-//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -*- C++ -*-===//
+//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===//
//
// The LLVM Compiler Infrastructure
//
//
//===----------------------------------------------------------------------===//
-#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Metadata.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Support/CFG.h"
+#include "llvm/IR/CFG.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/Debug.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-INITIALIZE_PASS_BEGIN(BranchProbabilityInfo, "branch-prob",
+#define DEBUG_TYPE "branch-prob"
+
+INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
"Branch Probability Analysis", false, true)
-INITIALIZE_PASS_DEPENDENCY(LoopInfo)
-INITIALIZE_PASS_END(BranchProbabilityInfo, "branch-prob",
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
"Branch Probability Analysis", false, true)
-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;
- }
+char BranchProbabilityInfoWrapperPass::ID = 0;
+// 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;
+
+/// \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<UnreachableInst>(TI))
+ PostDominatedByUnreachable.insert(BB);
return false;
}
- uint32_t getMaxWeightFor(BasicBlock *BB) const {
- return UINT32_MAX / BB->getTerminator()->getNumSuccessors();
- }
+ SmallVector<unsigned, 4> UnreachableEdges;
+ SmallVector<unsigned, 4> ReachableEdges;
-public:
- BranchProbabilityAnalysis(BranchProbabilityInfo *BP, LoopInfo *LI)
- : BP(BP), LI(LI) {
+ 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());
}
- // Metadata Weights
- bool calcMetadataWeights(BasicBlock *BB);
-
- // Return Heuristics
- bool calcReturnHeuristics(BasicBlock *BB);
+ // 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);
- // Pointer Heuristics
- bool calcPointerHeuristics(BasicBlock *BB);
-
- // Loop Branch Heuristics
- bool calcLoopBranchHeuristics(BasicBlock *BB);
+ // Skip probabilities if this block has a single successor or if all were
+ // reachable.
+ if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
+ return false;
- // Zero Heuristics
- bool calcZeroHeuristics(BasicBlock *BB);
+ // 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;
+ }
- // Floating Point Heuristics
- bool calcFloatingPointHeuristics(BasicBlock *BB);
+ 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 (ReachableEdges.empty())
+ 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);
- bool runOnFunction(Function &F);
-};
-} // end anonymous namespace
+ return true;
+}
// 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;
if (!WeightsNode)
return false;
+ // Check that the number of successors is manageable.
+ assert(TI->getNumSuccessors() < UINT32_MAX && "Too many successors");
+
// 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;
- // 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);
+ // Build up the final weights that will be used in a temporary buffer.
+ // Compute the sum of all weights to later decide whether they need to
+ // be scaled to fit in 32 bits.
+ uint64_t WeightSum = 0;
SmallVector<uint32_t, 2> Weights;
Weights.reserve(TI->getNumSuccessors());
for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
- ConstantInt *Weight = dyn_cast<ConstantInt>(WeightsNode->getOperand(i));
+ ConstantInt *Weight =
+ mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(i));
if (!Weight)
return false;
- Weights.push_back(
- std::max<uint32_t>(1, Weight->getLimitedValue(WeightLimit)));
+ assert(Weight->getValue().getActiveBits() <= 32 &&
+ "Too many bits for uint32_t");
+ Weights.push_back(Weight->getZExtValue());
+ WeightSum += Weights.back();
}
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]);
+
+ // If the sum of weights does not fit in 32 bits, scale every weight down
+ // accordingly.
+ uint64_t ScalingFactor =
+ (WeightSum > UINT32_MAX) ? WeightSum / UINT32_MAX + 1 : 1;
+
+ WeightSum = 0;
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
+ uint32_t W = Weights[i] / ScalingFactor;
+ WeightSum += W;
+ setEdgeWeight(BB, i, W);
+ }
+ assert(WeightSum <= UINT32_MAX &&
+ "Expected weights to scale down to 32 bits");
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<BasicBlock *, 4> ReturningEdges;
- SmallPtrSet<BasicBlock *, 4> 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<unsigned, 4> ColdEdges;
+ SmallVector<unsigned, 4> 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<CallInst>(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;
-
- for (SmallPtrSet<BasicBlock *, 4>::iterator I = StayEdges.begin(),
- E = StayEdges.end(); I != E; ++I)
- BP->setEdgeWeight(BB, *I, stayWeight);
- }
+ // Skip probabilities if this block has a single successor.
+ if (TI->getNumSuccessors() == 1 || ColdEdges.empty())
+ return false;
- if (uint32_t numRetEdges = ReturningEdges.size()) {
- uint32_t retWeight = RH_NONTAKEN_WEIGHT / numRetEdges;
- if (retWeight < MIN_WEIGHT)
- retWeight = MIN_WEIGHT;
- for (SmallPtrSet<BasicBlock *, 4>::iterator I = ReturningEdges.begin(),
- E = ReturningEdges.end(); I != E; ++I) {
- BP->setEdgeWeight(BB, *I, retWeight);
- }
- }
+ 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())
+ 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);
- 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<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
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();
-
- Loop *L = LI->getLoopFor(BB);
+bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB,
+ const LoopInfo &LI) {
+ Loop *L = LI.getLoopFor(BB);
if (!L)
return false;
- SmallPtrSet<BasicBlock *, 8> BackEdges;
- SmallPtrSet<BasicBlock *, 8> ExitingEdges;
- SmallPtrSet<BasicBlock *, 8> InEdges; // Edges from header to the loop.
-
- bool isHeader = BB == L->getHeader();
+ SmallVector<unsigned, 8> BackEdges;
+ SmallVector<unsigned, 8> ExitingEdges;
+ SmallVector<unsigned, 8> 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 (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;
- for (SmallPtrSet<BasicBlock *, 8>::iterator EI = BackEdges.begin(),
+ for (SmallVectorImpl<unsigned>::iterator EI = BackEdges.begin(),
EE = BackEdges.end(); EI != EE; ++EI) {
- BasicBlock *Back = *EI;
- BP->setEdgeWeight(BB, Back, backWeight);
+ setEdgeWeight(BB, *EI, backWeight);
}
}
if (inWeight < NORMAL_WEIGHT)
inWeight = NORMAL_WEIGHT;
- for (SmallPtrSet<BasicBlock *, 8>::iterator EI = InEdges.begin(),
+ for (SmallVectorImpl<unsigned>::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<BasicBlock *, 8>::iterator EI = ExitingEdges.begin(),
+ for (SmallVectorImpl<unsigned>::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<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
if (!CV)
return false;
+ // If the LHS is the result of AND'ing a value with a single bit bitmask,
+ // we don't have information about probabilities.
+ if (Instruction *LHS = dyn_cast<Instruction>(CI->getOperand(0)))
+ if (LHS->getOpcode() == Instruction::And)
+ if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(LHS->getOperand(1)))
+ if (AndRHS->getUniqueInteger().isPowerOf2())
+ return false;
+
bool isProb;
if (CV->isZero()) {
switch (CI->getPredicate()) {
// InstCombine canonicalizes X <= 0 into X < 1.
// X <= 0 -> Unlikely
isProb = false;
- } else if (CV->isAllOnesValue() && CI->getPredicate() == CmpInst::ICMP_SGT) {
- // InstCombine canonicalizes X >= 0 into X > -1.
- // X >= 0 -> Likely
- isProb = true;
+ } 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;
}
- 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, ZH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, NonTakenIdx, 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;
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, FPH_TAKEN_WEIGHT);
- BP->setEdgeWeight(BB, NonTaken, FPH_NONTAKEN_WEIGHT);
+ setEdgeWeight(BB, TakenIdx, FPH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, NonTakenIdx, FPH_NONTAKEN_WEIGHT);
return true;
}
-bool BranchProbabilityAnalysis::runOnFunction(Function &F) {
-
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
- BasicBlock *BB = I++;
-
- if (calcMetadataWeights(BB))
- continue;
-
- if (calcLoopBranchHeuristics(BB))
- continue;
-
- if (calcReturnHeuristics(BB))
- continue;
-
- if (calcPointerHeuristics(BB))
- continue;
-
- if (calcZeroHeuristics(BB))
- continue;
-
- calcFloatingPointHeuristics(BB);
- }
-
- return false;
-}
+bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
+ InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator());
+ if (!II)
+ return false;
-void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LoopInfo>();
- AU.setPreservesAll();
+ setEdgeWeight(BB, 0/*Index for Normal*/, IH_TAKEN_WEIGHT);
+ setEdgeWeight(BB, 1/*Index for Unwind*/, IH_NONTAKEN_WEIGHT);
+ return true;
}
-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::releaseMemory() {
+ Weights.clear();
}
-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 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;
- assert(Sum > PrevSum); (void) PrevSum;
+ assert(Sum >= PrevSum); (void) PrevSum;
}
return Sum;
BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const {
uint32_t Sum = 0;
uint32_t MaxWeight = 0;
- BasicBlock *MaxSucc = 0;
+ BasicBlock *MaxSucc = nullptr;
for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
BasicBlock *Succ = *I;
if (BranchProbability(MaxWeight, Sum) > BranchProbability(4, 5))
return MaxSucc;
- return 0;
+ return nullptr;
}
-// 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<Edge, uint32_t>::const_iterator I = Weights.find(E);
+getEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors) const {
+ DenseMap<Edge, uint32_t>::const_iterator I =
+ Weights.find(std::make_pair(Src, IndexInSuccessors));
if (I != Weights.end())
return I->second;
return DEFAULT_WEIGHT;
}
+uint32_t BranchProbabilityInfo::getEdgeWeight(const BasicBlock *Src,
+ succ_const_iterator Dst) const {
+ return getEdgeWeight(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;
+ 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;
+ }
+ }
+ 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, 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);
+ // It is possible that the edge weight on the only successor edge of Src is
+ // zero, in which case we return 100%.
+ if (N == 0 && D == 0)
+ return BranchProbability::getOne();
+
+ 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 {
uint32_t N = getEdgeWeight(Src, Dst);
uint32_t D = getSumForBlock(Src);
+ // It is possible that the edge weight on the only successor edge of Src is
+ // zero, in which case we return 100%.
+ if (N == 0 && D == 0)
+ return BranchProbability::getOne();
+
return BranchProbability(N, D);
}
+BranchProbability
+BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
+ succ_const_iterator Dst) const {
+ return getEdgeProbability(Src, Dst.getSuccessorIndex());
+}
+
raw_ostream &
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");
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