X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FBranchProbabilityInfo.cpp;h=15491f072cc8f08eaca447e8d07922fb8f9a0cb3;hb=5be77762a3aa434ee877b0a03b98b5c3a7571918;hp=c6f6fa77bc294bb472afc4004cc7ec51eee73cc6;hpb=b137f16936a3f3b5a3463eff6cd433e99ac37cb6;p=oota-llvm.git diff --git a/lib/Analysis/BranchProbabilityInfo.cpp b/lib/Analysis/BranchProbabilityInfo.cpp index c6f6fa77bc2..15491f072cc 100644 --- a/lib/Analysis/BranchProbabilityInfo.cpp +++ b/lib/Analysis/BranchProbabilityInfo.cpp @@ -1,4 +1,4 @@ -//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -*- C++ -*-===// +//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===// // // The LLVM Compiler Infrastructure // @@ -11,10 +11,16 @@ // //===----------------------------------------------------------------------===// -#include "llvm/Constants.h" -#include "llvm/Instructions.h" +#define DEBUG_TYPE "branch-prob" #include "llvm/Analysis/BranchProbabilityInfo.h" +#include "llvm/ADT/PostOrderIterator.h" #include "llvm/Analysis/LoopInfo.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Metadata.h" +#include "llvm/Support/CFG.h" #include "llvm/Support/Debug.h" using namespace llvm; @@ -27,158 +33,245 @@ INITIALIZE_PASS_END(BranchProbabilityInfo, "branch-prob", char BranchProbabilityInfo::ID = 0; -namespace { -// Please note that BranchProbabilityAnalysis is not a FunctionPass. -// It is created by BranchProbabilityInfo (which is a FunctionPass), which -// provides a clear interface. Thanks to that, all heuristics and other -// private methods are hidden in the .cpp file. -class BranchProbabilityAnalysis { - - typedef std::pair Edge; - - DenseMap *Weights; - - BranchProbabilityInfo *BP; - - LoopInfo *LI; - - - // Weights are for internal use only. They are used by heuristics to help to - // estimate edges' probability. Example: - // - // Using "Loop Branch Heuristics" we predict weights of edges for the - // block BB2. - // ... - // | - // V - // BB1<-+ - // | | - // | | (Weight = 124) - // V | - // BB2--+ - // | - // | (Weight = 4) - // V - // BB3 - // - // Probability of the edge BB2->BB1 = 124 / (124 + 4) = 0.96875 - // Probability of the edge BB2->BB3 = 4 / (124 + 4) = 0.03125 - - static const uint32_t LBH_TAKEN_WEIGHT = 124; - static const uint32_t LBH_NONTAKEN_WEIGHT = 4; - - static const uint32_t RH_TAKEN_WEIGHT = 24; - static const uint32_t RH_NONTAKEN_WEIGHT = 8; - - static const uint32_t PH_TAKEN_WEIGHT = 20; - static const uint32_t PH_NONTAKEN_WEIGHT = 12; +// Weights are for internal use only. They are used by heuristics to help to +// estimate edges' probability. Example: +// +// Using "Loop Branch Heuristics" we predict weights of edges for the +// block BB2. +// ... +// | +// V +// BB1<-+ +// | | +// | | (Weight = 124) +// V | +// BB2--+ +// | +// | (Weight = 4) +// V +// BB3 +// +// Probability of the edge BB2->BB1 = 124 / (124 + 4) = 0.96875 +// Probability of the edge BB2->BB3 = 4 / (124 + 4) = 0.03125 +static const uint32_t LBH_TAKEN_WEIGHT = 124; +static const uint32_t LBH_NONTAKEN_WEIGHT = 4; + +/// \brief Unreachable-terminating branch taken weight. +/// +/// This is the weight for a branch being taken to a block that terminates +/// (eventually) in unreachable. These are predicted as unlikely as possible. +static const uint32_t UR_TAKEN_WEIGHT = 1; + +/// \brief Unreachable-terminating branch not-taken weight. +/// +/// This is the weight for a branch not being taken toward a block that +/// terminates (eventually) in unreachable. Such a branch is essentially never +/// taken. Set the weight to an absurdly high value so that nested loops don't +/// easily subsume it. +static const uint32_t UR_NONTAKEN_WEIGHT = 1024*1024 - 1; + +/// \brief Weight for a branch taken going into a cold block. +/// +/// This is the weight for a branch taken toward a block marked +/// cold. A block is marked cold if it's postdominated by a +/// block containing a call to a cold function. Cold functions +/// are those marked with attribute 'cold'. +static const uint32_t CC_TAKEN_WEIGHT = 4; + +/// \brief Weight for a branch not-taken into a cold block. +/// +/// This is the weight for a branch not taken toward a block marked +/// cold. +static const uint32_t CC_NONTAKEN_WEIGHT = 64; + +static const uint32_t PH_TAKEN_WEIGHT = 20; +static const uint32_t PH_NONTAKEN_WEIGHT = 12; + +static const uint32_t ZH_TAKEN_WEIGHT = 20; +static const uint32_t ZH_NONTAKEN_WEIGHT = 12; + +static const uint32_t FPH_TAKEN_WEIGHT = 20; +static const uint32_t FPH_NONTAKEN_WEIGHT = 12; + +/// \brief Invoke-terminating normal branch taken weight +/// +/// This is the weight for branching to the normal destination of an invoke +/// instruction. We expect this to happen most of the time. Set the weight to an +/// absurdly high value so that nested loops subsume it. +static const uint32_t IH_TAKEN_WEIGHT = 1024 * 1024 - 1; + +/// \brief Invoke-terminating normal branch not-taken weight. +/// +/// This is the weight for branching to the unwind destination of an invoke +/// instruction. This is essentially never taken. +static const uint32_t IH_NONTAKEN_WEIGHT = 1; + +// Standard weight value. Used when none of the heuristics set weight for +// the edge. +static const uint32_t NORMAL_WEIGHT = 16; + +// Minimum weight of an edge. Please note, that weight is NEVER 0. +static const uint32_t MIN_WEIGHT = 1; + +static uint32_t getMaxWeightFor(BasicBlock *BB) { + return UINT32_MAX / BB->getTerminator()->getNumSuccessors(); +} - static const uint32_t ZH_TAKEN_WEIGHT = 20; - static const uint32_t ZH_NONTAKEN_WEIGHT = 12; - // Standard weight value. Used when none of the heuristics set weight for - // the edge. - static const uint32_t NORMAL_WEIGHT = 16; +/// \brief Calculate edge weights for successors lead to unreachable. +/// +/// Predict that a successor which leads necessarily to an +/// unreachable-terminated block as extremely unlikely. +bool BranchProbabilityInfo::calcUnreachableHeuristics(BasicBlock *BB) { + TerminatorInst *TI = BB->getTerminator(); + if (TI->getNumSuccessors() == 0) { + if (isa(TI)) + PostDominatedByUnreachable.insert(BB); + return false; + } - // Minimum weight of an edge. Please note, that weight is NEVER 0. - static const uint32_t MIN_WEIGHT = 1; + SmallVector UnreachableEdges; + SmallVector ReachableEdges; - // Return TRUE if BB leads directly to a Return Instruction. - static bool isReturningBlock(BasicBlock *BB) { - SmallPtrSet Visited; + for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) { + if (PostDominatedByUnreachable.count(*I)) + UnreachableEdges.push_back(I.getSuccessorIndex()); + else + ReachableEdges.push_back(I.getSuccessorIndex()); + } - while (true) { - TerminatorInst *TI = BB->getTerminator(); - if (isa(TI)) - return true; + // If all successors are in the set of blocks post-dominated by unreachable, + // this block is too. + if (UnreachableEdges.size() == TI->getNumSuccessors()) + PostDominatedByUnreachable.insert(BB); - if (TI->getNumSuccessors() > 1) - break; + // Skip probabilities if this block has a single successor or if all were + // reachable. + if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty()) + return false; - // It is unreachable block which we can consider as a return instruction. - if (TI->getNumSuccessors() == 0) - return true; + uint32_t UnreachableWeight = + std::max(UR_TAKEN_WEIGHT / (unsigned)UnreachableEdges.size(), MIN_WEIGHT); + for (SmallVectorImpl::iterator I = UnreachableEdges.begin(), + E = UnreachableEdges.end(); + I != E; ++I) + setEdgeWeight(BB, *I, UnreachableWeight); + + if (ReachableEdges.empty()) + return true; + uint32_t ReachableWeight = + std::max(UR_NONTAKEN_WEIGHT / (unsigned)ReachableEdges.size(), + NORMAL_WEIGHT); + for (SmallVectorImpl::iterator I = ReachableEdges.begin(), + E = ReachableEdges.end(); + I != E; ++I) + setEdgeWeight(BB, *I, ReachableWeight); - Visited.insert(BB); - BB = TI->getSuccessor(0); + return true; +} - // Stop if cycle is detected. - if (Visited.count(BB)) - return false; - } +// Propagate existing explicit probabilities from either profile data or +// 'expect' intrinsic processing. +bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) { + TerminatorInst *TI = BB->getTerminator(); + if (TI->getNumSuccessors() == 1) + return false; + if (!isa(TI) && !isa(TI)) + return false; + MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof); + if (!WeightsNode) return false; - } - uint32_t getMaxWeightFor(BasicBlock *BB) const { - return UINT32_MAX / BB->getTerminator()->getNumSuccessors(); - } + // Ensure there are weights for all of the successors. Note that the first + // operand to the metadata node is a name, not a weight. + if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1) + return false; -public: - BranchProbabilityAnalysis(DenseMap *W, - BranchProbabilityInfo *BP, LoopInfo *LI) - : Weights(W), BP(BP), LI(LI) { + // Build up the final weights that will be used in a temporary buffer, but + // don't add them until all weihts are present. Each weight value is clamped + // to [1, getMaxWeightFor(BB)]. + uint32_t WeightLimit = getMaxWeightFor(BB); + SmallVector Weights; + Weights.reserve(TI->getNumSuccessors()); + for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) { + ConstantInt *Weight = dyn_cast(WeightsNode->getOperand(i)); + if (!Weight) + return false; + Weights.push_back( + std::max(1, Weight->getLimitedValue(WeightLimit))); } + assert(Weights.size() == TI->getNumSuccessors() && "Checked above"); + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + setEdgeWeight(BB, i, Weights[i]); - // Return Heuristics - bool calcReturnHeuristics(BasicBlock *BB); - - // Pointer Heuristics - bool calcPointerHeuristics(BasicBlock *BB); - - // Loop Branch Heuristics - bool calcLoopBranchHeuristics(BasicBlock *BB); - - // Zero Heurestics - bool calcZeroHeuristics(BasicBlock *BB); - - bool runOnFunction(Function &F); -}; -} // end anonymous namespace + return true; +} -// Calculate Edge Weights using "Return Heuristics". Predict a successor which -// leads directly to Return Instruction will not be taken. -bool BranchProbabilityAnalysis::calcReturnHeuristics(BasicBlock *BB){ - if (BB->getTerminator()->getNumSuccessors() == 1) +/// \brief Calculate edge weights for edges leading to cold blocks. +/// +/// A cold block is one post-dominated by a block with a call to a +/// cold function. Those edges are unlikely to be taken, so we give +/// them relatively low weight. +/// +/// Return true if we could compute the weights for cold edges. +/// Return false, otherwise. +bool BranchProbabilityInfo::calcColdCallHeuristics(BasicBlock *BB) { + TerminatorInst *TI = BB->getTerminator(); + if (TI->getNumSuccessors() == 0) return false; - SmallPtrSet ReturningEdges; - SmallPtrSet StayEdges; - - for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) { - BasicBlock *Succ = *I; - if (isReturningBlock(Succ)) - ReturningEdges.insert(Succ); + // Determine which successors are post-dominated by a cold block. + SmallVector ColdEdges; + SmallVector NormalEdges; + for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) + if (PostDominatedByColdCall.count(*I)) + ColdEdges.push_back(I.getSuccessorIndex()); else - StayEdges.insert(Succ); + NormalEdges.push_back(I.getSuccessorIndex()); + + // If all successors are in the set of blocks post-dominated by cold calls, + // this block is in the set post-dominated by cold calls. + if (ColdEdges.size() == TI->getNumSuccessors()) + PostDominatedByColdCall.insert(BB); + else { + // Otherwise, if the block itself contains a cold function, add it to the + // set of blocks postdominated by a cold call. + assert(!PostDominatedByColdCall.count(BB)); + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) + if (CallInst *CI = dyn_cast(I)) + if (CI->hasFnAttr(Attribute::Cold)) { + PostDominatedByColdCall.insert(BB); + break; + } } - if (uint32_t numStayEdges = StayEdges.size()) { - uint32_t stayWeight = RH_TAKEN_WEIGHT / numStayEdges; - if (stayWeight < NORMAL_WEIGHT) - stayWeight = NORMAL_WEIGHT; + // Skip probabilities if this block has a single successor. + if (TI->getNumSuccessors() == 1 || ColdEdges.empty()) + return false; - for (SmallPtrSet::iterator I = StayEdges.begin(), - E = StayEdges.end(); I != E; ++I) - BP->setEdgeWeight(BB, *I, stayWeight); - } + uint32_t ColdWeight = + std::max(CC_TAKEN_WEIGHT / (unsigned) ColdEdges.size(), MIN_WEIGHT); + for (SmallVectorImpl::iterator I = ColdEdges.begin(), + E = ColdEdges.end(); + I != E; ++I) + setEdgeWeight(BB, *I, ColdWeight); + + if (NormalEdges.empty()) + return true; + uint32_t NormalWeight = std::max( + CC_NONTAKEN_WEIGHT / (unsigned) NormalEdges.size(), NORMAL_WEIGHT); + for (SmallVectorImpl::iterator I = NormalEdges.begin(), + E = NormalEdges.end(); + I != E; ++I) + setEdgeWeight(BB, *I, NormalWeight); - if (uint32_t numRetEdges = ReturningEdges.size()) { - uint32_t retWeight = RH_NONTAKEN_WEIGHT / numRetEdges; - if (retWeight < MIN_WEIGHT) - retWeight = MIN_WEIGHT; - for (SmallPtrSet::iterator I = ReturningEdges.begin(), - E = ReturningEdges.end(); I != E; ++I) { - BP->setEdgeWeight(BB, *I, retWeight); - } - } - - return ReturningEdges.size() > 0; + return true; } // Calculate Edge Weights using "Pointer Heuristics". Predict a comparsion // between two pointer or pointer and NULL will fail. -bool BranchProbabilityAnalysis::calcPointerHeuristics(BasicBlock *BB) { +bool BranchProbabilityInfo::calcPointerHeuristics(BasicBlock *BB) { BranchInst * BI = dyn_cast(BB->getTerminator()); if (!BI || !BI->isConditional()) return false; @@ -195,46 +288,38 @@ bool BranchProbabilityAnalysis::calcPointerHeuristics(BasicBlock *BB) { assert(CI->getOperand(1)->getType()->isPointerTy()); - BasicBlock *Taken = BI->getSuccessor(0); - BasicBlock *NonTaken = BI->getSuccessor(1); - // p != 0 -> isProb = true // p == 0 -> isProb = false // p != q -> isProb = true // p == q -> isProb = false; + unsigned TakenIdx = 0, NonTakenIdx = 1; bool isProb = CI->getPredicate() == ICmpInst::ICMP_NE; if (!isProb) - std::swap(Taken, NonTaken); + std::swap(TakenIdx, NonTakenIdx); - BP->setEdgeWeight(BB, Taken, PH_TAKEN_WEIGHT); - BP->setEdgeWeight(BB, NonTaken, PH_NONTAKEN_WEIGHT); + setEdgeWeight(BB, TakenIdx, PH_TAKEN_WEIGHT); + setEdgeWeight(BB, NonTakenIdx, PH_NONTAKEN_WEIGHT); return true; } // Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges // as taken, exiting edges as not-taken. -bool BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) { - uint32_t numSuccs = BB->getTerminator()->getNumSuccessors(); - +bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB) { Loop *L = LI->getLoopFor(BB); if (!L) return false; - SmallPtrSet BackEdges; - SmallPtrSet ExitingEdges; - SmallPtrSet InEdges; // Edges from header to the loop. - - bool isHeader = BB == L->getHeader(); + SmallVector BackEdges; + SmallVector ExitingEdges; + SmallVector InEdges; // Edges from header to the loop. for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) { - BasicBlock *Succ = *I; - Loop *SuccL = LI->getLoopFor(Succ); - if (SuccL != L) - ExitingEdges.insert(Succ); - else if (Succ == L->getHeader()) - BackEdges.insert(Succ); - else if (isHeader) - InEdges.insert(Succ); + if (!L->contains(*I)) + ExitingEdges.push_back(I.getSuccessorIndex()); + else if (L->getHeader() == *I) + BackEdges.push_back(I.getSuccessorIndex()); + else + InEdges.push_back(I.getSuccessorIndex()); } if (uint32_t numBackEdges = BackEdges.size()) { @@ -242,10 +327,9 @@ bool BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) { if (backWeight < NORMAL_WEIGHT) backWeight = NORMAL_WEIGHT; - for (SmallPtrSet::iterator EI = BackEdges.begin(), + for (SmallVectorImpl::iterator EI = BackEdges.begin(), EE = BackEdges.end(); EI != EE; ++EI) { - BasicBlock *Back = *EI; - BP->setEdgeWeight(BB, Back, backWeight); + setEdgeWeight(BB, *EI, backWeight); } } @@ -254,30 +338,27 @@ bool BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) { if (inWeight < NORMAL_WEIGHT) inWeight = NORMAL_WEIGHT; - for (SmallPtrSet::iterator EI = InEdges.begin(), + for (SmallVectorImpl::iterator EI = InEdges.begin(), EE = InEdges.end(); EI != EE; ++EI) { - BasicBlock *Back = *EI; - BP->setEdgeWeight(BB, Back, inWeight); + setEdgeWeight(BB, *EI, inWeight); } } - uint32_t numExitingEdges = ExitingEdges.size(); - if (uint32_t numNonExitingEdges = numSuccs - numExitingEdges) { - uint32_t exitWeight = LBH_NONTAKEN_WEIGHT / numNonExitingEdges; + if (uint32_t numExitingEdges = ExitingEdges.size()) { + uint32_t exitWeight = LBH_NONTAKEN_WEIGHT / numExitingEdges; if (exitWeight < MIN_WEIGHT) exitWeight = MIN_WEIGHT; - for (SmallPtrSet::iterator EI = ExitingEdges.begin(), + for (SmallVectorImpl::iterator EI = ExitingEdges.begin(), EE = ExitingEdges.end(); EI != EE; ++EI) { - BasicBlock *Exiting = *EI; - BP->setEdgeWeight(BB, Exiting, exitWeight); + setEdgeWeight(BB, *EI, exitWeight); } } return true; } -bool BranchProbabilityAnalysis::calcZeroHeuristics(BasicBlock *BB) { +bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) { BranchInst * BI = dyn_cast(BB->getTerminator()); if (!BI || !BI->isConditional()) return false; @@ -289,88 +370,174 @@ bool BranchProbabilityAnalysis::calcZeroHeuristics(BasicBlock *BB) { Value *RHS = CI->getOperand(1); ConstantInt *CV = dyn_cast(RHS); - if (!CV || !CV->isZero()) + if (!CV) return false; bool isProb; - switch (CI->getPredicate()) { - case CmpInst::ICMP_EQ: - // Equal to zero is not expected to be taken. + if (CV->isZero()) { + switch (CI->getPredicate()) { + case CmpInst::ICMP_EQ: + // X == 0 -> Unlikely + isProb = false; + break; + case CmpInst::ICMP_NE: + // X != 0 -> Likely + isProb = true; + break; + case CmpInst::ICMP_SLT: + // X < 0 -> Unlikely + isProb = false; + break; + case CmpInst::ICMP_SGT: + // X > 0 -> Likely + isProb = true; + break; + default: + return false; + } + } else if (CV->isOne() && CI->getPredicate() == CmpInst::ICMP_SLT) { + // InstCombine canonicalizes X <= 0 into X < 1. + // X <= 0 -> Unlikely isProb = false; - break; + } else if (CV->isAllOnesValue()) { + switch (CI->getPredicate()) { + case CmpInst::ICMP_EQ: + // X == -1 -> Unlikely + isProb = false; + break; + case CmpInst::ICMP_NE: + // X != -1 -> Likely + isProb = true; + break; + case CmpInst::ICMP_SGT: + // InstCombine canonicalizes X >= 0 into X > -1. + // X >= 0 -> Likely + isProb = true; + break; + default: + return false; + } + } else { + return false; + } - case CmpInst::ICMP_NE: - // Not equal to zero is expected. - isProb = true; - break; + unsigned TakenIdx = 0, NonTakenIdx = 1; - case CmpInst::ICMP_SLT: - // Less or equal to zero is not expected. - // X < 0 -> Unlikely - isProb = false; - break; + if (!isProb) + std::swap(TakenIdx, NonTakenIdx); - case CmpInst::ICMP_UGT: - case CmpInst::ICMP_SGT: - // Greater or equal to zero is expected. - // X > 0 -> Likely - isProb = true; - break; + setEdgeWeight(BB, TakenIdx, ZH_TAKEN_WEIGHT); + setEdgeWeight(BB, NonTakenIdx, ZH_NONTAKEN_WEIGHT); - default: + return true; +} + +bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) { + BranchInst *BI = dyn_cast(BB->getTerminator()); + if (!BI || !BI->isConditional()) + return false; + + Value *Cond = BI->getCondition(); + FCmpInst *FCmp = dyn_cast(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; - }; + } - BasicBlock *Taken = BI->getSuccessor(0); - BasicBlock *NonTaken = BI->getSuccessor(1); + unsigned TakenIdx = 0, NonTakenIdx = 1; if (!isProb) - std::swap(Taken, NonTaken); + std::swap(TakenIdx, NonTakenIdx); - BP->setEdgeWeight(BB, Taken, ZH_TAKEN_WEIGHT); - BP->setEdgeWeight(BB, NonTaken, ZH_NONTAKEN_WEIGHT); + setEdgeWeight(BB, TakenIdx, FPH_TAKEN_WEIGHT); + setEdgeWeight(BB, NonTakenIdx, FPH_NONTAKEN_WEIGHT); return true; } +bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) { + InvokeInst *II = dyn_cast(BB->getTerminator()); + if (!II) + return false; -bool BranchProbabilityAnalysis::runOnFunction(Function &F) { + setEdgeWeight(BB, 0/*Index for Normal*/, IH_TAKEN_WEIGHT); + setEdgeWeight(BB, 1/*Index for Unwind*/, IH_NONTAKEN_WEIGHT); + return true; +} - for (Function::iterator I = F.begin(), E = F.end(); I != E; ) { - BasicBlock *BB = I++; +void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired(); + AU.setPreservesAll(); +} - if (calcLoopBranchHeuristics(BB)) +bool BranchProbabilityInfo::runOnFunction(Function &F) { + DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName() + << " ----\n\n"); + LastF = &F; // Store the last function we ran on for printing. + LI = &getAnalysis(); + 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 (po_iterator I = po_begin(&F.getEntryBlock()), + E = po_end(&F.getEntryBlock()); + I != E; ++I) { + DEBUG(dbgs() << "Computing probabilities for " << I->getName() << "\n"); + if (calcUnreachableHeuristics(*I)) continue; - - if (calcReturnHeuristics(BB)) + if (calcMetadataWeights(*I)) continue; - - if (calcPointerHeuristics(BB)) + if (calcColdCallHeuristics(*I)) continue; - - calcZeroHeuristics(BB); + if (calcLoopBranchHeuristics(*I)) + continue; + if (calcPointerHeuristics(*I)) + continue; + if (calcZeroHeuristics(*I)) + continue; + if (calcFloatingPointHeuristics(*I)) + continue; + calcInvokeHeuristics(*I); } + PostDominatedByUnreachable.clear(); + PostDominatedByColdCall.clear(); return false; } -void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired(); - AU.setPreservesAll(); -} - -bool BranchProbabilityInfo::runOnFunction(Function &F) { - LoopInfo &LI = getAnalysis(); - BranchProbabilityAnalysis BPA(&Weights, this, &LI); - return BPA.runOnFunction(F); +void BranchProbabilityInfo::print(raw_ostream &OS, const Module *) 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 (Function::const_iterator BI = LastF->begin(), BE = LastF->end(); + BI != BE; ++BI) { + for (succ_const_iterator SI = succ_begin(BI), SE = succ_end(BI); + SI != SE; ++SI) { + printEdgeProbability(OS << " ", BI, *SI); + } + } } uint32_t BranchProbabilityInfo::getSumForBlock(const BasicBlock *BB) const { uint32_t Sum = 0; for (succ_const_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) { - const BasicBlock *Succ = *I; - uint32_t Weight = getEdgeWeight(BB, Succ); + uint32_t Weight = getEdgeWeight(BB, I.getSuccessorIndex()); uint32_t PrevSum = Sum; Sum += Weight; @@ -383,12 +550,8 @@ uint32_t BranchProbabilityInfo::getSumForBlock(const BasicBlock *BB) const { bool BranchProbabilityInfo:: isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const { // Hot probability is at least 4/5 = 80% - uint32_t Weight = getEdgeWeight(Src, Dst); - uint32_t Sum = getSumForBlock(Src); - - // FIXME: Implement BranchProbability::compare then change this code to - // compare this BranchProbability against a static "hot" BranchProbability. - return (uint64_t)Weight * 5 > (uint64_t)Sum * 4; + // FIXME: Compare against a static "hot" BranchProbability. + return getEdgeProbability(Src, Dst) > BranchProbability(4, 5); } BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const { @@ -410,18 +573,20 @@ BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const { } } - // FIXME: Use BranchProbability::compare. - if ((uint64_t)MaxWeight * 5 > (uint64_t)Sum * 4) + // Hot probability is at least 4/5 = 80% + if (BranchProbability(MaxWeight, Sum) > BranchProbability(4, 5)) return MaxSucc; return 0; } -// Return edge's weight. If can't find it, return DEFAULT_WEIGHT value. +/// Get the raw edge weight for the edge. If can't find it, return +/// DEFAULT_WEIGHT value. Here an edge is specified using PredBlock and an index +/// to the successors. uint32_t BranchProbabilityInfo:: -getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const { - Edge E(Src, Dst); - DenseMap::const_iterator I = Weights.find(E); +getEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors) const { + DenseMap::const_iterator I = + Weights.find(std::make_pair(Src, IndexInSuccessors)); if (I != Weights.end()) return I->second; @@ -429,15 +594,50 @@ getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const { return DEFAULT_WEIGHT; } +uint32_t +BranchProbabilityInfo:: +getEdgeWeight(const BasicBlock *Src, succ_const_iterator Dst) const { + size_t index = std::distance(succ_begin(Src), Dst); + return getEdgeWeight(Src, index); +} + +/// Get the raw edge weight calculated for the block pair. This returns the sum +/// of all raw edge weights from Src to Dst. +uint32_t BranchProbabilityInfo:: +getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const { + uint32_t Weight = 0; + DenseMap::const_iterator MapI; + for (succ_const_iterator I = succ_begin(Src), E = succ_end(Src); I != E; ++I) + if (*I == Dst) { + MapI = Weights.find(std::make_pair(Src, I.getSuccessorIndex())); + if (MapI != Weights.end()) + Weight += MapI->second; + } + return (Weight == 0) ? DEFAULT_WEIGHT : Weight; +} + +/// Set the edge weight for a given edge specified by PredBlock and an index +/// to the successors. void BranchProbabilityInfo:: -setEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst, uint32_t Weight) { - Weights[std::make_pair(Src, Dst)] = Weight; - DEBUG(dbgs() << "set edge " << Src->getNameStr() << " -> " - << Dst->getNameStr() << " weight to " << Weight - << (isEdgeHot(Src, Dst) ? " [is HOT now]\n" : "\n")); +setEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors, + uint32_t Weight) { + Weights[std::make_pair(Src, IndexInSuccessors)] = Weight; + DEBUG(dbgs() << "set edge " << Src->getName() << " -> " + << IndexInSuccessors << " successor weight to " + << Weight << "\n"); } +/// Get an edge's probability, relative to other out-edges from Src. +BranchProbability BranchProbabilityInfo:: +getEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors) const { + uint32_t N = getEdgeWeight(Src, IndexInSuccessors); + uint32_t D = getSumForBlock(Src); + + return BranchProbability(N, D); +} +/// Get the probability of going from Src to Dst. It returns the sum of all +/// probabilities for edges from Src to Dst. BranchProbability BranchProbabilityInfo:: getEdgeProbability(const BasicBlock *Src, const BasicBlock *Dst) const { @@ -448,11 +648,12 @@ getEdgeProbability(const BasicBlock *Src, const BasicBlock *Dst) const { } raw_ostream & -BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS, BasicBlock *Src, - BasicBlock *Dst) const { +BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS, + const BasicBlock *Src, + const BasicBlock *Dst) const { const BranchProbability Prob = getEdgeProbability(Src, Dst); - OS << "edge " << Src->getNameStr() << " -> " << Dst->getNameStr() + OS << "edge " << Src->getName() << " -> " << Dst->getName() << " probability is " << Prob << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");