#include "llvm/Support/BranchProbability.h"
namespace llvm {
-
+class LoopInfo;
class raw_ostream;
class BranchProbabilityInfo : public FunctionPass {
-
- // Default weight value. Used when we don't have information about the edge.
- // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
- // the successors have a weight yet. But it doesn't make sense when providing
- // weight to an edge that may have siblings with non-zero weights. This can
- // be handled various ways, but it's probably fine for an edge with unknown
- // weight to just "inherit" the non-zero weight of an adjacent successor.
- static const uint32_t DEFAULT_WEIGHT = 16;
-
- typedef std::pair<const BasicBlock *, const BasicBlock *> Edge;
-
- DenseMap<Edge, uint32_t> Weights;
-
- /// \brief Track the last function we run over for printing.
- Function *LastF;
-
- // Get sum of the block successors' weights.
- uint32_t getSumForBlock(const BasicBlock *BB) const;
-
public:
static char ID;
// has only one successor.
raw_ostream &printEdgeProbability(raw_ostream &OS, const BasicBlock *Src,
const BasicBlock *Dst) const;
+
+private:
+ typedef std::pair<const BasicBlock *, const BasicBlock *> Edge;
+
+ // Default weight value. Used when we don't have information about the edge.
+ // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of
+ // the successors have a weight yet. But it doesn't make sense when providing
+ // weight to an edge that may have siblings with non-zero weights. This can
+ // be handled various ways, but it's probably fine for an edge with unknown
+ // weight to just "inherit" the non-zero weight of an adjacent successor.
+ static const uint32_t DEFAULT_WEIGHT = 16;
+
+ DenseMap<Edge, uint32_t> Weights;
+
+ /// \brief Handle to the LoopInfo analysis.
+ LoopInfo *LI;
+
+ /// \brief Track the last function we run over for printing.
+ Function *LastF;
+
+ /// \brief Get sum of the block successors' weights.
+ uint32_t getSumForBlock(const BasicBlock *BB) const;
+
+ bool calcMetadataWeights(BasicBlock *BB);
+ bool calcReturnHeuristics(BasicBlock *BB);
+ bool calcPointerHeuristics(BasicBlock *BB);
+ bool calcLoopBranchHeuristics(BasicBlock *BB);
+ bool calcZeroHeuristics(BasicBlock *BB);
+ bool calcFloatingPointHeuristics(BasicBlock *BB);
};
}
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<const BasicBlock *, const BasicBlock *> Edge;
-
- 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;
-
- 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;
-
- // 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;
-
- // Return TRUE if BB leads directly to a Return Instruction.
- static bool isReturningBlock(BasicBlock *BB) {
- SmallPtrSet<BasicBlock *, 8> Visited;
-
- while (true) {
- TerminatorInst *TI = BB->getTerminator();
- if (isa<ReturnInst>(TI))
- return true;
-
- if (TI->getNumSuccessors() > 1)
- break;
-
- // It is unreachable block which we can consider as a return instruction.
- if (TI->getNumSuccessors() == 0)
- return true;
-
- Visited.insert(BB);
- BB = TI->getSuccessor(0);
-
- // Stop if cycle is detected.
- if (Visited.count(BB))
- return false;
- }
+// 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;
- return false;
- }
+static const uint32_t RH_TAKEN_WEIGHT = 24;
+static const uint32_t RH_NONTAKEN_WEIGHT = 8;
- uint32_t getMaxWeightFor(BasicBlock *BB) const {
- return UINT32_MAX / BB->getTerminator()->getNumSuccessors();
- }
+static const uint32_t PH_TAKEN_WEIGHT = 20;
+static const uint32_t PH_NONTAKEN_WEIGHT = 12;
-public:
- BranchProbabilityAnalysis(BranchProbabilityInfo *BP, LoopInfo *LI)
- : BP(BP), LI(LI) {
- }
+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;
+
+// Standard weight value. Used when none of the heuristics set weight for
+// the edge.
+static const uint32_t NORMAL_WEIGHT = 16;
- // Metadata Weights
- bool calcMetadataWeights(BasicBlock *BB);
+// Minimum weight of an edge. Please note, that weight is NEVER 0.
+static const uint32_t MIN_WEIGHT = 1;
- // Return Heuristics
- bool calcReturnHeuristics(BasicBlock *BB);
+// Return TRUE if BB leads directly to a Return Instruction.
+static bool isReturningBlock(BasicBlock *BB) {
+ SmallPtrSet<BasicBlock *, 8> Visited;
- // Pointer Heuristics
- bool calcPointerHeuristics(BasicBlock *BB);
+ while (true) {
+ TerminatorInst *TI = BB->getTerminator();
+ if (isa<ReturnInst>(TI))
+ return true;
- // Loop Branch Heuristics
- bool calcLoopBranchHeuristics(BasicBlock *BB);
+ if (TI->getNumSuccessors() > 1)
+ break;
+
+ // It is unreachable block which we can consider as a return instruction.
+ if (TI->getNumSuccessors() == 0)
+ return true;
+
+ Visited.insert(BB);
+ BB = TI->getSuccessor(0);
- // Zero Heuristics
- bool calcZeroHeuristics(BasicBlock *BB);
+ // Stop if cycle is detected.
+ if (Visited.count(BB))
+ return false;
+ }
- // Floating Point Heuristics
- bool calcFloatingPointHeuristics(BasicBlock *BB);
+ return false;
+}
+
+static uint32_t getMaxWeightFor(BasicBlock *BB) {
+ return UINT32_MAX / BB->getTerminator()->getNumSuccessors();
+}
- bool runOnFunction(Function &F);
-};
-} // end anonymous namespace
// Propagate existing explicit probabilities from either profile data or
// 'expect' intrinsic processing.
-bool BranchProbabilityAnalysis::calcMetadataWeights(BasicBlock *BB) {
+bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) {
TerminatorInst *TI = BB->getTerminator();
if (TI->getNumSuccessors() == 1)
return false;
}
assert(Weights.size() == TI->getNumSuccessors() && "Checked above");
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
- BP->setEdgeWeight(BB, TI->getSuccessor(i), Weights[i]);
+ setEdgeWeight(BB, TI->getSuccessor(i), Weights[i]);
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){
+bool BranchProbabilityInfo::calcReturnHeuristics(BasicBlock *BB){
if (BB->getTerminator()->getNumSuccessors() == 1)
return false;
for (SmallPtrSet<BasicBlock *, 4>::iterator I = StayEdges.begin(),
E = StayEdges.end(); I != E; ++I)
- BP->setEdgeWeight(BB, *I, stayWeight);
+ setEdgeWeight(BB, *I, stayWeight);
}
if (uint32_t numRetEdges = ReturningEdges.size()) {
retWeight = MIN_WEIGHT;
for (SmallPtrSet<BasicBlock *, 4>::iterator I = ReturningEdges.begin(),
E = ReturningEdges.end(); I != E; ++I) {
- BP->setEdgeWeight(BB, *I, retWeight);
+ setEdgeWeight(BB, *I, retWeight);
}
}
// 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<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
if (!isProb)
std::swap(Taken, NonTaken);
- BP->setEdgeWeight(BB, Taken, PH_TAKEN_WEIGHT);
- BP->setEdgeWeight(BB, NonTaken, PH_NONTAKEN_WEIGHT);
+ setEdgeWeight(BB, Taken, PH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, NonTaken, 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) {
+bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB) {
uint32_t numSuccs = BB->getTerminator()->getNumSuccessors();
Loop *L = LI->getLoopFor(BB);
for (SmallPtrSet<BasicBlock *, 8>::iterator EI = BackEdges.begin(),
EE = BackEdges.end(); EI != EE; ++EI) {
BasicBlock *Back = *EI;
- BP->setEdgeWeight(BB, Back, backWeight);
+ setEdgeWeight(BB, Back, backWeight);
}
}
for (SmallPtrSet<BasicBlock *, 8>::iterator EI = InEdges.begin(),
EE = InEdges.end(); EI != EE; ++EI) {
BasicBlock *Back = *EI;
- BP->setEdgeWeight(BB, Back, inWeight);
+ setEdgeWeight(BB, Back, inWeight);
}
}
for (SmallPtrSet<BasicBlock *, 8>::iterator EI = ExitingEdges.begin(),
EE = ExitingEdges.end(); EI != EE; ++EI) {
BasicBlock *Exiting = *EI;
- BP->setEdgeWeight(BB, Exiting, exitWeight);
+ setEdgeWeight(BB, Exiting, exitWeight);
}
}
return true;
}
-bool BranchProbabilityAnalysis::calcZeroHeuristics(BasicBlock *BB) {
+bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) {
BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
if (!isProb)
std::swap(Taken, NonTaken);
- BP->setEdgeWeight(BB, Taken, ZH_TAKEN_WEIGHT);
- BP->setEdgeWeight(BB, NonTaken, ZH_NONTAKEN_WEIGHT);
+ setEdgeWeight(BB, Taken, ZH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, NonTaken, ZH_NONTAKEN_WEIGHT);
return true;
}
-bool BranchProbabilityAnalysis::calcFloatingPointHeuristics(BasicBlock *BB) {
+bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) {
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
if (!isProb)
std::swap(Taken, NonTaken);
- BP->setEdgeWeight(BB, Taken, FPH_TAKEN_WEIGHT);
- BP->setEdgeWeight(BB, NonTaken, FPH_NONTAKEN_WEIGHT);
+ setEdgeWeight(BB, Taken, FPH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, NonTaken, FPH_NONTAKEN_WEIGHT);
return true;
}
-bool BranchProbabilityAnalysis::runOnFunction(Function &F) {
+void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LoopInfo>();
+ AU.setPreservesAll();
+}
+
+bool BranchProbabilityInfo::runOnFunction(Function &F) {
+ LastF = &F; // Store the last function we ran on for printing.
+ LI = &getAnalysis<LoopInfo>();
+
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
if (calcMetadataWeights(I))
continue;
return false;
}
-void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LoopInfo>();
- AU.setPreservesAll();
-}
-
-bool BranchProbabilityInfo::runOnFunction(Function &F) {
- LastF = &F; // Store the last function we ran on for printing.
- LoopInfo &LI = getAnalysis<LoopInfo>();
- BranchProbabilityAnalysis BPA(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,
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