1//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// Loops should be simplified before this analysis.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Analysis/BranchProbabilityInfo.h"
15#include "llvm/ADT/PostOrderIterator.h"
16#include "llvm/Analysis/LoopInfo.h"
17#include "llvm/IR/CFG.h"
18#include "llvm/IR/Constants.h"
19#include "llvm/IR/Function.h"
20#include "llvm/IR/Instructions.h"
21#include "llvm/IR/LLVMContext.h"
22#include "llvm/IR/Metadata.h"
23#include "llvm/Support/Debug.h"
24
25using namespace llvm;
26
27#define DEBUG_TYPE "branch-prob"
28
29INITIALIZE_PASS_BEGIN(BranchProbabilityInfo, "branch-prob",
30                      "Branch Probability Analysis", false, true)
31INITIALIZE_PASS_DEPENDENCY(LoopInfo)
32INITIALIZE_PASS_END(BranchProbabilityInfo, "branch-prob",
33                    "Branch Probability Analysis", false, true)
34
35char BranchProbabilityInfo::ID = 0;
36
37// Weights are for internal use only. They are used by heuristics to help to
38// estimate edges' probability. Example:
39//
40// Using "Loop Branch Heuristics" we predict weights of edges for the
41// block BB2.
42//         ...
43//          |
44//          V
45//         BB1<-+
46//          |   |
47//          |   | (Weight = 124)
48//          V   |
49//         BB2--+
50//          |
51//          | (Weight = 4)
52//          V
53//         BB3
54//
55// Probability of the edge BB2->BB1 = 124 / (124 + 4) = 0.96875
56// Probability of the edge BB2->BB3 = 4 / (124 + 4) = 0.03125
57static const uint32_t LBH_TAKEN_WEIGHT = 124;
58static const uint32_t LBH_NONTAKEN_WEIGHT = 4;
59
60/// \brief Unreachable-terminating branch taken weight.
61///
62/// This is the weight for a branch being taken to a block that terminates
63/// (eventually) in unreachable. These are predicted as unlikely as possible.
64static const uint32_t UR_TAKEN_WEIGHT = 1;
65
66/// \brief Unreachable-terminating branch not-taken weight.
67///
68/// This is the weight for a branch not being taken toward a block that
69/// terminates (eventually) in unreachable. Such a branch is essentially never
70/// taken. Set the weight to an absurdly high value so that nested loops don't
71/// easily subsume it.
72static const uint32_t UR_NONTAKEN_WEIGHT = 1024*1024 - 1;
73
74/// \brief Weight for a branch taken going into a cold block.
75///
76/// This is the weight for a branch taken toward a block marked
77/// cold.  A block is marked cold if it's postdominated by a
78/// block containing a call to a cold function.  Cold functions
79/// are those marked with attribute 'cold'.
80static const uint32_t CC_TAKEN_WEIGHT = 4;
81
82/// \brief Weight for a branch not-taken into a cold block.
83///
84/// This is the weight for a branch not taken toward a block marked
85/// cold.
86static const uint32_t CC_NONTAKEN_WEIGHT = 64;
87
88static const uint32_t PH_TAKEN_WEIGHT = 20;
89static const uint32_t PH_NONTAKEN_WEIGHT = 12;
90
91static const uint32_t ZH_TAKEN_WEIGHT = 20;
92static const uint32_t ZH_NONTAKEN_WEIGHT = 12;
93
94static const uint32_t FPH_TAKEN_WEIGHT = 20;
95static const uint32_t FPH_NONTAKEN_WEIGHT = 12;
96
97/// \brief Invoke-terminating normal branch taken weight
98///
99/// This is the weight for branching to the normal destination of an invoke
100/// instruction. We expect this to happen most of the time. Set the weight to an
101/// absurdly high value so that nested loops subsume it.
102static const uint32_t IH_TAKEN_WEIGHT = 1024 * 1024 - 1;
103
104/// \brief Invoke-terminating normal branch not-taken weight.
105///
106/// This is the weight for branching to the unwind destination of an invoke
107/// instruction. This is essentially never taken.
108static const uint32_t IH_NONTAKEN_WEIGHT = 1;
109
110// Standard weight value. Used when none of the heuristics set weight for
111// the edge.
112static const uint32_t NORMAL_WEIGHT = 16;
113
114// Minimum weight of an edge. Please note, that weight is NEVER 0.
115static const uint32_t MIN_WEIGHT = 1;
116
117static uint32_t getMaxWeightFor(BasicBlock *BB) {
118  return UINT32_MAX / BB->getTerminator()->getNumSuccessors();
119}
120
121
122/// \brief Calculate edge weights for successors lead to unreachable.
123///
124/// Predict that a successor which leads necessarily to an
125/// unreachable-terminated block as extremely unlikely.
126bool BranchProbabilityInfo::calcUnreachableHeuristics(BasicBlock *BB) {
127  TerminatorInst *TI = BB->getTerminator();
128  if (TI->getNumSuccessors() == 0) {
129    if (isa<UnreachableInst>(TI))
130      PostDominatedByUnreachable.insert(BB);
131    return false;
132  }
133
134  SmallVector<unsigned, 4> UnreachableEdges;
135  SmallVector<unsigned, 4> ReachableEdges;
136
137  for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
138    if (PostDominatedByUnreachable.count(*I))
139      UnreachableEdges.push_back(I.getSuccessorIndex());
140    else
141      ReachableEdges.push_back(I.getSuccessorIndex());
142  }
143
144  // If all successors are in the set of blocks post-dominated by unreachable,
145  // this block is too.
146  if (UnreachableEdges.size() == TI->getNumSuccessors())
147    PostDominatedByUnreachable.insert(BB);
148
149  // Skip probabilities if this block has a single successor or if all were
150  // reachable.
151  if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
152    return false;
153
154  uint32_t UnreachableWeight =
155    std::max(UR_TAKEN_WEIGHT / (unsigned)UnreachableEdges.size(), MIN_WEIGHT);
156  for (SmallVectorImpl<unsigned>::iterator I = UnreachableEdges.begin(),
157                                           E = UnreachableEdges.end();
158       I != E; ++I)
159    setEdgeWeight(BB, *I, UnreachableWeight);
160
161  if (ReachableEdges.empty())
162    return true;
163  uint32_t ReachableWeight =
164    std::max(UR_NONTAKEN_WEIGHT / (unsigned)ReachableEdges.size(),
165             NORMAL_WEIGHT);
166  for (SmallVectorImpl<unsigned>::iterator I = ReachableEdges.begin(),
167                                           E = ReachableEdges.end();
168       I != E; ++I)
169    setEdgeWeight(BB, *I, ReachableWeight);
170
171  return true;
172}
173
174// Propagate existing explicit probabilities from either profile data or
175// 'expect' intrinsic processing.
176bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) {
177  TerminatorInst *TI = BB->getTerminator();
178  if (TI->getNumSuccessors() == 1)
179    return false;
180  if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
181    return false;
182
183  MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
184  if (!WeightsNode)
185    return false;
186
187  // Ensure there are weights for all of the successors. Note that the first
188  // operand to the metadata node is a name, not a weight.
189  if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1)
190    return false;
191
192  // Build up the final weights that will be used in a temporary buffer, but
193  // don't add them until all weihts are present. Each weight value is clamped
194  // to [1, getMaxWeightFor(BB)].
195  uint32_t WeightLimit = getMaxWeightFor(BB);
196  SmallVector<uint32_t, 2> Weights;
197  Weights.reserve(TI->getNumSuccessors());
198  for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
199    ConstantInt *Weight = dyn_cast<ConstantInt>(WeightsNode->getOperand(i));
200    if (!Weight)
201      return false;
202    Weights.push_back(
203      std::max<uint32_t>(1, Weight->getLimitedValue(WeightLimit)));
204  }
205  assert(Weights.size() == TI->getNumSuccessors() && "Checked above");
206  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
207    setEdgeWeight(BB, i, Weights[i]);
208
209  return true;
210}
211
212/// \brief Calculate edge weights for edges leading to cold blocks.
213///
214/// A cold block is one post-dominated by  a block with a call to a
215/// cold function.  Those edges are unlikely to be taken, so we give
216/// them relatively low weight.
217///
218/// Return true if we could compute the weights for cold edges.
219/// Return false, otherwise.
220bool BranchProbabilityInfo::calcColdCallHeuristics(BasicBlock *BB) {
221  TerminatorInst *TI = BB->getTerminator();
222  if (TI->getNumSuccessors() == 0)
223    return false;
224
225  // Determine which successors are post-dominated by a cold block.
226  SmallVector<unsigned, 4> ColdEdges;
227  SmallVector<unsigned, 4> NormalEdges;
228  for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I)
229    if (PostDominatedByColdCall.count(*I))
230      ColdEdges.push_back(I.getSuccessorIndex());
231    else
232      NormalEdges.push_back(I.getSuccessorIndex());
233
234  // If all successors are in the set of blocks post-dominated by cold calls,
235  // this block is in the set post-dominated by cold calls.
236  if (ColdEdges.size() == TI->getNumSuccessors())
237    PostDominatedByColdCall.insert(BB);
238  else {
239    // Otherwise, if the block itself contains a cold function, add it to the
240    // set of blocks postdominated by a cold call.
241    assert(!PostDominatedByColdCall.count(BB));
242    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
243      if (CallInst *CI = dyn_cast<CallInst>(I))
244        if (CI->hasFnAttr(Attribute::Cold)) {
245          PostDominatedByColdCall.insert(BB);
246          break;
247        }
248  }
249
250  // Skip probabilities if this block has a single successor.
251  if (TI->getNumSuccessors() == 1 || ColdEdges.empty())
252    return false;
253
254  uint32_t ColdWeight =
255      std::max(CC_TAKEN_WEIGHT / (unsigned) ColdEdges.size(), MIN_WEIGHT);
256  for (SmallVectorImpl<unsigned>::iterator I = ColdEdges.begin(),
257                                           E = ColdEdges.end();
258       I != E; ++I)
259    setEdgeWeight(BB, *I, ColdWeight);
260
261  if (NormalEdges.empty())
262    return true;
263  uint32_t NormalWeight = std::max(
264      CC_NONTAKEN_WEIGHT / (unsigned) NormalEdges.size(), NORMAL_WEIGHT);
265  for (SmallVectorImpl<unsigned>::iterator I = NormalEdges.begin(),
266                                           E = NormalEdges.end();
267       I != E; ++I)
268    setEdgeWeight(BB, *I, NormalWeight);
269
270  return true;
271}
272
273// Calculate Edge Weights using "Pointer Heuristics". Predict a comparsion
274// between two pointer or pointer and NULL will fail.
275bool BranchProbabilityInfo::calcPointerHeuristics(BasicBlock *BB) {
276  BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
277  if (!BI || !BI->isConditional())
278    return false;
279
280  Value *Cond = BI->getCondition();
281  ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
282  if (!CI || !CI->isEquality())
283    return false;
284
285  Value *LHS = CI->getOperand(0);
286
287  if (!LHS->getType()->isPointerTy())
288    return false;
289
290  assert(CI->getOperand(1)->getType()->isPointerTy());
291
292  // p != 0   ->   isProb = true
293  // p == 0   ->   isProb = false
294  // p != q   ->   isProb = true
295  // p == q   ->   isProb = false;
296  unsigned TakenIdx = 0, NonTakenIdx = 1;
297  bool isProb = CI->getPredicate() == ICmpInst::ICMP_NE;
298  if (!isProb)
299    std::swap(TakenIdx, NonTakenIdx);
300
301  setEdgeWeight(BB, TakenIdx, PH_TAKEN_WEIGHT);
302  setEdgeWeight(BB, NonTakenIdx, PH_NONTAKEN_WEIGHT);
303  return true;
304}
305
306// Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
307// as taken, exiting edges as not-taken.
308bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB) {
309  Loop *L = LI->getLoopFor(BB);
310  if (!L)
311    return false;
312
313  SmallVector<unsigned, 8> BackEdges;
314  SmallVector<unsigned, 8> ExitingEdges;
315  SmallVector<unsigned, 8> InEdges; // Edges from header to the loop.
316
317  for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
318    if (!L->contains(*I))
319      ExitingEdges.push_back(I.getSuccessorIndex());
320    else if (L->getHeader() == *I)
321      BackEdges.push_back(I.getSuccessorIndex());
322    else
323      InEdges.push_back(I.getSuccessorIndex());
324  }
325
326  if (BackEdges.empty() && ExitingEdges.empty())
327    return false;
328
329  if (uint32_t numBackEdges = BackEdges.size()) {
330    uint32_t backWeight = LBH_TAKEN_WEIGHT / numBackEdges;
331    if (backWeight < NORMAL_WEIGHT)
332      backWeight = NORMAL_WEIGHT;
333
334    for (SmallVectorImpl<unsigned>::iterator EI = BackEdges.begin(),
335         EE = BackEdges.end(); EI != EE; ++EI) {
336      setEdgeWeight(BB, *EI, backWeight);
337    }
338  }
339
340  if (uint32_t numInEdges = InEdges.size()) {
341    uint32_t inWeight = LBH_TAKEN_WEIGHT / numInEdges;
342    if (inWeight < NORMAL_WEIGHT)
343      inWeight = NORMAL_WEIGHT;
344
345    for (SmallVectorImpl<unsigned>::iterator EI = InEdges.begin(),
346         EE = InEdges.end(); EI != EE; ++EI) {
347      setEdgeWeight(BB, *EI, inWeight);
348    }
349  }
350
351  if (uint32_t numExitingEdges = ExitingEdges.size()) {
352    uint32_t exitWeight = LBH_NONTAKEN_WEIGHT / numExitingEdges;
353    if (exitWeight < MIN_WEIGHT)
354      exitWeight = MIN_WEIGHT;
355
356    for (SmallVectorImpl<unsigned>::iterator EI = ExitingEdges.begin(),
357         EE = ExitingEdges.end(); EI != EE; ++EI) {
358      setEdgeWeight(BB, *EI, exitWeight);
359    }
360  }
361
362  return true;
363}
364
365bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) {
366  BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
367  if (!BI || !BI->isConditional())
368    return false;
369
370  Value *Cond = BI->getCondition();
371  ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
372  if (!CI)
373    return false;
374
375  Value *RHS = CI->getOperand(1);
376  ConstantInt *CV = dyn_cast<ConstantInt>(RHS);
377  if (!CV)
378    return false;
379
380  bool isProb;
381  if (CV->isZero()) {
382    switch (CI->getPredicate()) {
383    case CmpInst::ICMP_EQ:
384      // X == 0   ->  Unlikely
385      isProb = false;
386      break;
387    case CmpInst::ICMP_NE:
388      // X != 0   ->  Likely
389      isProb = true;
390      break;
391    case CmpInst::ICMP_SLT:
392      // X < 0   ->  Unlikely
393      isProb = false;
394      break;
395    case CmpInst::ICMP_SGT:
396      // X > 0   ->  Likely
397      isProb = true;
398      break;
399    default:
400      return false;
401    }
402  } else if (CV->isOne() && CI->getPredicate() == CmpInst::ICMP_SLT) {
403    // InstCombine canonicalizes X <= 0 into X < 1.
404    // X <= 0   ->  Unlikely
405    isProb = false;
406  } else if (CV->isAllOnesValue()) {
407    switch (CI->getPredicate()) {
408    case CmpInst::ICMP_EQ:
409      // X == -1  ->  Unlikely
410      isProb = false;
411      break;
412    case CmpInst::ICMP_NE:
413      // X != -1  ->  Likely
414      isProb = true;
415      break;
416    case CmpInst::ICMP_SGT:
417      // InstCombine canonicalizes X >= 0 into X > -1.
418      // X >= 0   ->  Likely
419      isProb = true;
420      break;
421    default:
422      return false;
423    }
424  } else {
425    return false;
426  }
427
428  unsigned TakenIdx = 0, NonTakenIdx = 1;
429
430  if (!isProb)
431    std::swap(TakenIdx, NonTakenIdx);
432
433  setEdgeWeight(BB, TakenIdx, ZH_TAKEN_WEIGHT);
434  setEdgeWeight(BB, NonTakenIdx, ZH_NONTAKEN_WEIGHT);
435
436  return true;
437}
438
439bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) {
440  BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
441  if (!BI || !BI->isConditional())
442    return false;
443
444  Value *Cond = BI->getCondition();
445  FCmpInst *FCmp = dyn_cast<FCmpInst>(Cond);
446  if (!FCmp)
447    return false;
448
449  bool isProb;
450  if (FCmp->isEquality()) {
451    // f1 == f2 -> Unlikely
452    // f1 != f2 -> Likely
453    isProb = !FCmp->isTrueWhenEqual();
454  } else if (FCmp->getPredicate() == FCmpInst::FCMP_ORD) {
455    // !isnan -> Likely
456    isProb = true;
457  } else if (FCmp->getPredicate() == FCmpInst::FCMP_UNO) {
458    // isnan -> Unlikely
459    isProb = false;
460  } else {
461    return false;
462  }
463
464  unsigned TakenIdx = 0, NonTakenIdx = 1;
465
466  if (!isProb)
467    std::swap(TakenIdx, NonTakenIdx);
468
469  setEdgeWeight(BB, TakenIdx, FPH_TAKEN_WEIGHT);
470  setEdgeWeight(BB, NonTakenIdx, FPH_NONTAKEN_WEIGHT);
471
472  return true;
473}
474
475bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
476  InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator());
477  if (!II)
478    return false;
479
480  setEdgeWeight(BB, 0/*Index for Normal*/, IH_TAKEN_WEIGHT);
481  setEdgeWeight(BB, 1/*Index for Unwind*/, IH_NONTAKEN_WEIGHT);
482  return true;
483}
484
485void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
486  AU.addRequired<LoopInfo>();
487  AU.setPreservesAll();
488}
489
490bool BranchProbabilityInfo::runOnFunction(Function &F) {
491  DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
492               << " ----\n\n");
493  LastF = &F; // Store the last function we ran on for printing.
494  LI = &getAnalysis<LoopInfo>();
495  assert(PostDominatedByUnreachable.empty());
496  assert(PostDominatedByColdCall.empty());
497
498  // Walk the basic blocks in post-order so that we can build up state about
499  // the successors of a block iteratively.
500  for (po_iterator<BasicBlock *> I = po_begin(&F.getEntryBlock()),
501                                 E = po_end(&F.getEntryBlock());
502       I != E; ++I) {
503    DEBUG(dbgs() << "Computing probabilities for " << I->getName() << "\n");
504    if (calcUnreachableHeuristics(*I))
505      continue;
506    if (calcMetadataWeights(*I))
507      continue;
508    if (calcColdCallHeuristics(*I))
509      continue;
510    if (calcLoopBranchHeuristics(*I))
511      continue;
512    if (calcPointerHeuristics(*I))
513      continue;
514    if (calcZeroHeuristics(*I))
515      continue;
516    if (calcFloatingPointHeuristics(*I))
517      continue;
518    calcInvokeHeuristics(*I);
519  }
520
521  PostDominatedByUnreachable.clear();
522  PostDominatedByColdCall.clear();
523  return false;
524}
525
526void BranchProbabilityInfo::print(raw_ostream &OS, const Module *) const {
527  OS << "---- Branch Probabilities ----\n";
528  // We print the probabilities from the last function the analysis ran over,
529  // or the function it is currently running over.
530  assert(LastF && "Cannot print prior to running over a function");
531  for (Function::const_iterator BI = LastF->begin(), BE = LastF->end();
532       BI != BE; ++BI) {
533    for (succ_const_iterator SI = succ_begin(BI), SE = succ_end(BI);
534         SI != SE; ++SI) {
535      printEdgeProbability(OS << "  ", BI, *SI);
536    }
537  }
538}
539
540uint32_t BranchProbabilityInfo::getSumForBlock(const BasicBlock *BB) const {
541  uint32_t Sum = 0;
542
543  for (succ_const_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
544    uint32_t Weight = getEdgeWeight(BB, I.getSuccessorIndex());
545    uint32_t PrevSum = Sum;
546
547    Sum += Weight;
548    assert(Sum > PrevSum); (void) PrevSum;
549  }
550
551  return Sum;
552}
553
554bool BranchProbabilityInfo::
555isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const {
556  // Hot probability is at least 4/5 = 80%
557  // FIXME: Compare against a static "hot" BranchProbability.
558  return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
559}
560
561BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const {
562  uint32_t Sum = 0;
563  uint32_t MaxWeight = 0;
564  BasicBlock *MaxSucc = nullptr;
565
566  for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
567    BasicBlock *Succ = *I;
568    uint32_t Weight = getEdgeWeight(BB, Succ);
569    uint32_t PrevSum = Sum;
570
571    Sum += Weight;
572    assert(Sum > PrevSum); (void) PrevSum;
573
574    if (Weight > MaxWeight) {
575      MaxWeight = Weight;
576      MaxSucc = Succ;
577    }
578  }
579
580  // Hot probability is at least 4/5 = 80%
581  if (BranchProbability(MaxWeight, Sum) > BranchProbability(4, 5))
582    return MaxSucc;
583
584  return nullptr;
585}
586
587/// Get the raw edge weight for the edge. If can't find it, return
588/// DEFAULT_WEIGHT value. Here an edge is specified using PredBlock and an index
589/// to the successors.
590uint32_t BranchProbabilityInfo::
591getEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors) const {
592  DenseMap<Edge, uint32_t>::const_iterator I =
593      Weights.find(std::make_pair(Src, IndexInSuccessors));
594
595  if (I != Weights.end())
596    return I->second;
597
598  return DEFAULT_WEIGHT;
599}
600
601uint32_t BranchProbabilityInfo::getEdgeWeight(const BasicBlock *Src,
602                                              succ_const_iterator Dst) const {
603  return getEdgeWeight(Src, Dst.getSuccessorIndex());
604}
605
606/// Get the raw edge weight calculated for the block pair. This returns the sum
607/// of all raw edge weights from Src to Dst.
608uint32_t BranchProbabilityInfo::
609getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const {
610  uint32_t Weight = 0;
611  DenseMap<Edge, uint32_t>::const_iterator MapI;
612  for (succ_const_iterator I = succ_begin(Src), E = succ_end(Src); I != E; ++I)
613    if (*I == Dst) {
614      MapI = Weights.find(std::make_pair(Src, I.getSuccessorIndex()));
615      if (MapI != Weights.end())
616        Weight += MapI->second;
617    }
618  return (Weight == 0) ? DEFAULT_WEIGHT : Weight;
619}
620
621/// Set the edge weight for a given edge specified by PredBlock and an index
622/// to the successors.
623void BranchProbabilityInfo::
624setEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors,
625              uint32_t Weight) {
626  Weights[std::make_pair(Src, IndexInSuccessors)] = Weight;
627  DEBUG(dbgs() << "set edge " << Src->getName() << " -> "
628               << IndexInSuccessors << " successor weight to "
629               << Weight << "\n");
630}
631
632/// Get an edge's probability, relative to other out-edges from Src.
633BranchProbability BranchProbabilityInfo::
634getEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors) const {
635  uint32_t N = getEdgeWeight(Src, IndexInSuccessors);
636  uint32_t D = getSumForBlock(Src);
637
638  return BranchProbability(N, D);
639}
640
641/// Get the probability of going from Src to Dst. It returns the sum of all
642/// probabilities for edges from Src to Dst.
643BranchProbability BranchProbabilityInfo::
644getEdgeProbability(const BasicBlock *Src, const BasicBlock *Dst) const {
645
646  uint32_t N = getEdgeWeight(Src, Dst);
647  uint32_t D = getSumForBlock(Src);
648
649  return BranchProbability(N, D);
650}
651
652raw_ostream &
653BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
654                                            const BasicBlock *Src,
655                                            const BasicBlock *Dst) const {
656
657  const BranchProbability Prob = getEdgeProbability(Src, Dst);
658  OS << "edge " << Src->getName() << " -> " << Dst->getName()
659     << " probability is " << Prob
660     << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
661
662  return OS;
663}
664