#define DEBUG_TYPE "branch-prob"
-INITIALIZE_PASS_BEGIN(BranchProbabilityInfo, "branch-prob",
+INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
"Branch Probability Analysis", false, true)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
-INITIALIZE_PASS_END(BranchProbabilityInfo, "branch-prob",
+INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
"Branch Probability Analysis", false, true)
-char BranchProbabilityInfo::ID = 0;
+char BranchProbabilityInfoWrapperPass::ID = 0;
// Weights are for internal use only. They are used by heuristics to help to
// estimate edges' probability. Example:
/// 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;
-
/// \brief Calculate edge weights for successors lead to unreachable.
///
/// Predict that a successor which leads necessarily to an
if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
return false;
- uint32_t UnreachableWeight =
- std::max(UR_TAKEN_WEIGHT / (unsigned)UnreachableEdges.size(), MIN_WEIGHT);
- for (SmallVectorImpl<unsigned>::iterator I = UnreachableEdges.begin(),
- E = UnreachableEdges.end();
- I != E; ++I)
- setEdgeWeight(BB, *I, UnreachableWeight);
+ // If the terminator is an InvokeInst, check only the normal destination block
+ // as the unwind edge of InvokeInst is also very unlikely taken.
+ if (auto *II = dyn_cast<InvokeInst>(TI))
+ if (PostDominatedByUnreachable.count(II->getNormalDest())) {
+ PostDominatedByUnreachable.insert(BB);
+ // Return false here so that edge weights for InvokeInst could be decided
+ // in calcInvokeHeuristics().
+ return false;
+ }
- if (ReachableEdges.empty())
+ if (ReachableEdges.empty()) {
+ BranchProbability Prob(1, UnreachableEdges.size());
+ for (unsigned SuccIdx : UnreachableEdges)
+ setEdgeProbability(BB, SuccIdx, Prob);
return true;
- uint32_t ReachableWeight =
- std::max(UR_NONTAKEN_WEIGHT / (unsigned)ReachableEdges.size(),
- NORMAL_WEIGHT);
- for (SmallVectorImpl<unsigned>::iterator I = ReachableEdges.begin(),
- E = ReachableEdges.end();
- I != E; ++I)
- setEdgeWeight(BB, *I, ReachableWeight);
+ }
+
+ BranchProbability UnreachableProb(UR_TAKEN_WEIGHT,
+ (UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
+ UnreachableEdges.size());
+ BranchProbability ReachableProb(UR_NONTAKEN_WEIGHT,
+ (UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
+ ReachableEdges.size());
+
+ for (unsigned SuccIdx : UnreachableEdges)
+ setEdgeProbability(BB, SuccIdx, UnreachableProb);
+ for (unsigned SuccIdx : ReachableEdges)
+ setEdgeProbability(BB, SuccIdx, ReachableProb);
return true;
}
WeightSum = 0;
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
- uint32_t W = Weights[i] / ScalingFactor;
- WeightSum += W;
- setEdgeWeight(BB, i, W);
+ Weights[i] /= ScalingFactor;
+ WeightSum += Weights[i];
}
+
+ if (WeightSum == 0) {
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ setEdgeProbability(BB, i, {1, e});
+ } else {
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ setEdgeProbability(BB, i, {Weights[i], static_cast<uint32_t>(WeightSum)});
+ }
+
assert(WeightSum <= UINT32_MAX &&
"Expected weights to scale down to 32 bits");
if (TI->getNumSuccessors() == 1 || ColdEdges.empty())
return false;
- uint32_t ColdWeight =
- std::max(CC_TAKEN_WEIGHT / (unsigned) ColdEdges.size(), MIN_WEIGHT);
- for (SmallVectorImpl<unsigned>::iterator I = ColdEdges.begin(),
- E = ColdEdges.end();
- I != E; ++I)
- setEdgeWeight(BB, *I, ColdWeight);
-
- if (NormalEdges.empty())
+ if (NormalEdges.empty()) {
+ BranchProbability Prob(1, ColdEdges.size());
+ for (unsigned SuccIdx : ColdEdges)
+ setEdgeProbability(BB, SuccIdx, Prob);
return true;
- uint32_t NormalWeight = std::max(
- CC_NONTAKEN_WEIGHT / (unsigned) NormalEdges.size(), NORMAL_WEIGHT);
- for (SmallVectorImpl<unsigned>::iterator I = NormalEdges.begin(),
- E = NormalEdges.end();
- I != E; ++I)
- setEdgeWeight(BB, *I, NormalWeight);
+ }
+
+ BranchProbability ColdProb(CC_TAKEN_WEIGHT,
+ (CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
+ ColdEdges.size());
+ BranchProbability NormalProb(CC_NONTAKEN_WEIGHT,
+ (CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
+ NormalEdges.size());
+
+ for (unsigned SuccIdx : ColdEdges)
+ setEdgeProbability(BB, SuccIdx, ColdProb);
+ for (unsigned SuccIdx : NormalEdges)
+ setEdgeProbability(BB, SuccIdx, NormalProb);
return true;
}
if (!isProb)
std::swap(TakenIdx, NonTakenIdx);
- setEdgeWeight(BB, TakenIdx, PH_TAKEN_WEIGHT);
- setEdgeWeight(BB, NonTakenIdx, PH_NONTAKEN_WEIGHT);
+ BranchProbability TakenProb(PH_TAKEN_WEIGHT,
+ PH_TAKEN_WEIGHT + PH_NONTAKEN_WEIGHT);
+ setEdgeProbability(BB, TakenIdx, TakenProb);
+ setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
return true;
}
// Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
// as taken, exiting edges as not-taken.
-bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB) {
- Loop *L = LI->getLoopFor(BB);
+bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB,
+ const LoopInfo &LI) {
+ Loop *L = LI.getLoopFor(BB);
if (!L)
return false;
if (BackEdges.empty() && ExitingEdges.empty())
return false;
- if (uint32_t numBackEdges = BackEdges.size()) {
- uint32_t backWeight = LBH_TAKEN_WEIGHT / numBackEdges;
- if (backWeight < NORMAL_WEIGHT)
- backWeight = NORMAL_WEIGHT;
+ // Collect the sum of probabilities of back-edges/in-edges/exiting-edges, and
+ // normalize them so that they sum up to one.
+ SmallVector<BranchProbability, 4> Probs(3, BranchProbability::getZero());
+ unsigned Denom = (BackEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
+ (InEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
+ (ExitingEdges.empty() ? 0 : LBH_NONTAKEN_WEIGHT);
+ if (!BackEdges.empty())
+ Probs[0] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
+ if (!InEdges.empty())
+ Probs[1] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
+ if (!ExitingEdges.empty())
+ Probs[2] = BranchProbability(LBH_NONTAKEN_WEIGHT, Denom);
- for (SmallVectorImpl<unsigned>::iterator EI = BackEdges.begin(),
- EE = BackEdges.end(); EI != EE; ++EI) {
- setEdgeWeight(BB, *EI, backWeight);
- }
+ if (uint32_t numBackEdges = BackEdges.size()) {
+ auto Prob = Probs[0] / numBackEdges;
+ for (unsigned SuccIdx : BackEdges)
+ setEdgeProbability(BB, SuccIdx, Prob);
}
if (uint32_t numInEdges = InEdges.size()) {
- uint32_t inWeight = LBH_TAKEN_WEIGHT / numInEdges;
- if (inWeight < NORMAL_WEIGHT)
- inWeight = NORMAL_WEIGHT;
-
- for (SmallVectorImpl<unsigned>::iterator EI = InEdges.begin(),
- EE = InEdges.end(); EI != EE; ++EI) {
- setEdgeWeight(BB, *EI, inWeight);
- }
+ auto Prob = Probs[1] / numInEdges;
+ for (unsigned SuccIdx : InEdges)
+ setEdgeProbability(BB, SuccIdx, Prob);
}
if (uint32_t numExitingEdges = ExitingEdges.size()) {
- uint32_t exitWeight = LBH_NONTAKEN_WEIGHT / numExitingEdges;
- if (exitWeight < MIN_WEIGHT)
- exitWeight = MIN_WEIGHT;
-
- for (SmallVectorImpl<unsigned>::iterator EI = ExitingEdges.begin(),
- EE = ExitingEdges.end(); EI != EE; ++EI) {
- setEdgeWeight(BB, *EI, exitWeight);
- }
+ auto Prob = Probs[2] / numExitingEdges;
+ for (unsigned SuccIdx : ExitingEdges)
+ setEdgeProbability(BB, SuccIdx, Prob);
}
return true;
if (!isProb)
std::swap(TakenIdx, NonTakenIdx);
- setEdgeWeight(BB, TakenIdx, ZH_TAKEN_WEIGHT);
- setEdgeWeight(BB, NonTakenIdx, ZH_NONTAKEN_WEIGHT);
-
+ BranchProbability TakenProb(ZH_TAKEN_WEIGHT,
+ ZH_TAKEN_WEIGHT + ZH_NONTAKEN_WEIGHT);
+ setEdgeProbability(BB, TakenIdx, TakenProb);
+ setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
return true;
}
if (!isProb)
std::swap(TakenIdx, NonTakenIdx);
- setEdgeWeight(BB, TakenIdx, FPH_TAKEN_WEIGHT);
- setEdgeWeight(BB, NonTakenIdx, FPH_NONTAKEN_WEIGHT);
-
+ BranchProbability TakenProb(FPH_TAKEN_WEIGHT,
+ FPH_TAKEN_WEIGHT + FPH_NONTAKEN_WEIGHT);
+ setEdgeProbability(BB, TakenIdx, TakenProb);
+ setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
return true;
}
if (!II)
return false;
- setEdgeWeight(BB, 0/*Index for Normal*/, IH_TAKEN_WEIGHT);
- setEdgeWeight(BB, 1/*Index for Unwind*/, IH_NONTAKEN_WEIGHT);
+ 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::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LoopInfoWrapperPass>();
- AU.setPreservesAll();
+void BranchProbabilityInfo::releaseMemory() {
+ Probs.clear();
}
-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<LoopInfoWrapperPass>().getLoopInfo();
- 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))
- continue;
- if (calcPointerHeuristics(BB))
- continue;
- if (calcZeroHeuristics(BB))
- continue;
- if (calcFloatingPointHeuristics(BB))
- continue;
- calcInvokeHeuristics(BB);
- }
-
- PostDominatedByUnreachable.clear();
- PostDominatedByColdCall.clear();
- return false;
-}
-
-void BranchProbabilityInfo::print(raw_ostream &OS, const Module *) const {
+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 (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);
+ for (const auto &BI : *LastF) {
+ 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) {
- uint32_t Weight = getEdgeWeight(BB, I.getSuccessorIndex());
- uint32_t PrevSum = Sum;
-
- Sum += Weight;
- assert(Sum >= PrevSum); (void) PrevSum;
- }
-
- return Sum;
-}
-
bool BranchProbabilityInfo::
isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const {
// Hot probability is at least 4/5 = 80%
}
BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const {
- uint32_t Sum = 0;
- uint32_t MaxWeight = 0;
+ auto MaxProb = BranchProbability::getZero();
BasicBlock *MaxSucc = nullptr;
for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
BasicBlock *Succ = *I;
- uint32_t Weight = getEdgeWeight(BB, Succ);
- uint32_t PrevSum = Sum;
-
- Sum += Weight;
- assert(Sum > PrevSum); (void) PrevSum;
-
- if (Weight > MaxWeight) {
- MaxWeight = Weight;
+ auto Prob = getEdgeProbability(BB, Succ);
+ if (Prob > MaxProb) {
+ MaxProb = Prob;
MaxSucc = Succ;
}
}
// Hot probability is at least 4/5 = 80%
- if (BranchProbability(MaxWeight, Sum) > BranchProbability(4, 5))
+ if (MaxProb > BranchProbability(4, 5))
return MaxSucc;
return nullptr;
}
-/// 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, unsigned IndexInSuccessors) const {
- DenseMap<Edge, uint32_t>::const_iterator I =
- Weights.find(std::make_pair(Src, IndexInSuccessors));
+/// 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 != Weights.end())
+ if (I != Probs.end())
return I->second;
- return DEFAULT_WEIGHT;
+ return {1,
+ static_cast<uint32_t>(std::distance(succ_begin(Src), succ_end(Src)))};
}
-uint32_t BranchProbabilityInfo::getEdgeWeight(const BasicBlock *Src,
- succ_const_iterator Dst) const {
- return getEdgeWeight(Src, Dst.getSuccessorIndex());
+BranchProbability
+BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
+ succ_const_iterator Dst) const {
+ return getEdgeProbability(Src, Dst.getSuccessorIndex());
}
-/// 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;
- bool FoundWeight = false;
- DenseMap<Edge, uint32_t>::const_iterator MapI;
+/// 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) {
- MapI = Weights.find(std::make_pair(Src, I.getSuccessorIndex()));
- if (MapI != Weights.end()) {
- FoundWeight = true;
- Weight += MapI->second;
+ auto MapI = Probs.find(std::make_pair(Src, I.getSuccessorIndex()));
+ if (MapI != Probs.end()) {
+ FoundProb = true;
+ Prob += MapI->second;
}
}
- return (!FoundWeight) ? 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, 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);
+ uint32_t succ_num = std::distance(succ_begin(Src), succ_end(Src));
+ return FoundProb ? Prob : BranchProbability(1, succ_num);
}
-/// 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 {
-
- uint32_t N = getEdgeWeight(Src, Dst);
- uint32_t D = getSumForBlock(Src);
-
- return BranchProbability(N, D);
+/// 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 &
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);
+}
projects / oota-llvm.git / blobdiff