && ExitingEdges.empty())
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return false;
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// Collect the sum of probabilities of back-edges/in-edges/exiting-edges, and
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// normalize them so that they sum up to one.
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SmallVector<BranchProbability, 4> Probs(3, BranchProbability::getZero());
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unsigned Denom = (BackEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
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(InEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
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(ExitingEdges.empty() ? 0 : LBH_NONTAKEN_WEIGHT);
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if (!BackEdges.empty())
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Probs[0] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
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if (!InEdges.empty())
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Probs[1] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
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if (!ExitingEdges.empty())
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Probs[2] = BranchProbability(LBH_NONTAKEN_WEIGHT, Denom);
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if (uint32_t numBackEdges = BackEdges.size()) {
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auto Prob = Probs[0] / numBackEdges;
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for (unsigned SuccIdx : BackEdges)
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setEdgeProbability(BB, SuccIdx, Prob);
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}
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if (uint32_t numInEdges = InEdges.size()) {
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auto Prob = Probs[1] / numInEdges;
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for (unsigned SuccIdx : InEdges)
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setEdgeProbability(BB, SuccIdx, Prob);
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}
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if (uint32_t numExitingEdges = ExitingEdges.size()) {
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auto Prob = Probs[2] / numExitingEdges;
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for (unsigned SuccIdx : ExitingEdges)
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setEdgeProbability(BB, SuccIdx, Prob);
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}
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return true;
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}
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bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) {
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BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
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if (!BI || !BI->isConditional())
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return false;
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Value *Cond = BI->getCondition();
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ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
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if (!CI)
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return false;
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Value *RHS = CI->getOperand(1);
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ConstantInt *CV = dyn_cast<ConstantInt>(RHS);
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if (!CV)
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return false;
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// If the LHS is the result of AND'ing a value with a single bit bitmask,
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// we don't have information about probabilities.
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if (Instruction *LHS = dyn_cast<Instruction>(CI->getOperand(0)))
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if (LHS->getOpcode() == Instruction::And)
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if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(LHS->getOperand(1)))
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if (AndRHS->getUniqueInteger().isPowerOf2())
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return false;
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bool isProb;
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if (CV->isZero()) {
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switch (CI->getPredicate()) {
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case CmpInst::ICMP_EQ:
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// X == 0 -> Unlikely
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isProb = false;
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break;
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case CmpInst::ICMP_NE:
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// X != 0 -> Likely
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isProb = true;
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break;
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case CmpInst::ICMP_SLT:
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// X < 0 -> Unlikely
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isProb = false;
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break;
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case CmpInst::ICMP_SGT:
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// X > 0 -> Likely
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isProb = true;
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break;
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default:
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return false;
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}
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} else if (CV->isOne() && CI->getPredicate() == CmpInst::ICMP_SLT) {
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// InstCombine canonicalizes X <= 0 into X < 1.
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// X <= 0 -> Unlikely
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isProb = false;
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} else if (CV->isAllOnesValue()) {
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switch (CI->getPredicate()) {
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case CmpInst::ICMP_EQ:
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// X == -1 -> Unlikely
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isProb = false;
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break;
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case CmpInst::ICMP_NE:
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// X != -1 -> Likely
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isProb = true;
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break;
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case CmpInst::ICMP_SGT:
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// InstCombine canonicalizes X >= 0 into X > -1.
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// X >= 0 -> Likely
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isProb = true;
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break;
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default:
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return false;
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}
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} else {
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return false;
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}
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unsigned TakenIdx = 0, NonTakenIdx = 1;
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if (!isProb)
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std::swap(TakenIdx, NonTakenIdx);
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BranchProbability TakenProb(ZH_TAKEN_WEIGHT,
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ZH_TAKEN_WEIGHT + ZH_NONTAKEN_WEIGHT);
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setEdgeProbability(BB, TakenIdx, TakenProb);
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setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
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return true;
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}
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bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) {
|
|
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
|
|
if (!BI || !BI->isConditional())
|
|
return false;
|
|
|
|
Value *Cond = BI->getCondition();
|
|
FCmpInst *FCmp = dyn_cast<FCmpInst>(Cond);
|
|
if (!FCmp)
|
|
return false;
|
|
|
|
bool isProb;
|
|
if (FCmp->isEquality()) {
|
|
// f1 == f2 -> Unlikely
|
|
// f1 != f2 -> Likely
|
|
isProb = !FCmp->isTrueWhenEqual();
|
|
} else if (FCmp->getPredicate() == FCmpInst::FCMP_ORD) {
|
|
// !isnan -> Likely
|
|
isProb = true;
|
|
} else if (FCmp->getPredicate() == FCmpInst::FCMP_UNO) {
|
|
// isnan -> Unlikely
|
|
isProb = false;
|
|
} else {
|
|
return false;
|
|
}
|
|
|
|
unsigned TakenIdx = 0, NonTakenIdx = 1;
|
|
|
|
if (!isProb)
|
|
std::swap(TakenIdx, NonTakenIdx);
|
|
|
|
BranchProbability TakenProb(FPH_TAKEN_WEIGHT,
|
|
FPH_TAKEN_WEIGHT + FPH_NONTAKEN_WEIGHT);
|
|
setEdgeProbability(BB, TakenIdx, TakenProb);
|
|
setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
|
|
return true;
|
|
}
|
|
|
|
bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
|
|
InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator());
|
|
if (!II)
|
|
return false;
|
|
|
|
BranchProbability TakenProb(IH_TAKEN_WEIGHT,
|
|
IH_TAKEN_WEIGHT + IH_NONTAKEN_WEIGHT);
|
|
setEdgeProbability(BB, 0 /*Index for Normal*/, TakenProb);
|
|
setEdgeProbability(BB, 1 /*Index for Unwind*/, TakenProb.getCompl());
|
|
return true;
|
|
}
|
|
|
|
void BranchProbabilityInfo::releaseMemory() {
|
|
Probs.clear();
|
|
}
|
|
|
|
void BranchProbabilityInfo::print(raw_ostream &OS) const {
|
|
OS << "---- Branch Probabilities ----\n";
|
|
// We print the probabilities from the last function the analysis ran over,
|
|
// or the function it is currently running over.
|
|
assert(LastF && "Cannot print prior to running over a function");
|
|
for (const auto &BI : *LastF) {
|
|
for (succ_const_iterator SI = succ_begin(&BI), SE = succ_end(&BI); SI != SE;
|
|
++SI) {
|
|
printEdgeProbability(OS << " ", &BI, *SI);
|
|
}
|
|
}
|
|
}
|
|
|
|
bool BranchProbabilityInfo::
|
|
isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const {
|
|
// Hot probability is at least 4/5 = 80%
|
|
// FIXME: Compare against a static "hot" BranchProbability.
|
|
return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
|
|
}
|
|
|
|
BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const {
|
|
auto MaxProb = BranchProbability::getZero();
|
|
BasicBlock *MaxSucc = nullptr;
|
|
|
|
for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
|
|
BasicBlock *Succ = *I;
|
|
auto Prob = getEdgeProbability(BB, Succ);
|
|
if (Prob > MaxProb) {
|
|
MaxProb = Prob;
|
|
MaxSucc = Succ;
|
|
}
|
|
}
|
|
|
|
// Hot probability is at least 4/5 = 80%
|
|
if (MaxProb > BranchProbability(4, 5))
|
|
return MaxSucc;
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Get the raw edge probability for the edge. If can't find it, return a
|
|
/// default probability 1/N where N is the number of successors. Here an edge is
|
|
/// specified using PredBlock and an
|
|
/// index to the successors.
|
|
BranchProbability
|
|
BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
|
|
unsigned IndexInSuccessors) const {
|
|
auto I = Probs.find(std::make_pair(Src, IndexInSuccessors));
|
|
|
|
if (I != Probs.end())
|
|
return I->second;
|
|
|
|
return {1,
|
|
static_cast<uint32_t>(std::distance(succ_begin(Src), succ_end(Src)))};
|
|
}
|
|
|
|
BranchProbability
|
|
BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
|
|
succ_const_iterator Dst) const {
|
|
return getEdgeProbability(Src, Dst.getSuccessorIndex());
|
|
}
|
|
|
|
/// Get the raw edge probability calculated for the block pair. This returns the
|
|
/// sum of all raw edge probabilities from Src to Dst.
|
|
BranchProbability
|
|
BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
|
|
const BasicBlock *Dst) const {
|
|
auto Prob = BranchProbability::getZero();
|
|
bool FoundProb = false;
|
|
for (succ_const_iterator I = succ_begin(Src), E = succ_end(Src); I != E; ++I)
|
|
if (*I == Dst) {
|
|
auto MapI = Probs.find(std::make_pair(Src, I.getSuccessorIndex()));
|
|
if (MapI != Probs.end()) {
|
|
FoundProb = true;
|
|
Prob += MapI->second;
|
|
}
|
|
}
|
|
uint32_t succ_num = std::distance(succ_begin(Src), succ_end(Src));
|
|
return FoundProb ? Prob : BranchProbability(1, succ_num);
|
|
}
|
|
|
|
/// Set the edge probability for a given edge specified by PredBlock and an
|
|
/// index to the successors.
|
|
void BranchProbabilityInfo::setEdgeProbability(const BasicBlock *Src,
|
|
unsigned IndexInSuccessors,
|
|
BranchProbability Prob) {
|
|
Probs[std::make_pair(Src, IndexInSuccessors)] = Prob;
|
|
DEBUG(dbgs() << "set edge " << Src->getName() << " -> " << IndexInSuccessors
|
|
<< " successor probability to " << Prob << "\n");
|
|
}
|
|
|
|
raw_ostream &
|
|
BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
|
|
const BasicBlock *Src,
|
|
const BasicBlock *Dst) const {
|
|
|
|
const BranchProbability Prob = getEdgeProbability(Src, Dst);
|
|
OS << "edge " << Src->getName() << " -> " << Dst->getName()
|
|
<< " probability is " << Prob
|
|
<< (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
|
|
|
|
return OS;
|
|
}
|
|
|
|
void BranchProbabilityInfo::calculate(Function &F, const LoopInfo& LI) {
|
|
DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
|
|
<< " ----\n\n");
|
|
LastF = &F; // Store the last function we ran on for printing.
|
|
assert(PostDominatedByUnreachable.empty());
|
|
assert(PostDominatedByColdCall.empty());
|
|
|
|
// Walk the basic blocks in post-order so that we can build up state about
|
|
// the successors of a block iteratively.
|
|
for (auto BB : post_order(&F.getEntryBlock())) {
|
|
DEBUG(dbgs() << "Computing probabilities for " << BB->getName() << "\n");
|
|
if (calcUnreachableHeuristics(BB))
|
|
continue;
|
|
if (calcMetadataWeights(BB))
|
|
continue;
|
|
if (calcColdCallHeuristics(BB))
|
|
continue;
|
|
if (calcLoopBranchHeuristics(BB, LI))
|
|
continue;
|
|
if (calcPointerHeuristics(BB))
|
|
continue;
|
|
if (calcZeroHeuristics(BB))
|
|
continue;
|
|
if (calcFloatingPointHeuristics(BB))
|
|
continue;
|
|
calcInvokeHeuristics(BB);
|
|
}
|
|
|
|
PostDominatedByUnreachable.clear();
|
|
PostDominatedByColdCall.clear();
|
|
}
|
|
|
|
void BranchProbabilityInfoWrapperPass::getAnalysisUsage(
|
|
AnalysisUsage &AU) const {
|
|
AU.addRequired<LoopInfoWrapperPass>();
|
|
AU.setPreservesAll();
|
|
}
|
|
|
|
bool BranchProbabilityInfoWrapperPass::runOnFunction(Function &F) {
|
|
const LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
|
|
BPI.calculate(F, LI);
|
|
return false;
|
|
}
|
|
|
|
void BranchProbabilityInfoWrapperPass::releaseMemory() { BPI.releaseMemory(); }
|
|
|
|
void BranchProbabilityInfoWrapperPass::print(raw_ostream &OS,
|
|
const Module *) const {
|
|
BPI.print(OS);
|
|
}
|