1 //===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Loops should be simplified before this analysis.
12 //===----------------------------------------------------------------------===//
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 #include "llvm/Support/raw_ostream.h"
28 #define DEBUG_TYPE "branch-prob"
30 INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
31 "Branch Probability Analysis", false, true)
32 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
33 INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
34 "Branch Probability Analysis", false, true)
36 char BranchProbabilityInfoWrapperPass::ID = 0;
38 // Weights are for internal use only. They are used by heuristics to help to
39 // estimate edges' probability. Example:
41 // Using "Loop Branch Heuristics" we predict weights of edges for the
56 // Probability of the edge BB2->BB1 = 124 / (124 + 4) = 0.96875
57 // Probability of the edge BB2->BB3 = 4 / (124 + 4) = 0.03125
58 static const uint32_t LBH_TAKEN_WEIGHT = 124;
59 static const uint32_t LBH_NONTAKEN_WEIGHT = 4;
61 /// \brief Unreachable-terminating branch taken weight.
63 /// This is the weight for a branch being taken to a block that terminates
64 /// (eventually) in unreachable. These are predicted as unlikely as possible.
65 static const uint32_t UR_TAKEN_WEIGHT = 1;
67 /// \brief Unreachable-terminating branch not-taken weight.
69 /// This is the weight for a branch not being taken toward a block that
70 /// terminates (eventually) in unreachable. Such a branch is essentially never
71 /// taken. Set the weight to an absurdly high value so that nested loops don't
72 /// easily subsume it.
73 static const uint32_t UR_NONTAKEN_WEIGHT = 1024*1024 - 1;
75 /// \brief Weight for a branch taken going into a cold block.
77 /// This is the weight for a branch taken toward a block marked
78 /// cold. A block is marked cold if it's postdominated by a
79 /// block containing a call to a cold function. Cold functions
80 /// are those marked with attribute 'cold'.
81 static const uint32_t CC_TAKEN_WEIGHT = 4;
83 /// \brief Weight for a branch not-taken into a cold block.
85 /// This is the weight for a branch not taken toward a block marked
87 static const uint32_t CC_NONTAKEN_WEIGHT = 64;
89 static const uint32_t PH_TAKEN_WEIGHT = 20;
90 static const uint32_t PH_NONTAKEN_WEIGHT = 12;
92 static const uint32_t ZH_TAKEN_WEIGHT = 20;
93 static const uint32_t ZH_NONTAKEN_WEIGHT = 12;
95 static const uint32_t FPH_TAKEN_WEIGHT = 20;
96 static const uint32_t FPH_NONTAKEN_WEIGHT = 12;
98 /// \brief Invoke-terminating normal branch taken weight
100 /// This is the weight for branching to the normal destination of an invoke
101 /// instruction. We expect this to happen most of the time. Set the weight to an
102 /// absurdly high value so that nested loops subsume it.
103 static const uint32_t IH_TAKEN_WEIGHT = 1024 * 1024 - 1;
105 /// \brief Invoke-terminating normal branch not-taken weight.
107 /// This is the weight for branching to the unwind destination of an invoke
108 /// instruction. This is essentially never taken.
109 static const uint32_t IH_NONTAKEN_WEIGHT = 1;
111 /// \brief Calculate edge weights for successors lead to unreachable.
113 /// Predict that a successor which leads necessarily to an
114 /// unreachable-terminated block as extremely unlikely.
115 bool BranchProbabilityInfo::calcUnreachableHeuristics(BasicBlock *BB) {
116 TerminatorInst *TI = BB->getTerminator();
117 if (TI->getNumSuccessors() == 0) {
118 if (isa<UnreachableInst>(TI))
119 PostDominatedByUnreachable.insert(BB);
123 SmallVector<unsigned, 4> UnreachableEdges;
124 SmallVector<unsigned, 4> ReachableEdges;
126 for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
127 if (PostDominatedByUnreachable.count(*I))
128 UnreachableEdges.push_back(I.getSuccessorIndex());
130 ReachableEdges.push_back(I.getSuccessorIndex());
133 // If all successors are in the set of blocks post-dominated by unreachable,
134 // this block is too.
135 if (UnreachableEdges.size() == TI->getNumSuccessors())
136 PostDominatedByUnreachable.insert(BB);
138 // Skip probabilities if this block has a single successor or if all were
140 if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
143 // If the terminator is an InvokeInst, check only the normal destination block
144 // as the unwind edge of InvokeInst is also very unlikely taken.
145 if (auto *II = dyn_cast<InvokeInst>(TI))
146 if (PostDominatedByUnreachable.count(II->getNormalDest())) {
147 PostDominatedByUnreachable.insert(BB);
148 // Return false here so that edge weights for InvokeInst could be decided
149 // in calcInvokeHeuristics().
153 if (ReachableEdges.empty()) {
154 BranchProbability Prob(1, UnreachableEdges.size());
155 for (unsigned SuccIdx : UnreachableEdges)
156 setEdgeProbability(BB, SuccIdx, Prob);
160 BranchProbability UnreachableProb(UR_TAKEN_WEIGHT,
161 (UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
162 UnreachableEdges.size());
163 BranchProbability ReachableProb(UR_NONTAKEN_WEIGHT,
164 (UR_TAKEN_WEIGHT + UR_NONTAKEN_WEIGHT) *
165 ReachableEdges.size());
167 for (unsigned SuccIdx : UnreachableEdges)
168 setEdgeProbability(BB, SuccIdx, UnreachableProb);
169 for (unsigned SuccIdx : ReachableEdges)
170 setEdgeProbability(BB, SuccIdx, ReachableProb);
175 // Propagate existing explicit probabilities from either profile data or
176 // 'expect' intrinsic processing.
177 bool BranchProbabilityInfo::calcMetadataWeights(BasicBlock *BB) {
178 TerminatorInst *TI = BB->getTerminator();
179 if (TI->getNumSuccessors() == 1)
181 if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
184 MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
188 // Check that the number of successors is manageable.
189 assert(TI->getNumSuccessors() < UINT32_MAX && "Too many successors");
191 // Ensure there are weights for all of the successors. Note that the first
192 // operand to the metadata node is a name, not a weight.
193 if (WeightsNode->getNumOperands() != TI->getNumSuccessors() + 1)
196 // Build up the final weights that will be used in a temporary buffer.
197 // Compute the sum of all weights to later decide whether they need to
198 // be scaled to fit in 32 bits.
199 uint64_t WeightSum = 0;
200 SmallVector<uint32_t, 2> Weights;
201 Weights.reserve(TI->getNumSuccessors());
202 for (unsigned i = 1, e = WeightsNode->getNumOperands(); i != e; ++i) {
203 ConstantInt *Weight =
204 mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(i));
207 assert(Weight->getValue().getActiveBits() <= 32 &&
208 "Too many bits for uint32_t");
209 Weights.push_back(Weight->getZExtValue());
210 WeightSum += Weights.back();
212 assert(Weights.size() == TI->getNumSuccessors() && "Checked above");
214 // If the sum of weights does not fit in 32 bits, scale every weight down
216 uint64_t ScalingFactor =
217 (WeightSum > UINT32_MAX) ? WeightSum / UINT32_MAX + 1 : 1;
220 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
221 Weights[i] /= ScalingFactor;
222 WeightSum += Weights[i];
224 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
225 setEdgeProbability(BB, i, {Weights[i], static_cast<uint32_t>(WeightSum)});
227 assert(WeightSum <= UINT32_MAX &&
228 "Expected weights to scale down to 32 bits");
233 /// \brief Calculate edge weights for edges leading to cold blocks.
235 /// A cold block is one post-dominated by a block with a call to a
236 /// cold function. Those edges are unlikely to be taken, so we give
237 /// them relatively low weight.
239 /// Return true if we could compute the weights for cold edges.
240 /// Return false, otherwise.
241 bool BranchProbabilityInfo::calcColdCallHeuristics(BasicBlock *BB) {
242 TerminatorInst *TI = BB->getTerminator();
243 if (TI->getNumSuccessors() == 0)
246 // Determine which successors are post-dominated by a cold block.
247 SmallVector<unsigned, 4> ColdEdges;
248 SmallVector<unsigned, 4> NormalEdges;
249 for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I)
250 if (PostDominatedByColdCall.count(*I))
251 ColdEdges.push_back(I.getSuccessorIndex());
253 NormalEdges.push_back(I.getSuccessorIndex());
255 // If all successors are in the set of blocks post-dominated by cold calls,
256 // this block is in the set post-dominated by cold calls.
257 if (ColdEdges.size() == TI->getNumSuccessors())
258 PostDominatedByColdCall.insert(BB);
260 // Otherwise, if the block itself contains a cold function, add it to the
261 // set of blocks postdominated by a cold call.
262 assert(!PostDominatedByColdCall.count(BB));
263 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
264 if (CallInst *CI = dyn_cast<CallInst>(I))
265 if (CI->hasFnAttr(Attribute::Cold)) {
266 PostDominatedByColdCall.insert(BB);
271 // Skip probabilities if this block has a single successor.
272 if (TI->getNumSuccessors() == 1 || ColdEdges.empty())
275 if (NormalEdges.empty()) {
276 BranchProbability Prob(1, ColdEdges.size());
277 for (unsigned SuccIdx : ColdEdges)
278 setEdgeProbability(BB, SuccIdx, Prob);
282 BranchProbability ColdProb(CC_TAKEN_WEIGHT,
283 (CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
285 BranchProbability NormalProb(CC_NONTAKEN_WEIGHT,
286 (CC_TAKEN_WEIGHT + CC_NONTAKEN_WEIGHT) *
289 for (unsigned SuccIdx : ColdEdges)
290 setEdgeProbability(BB, SuccIdx, ColdProb);
291 for (unsigned SuccIdx : NormalEdges)
292 setEdgeProbability(BB, SuccIdx, NormalProb);
297 // Calculate Edge Weights using "Pointer Heuristics". Predict a comparsion
298 // between two pointer or pointer and NULL will fail.
299 bool BranchProbabilityInfo::calcPointerHeuristics(BasicBlock *BB) {
300 BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
301 if (!BI || !BI->isConditional())
304 Value *Cond = BI->getCondition();
305 ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
306 if (!CI || !CI->isEquality())
309 Value *LHS = CI->getOperand(0);
311 if (!LHS->getType()->isPointerTy())
314 assert(CI->getOperand(1)->getType()->isPointerTy());
316 // p != 0 -> isProb = true
317 // p == 0 -> isProb = false
318 // p != q -> isProb = true
319 // p == q -> isProb = false;
320 unsigned TakenIdx = 0, NonTakenIdx = 1;
321 bool isProb = CI->getPredicate() == ICmpInst::ICMP_NE;
323 std::swap(TakenIdx, NonTakenIdx);
325 BranchProbability TakenProb(PH_TAKEN_WEIGHT,
326 PH_TAKEN_WEIGHT + PH_NONTAKEN_WEIGHT);
327 setEdgeProbability(BB, TakenIdx, TakenProb);
328 setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
332 // Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
333 // as taken, exiting edges as not-taken.
334 bool BranchProbabilityInfo::calcLoopBranchHeuristics(BasicBlock *BB,
335 const LoopInfo &LI) {
336 Loop *L = LI.getLoopFor(BB);
340 SmallVector<unsigned, 8> BackEdges;
341 SmallVector<unsigned, 8> ExitingEdges;
342 SmallVector<unsigned, 8> InEdges; // Edges from header to the loop.
344 for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
345 if (!L->contains(*I))
346 ExitingEdges.push_back(I.getSuccessorIndex());
347 else if (L->getHeader() == *I)
348 BackEdges.push_back(I.getSuccessorIndex());
350 InEdges.push_back(I.getSuccessorIndex());
353 if (BackEdges.empty() && ExitingEdges.empty())
356 // Collect the sum of probabilities of back-edges/in-edges/exiting-edges, and
357 // normalize them so that they sum up to one.
358 SmallVector<BranchProbability, 4> Probs(3, BranchProbability::getZero());
359 unsigned Denom = (BackEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
360 (InEdges.empty() ? 0 : LBH_TAKEN_WEIGHT) +
361 (ExitingEdges.empty() ? 0 : LBH_NONTAKEN_WEIGHT);
362 if (!BackEdges.empty())
363 Probs[0] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
364 if (!InEdges.empty())
365 Probs[1] = BranchProbability(LBH_TAKEN_WEIGHT, Denom);
366 if (!ExitingEdges.empty())
367 Probs[2] = BranchProbability(LBH_NONTAKEN_WEIGHT, Denom);
369 if (uint32_t numBackEdges = BackEdges.size()) {
370 auto Prob = Probs[0] / numBackEdges;
371 for (unsigned SuccIdx : BackEdges)
372 setEdgeProbability(BB, SuccIdx, Prob);
375 if (uint32_t numInEdges = InEdges.size()) {
376 auto Prob = Probs[1] / numInEdges;
377 for (unsigned SuccIdx : InEdges)
378 setEdgeProbability(BB, SuccIdx, Prob);
381 if (uint32_t numExitingEdges = ExitingEdges.size()) {
382 auto Prob = Probs[2] / numExitingEdges;
383 for (unsigned SuccIdx : ExitingEdges)
384 setEdgeProbability(BB, SuccIdx, Prob);
390 bool BranchProbabilityInfo::calcZeroHeuristics(BasicBlock *BB) {
391 BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
392 if (!BI || !BI->isConditional())
395 Value *Cond = BI->getCondition();
396 ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
400 Value *RHS = CI->getOperand(1);
401 ConstantInt *CV = dyn_cast<ConstantInt>(RHS);
405 // If the LHS is the result of AND'ing a value with a single bit bitmask,
406 // we don't have information about probabilities.
407 if (Instruction *LHS = dyn_cast<Instruction>(CI->getOperand(0)))
408 if (LHS->getOpcode() == Instruction::And)
409 if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(LHS->getOperand(1)))
410 if (AndRHS->getUniqueInteger().isPowerOf2())
415 switch (CI->getPredicate()) {
416 case CmpInst::ICMP_EQ:
417 // X == 0 -> Unlikely
420 case CmpInst::ICMP_NE:
424 case CmpInst::ICMP_SLT:
428 case CmpInst::ICMP_SGT:
435 } else if (CV->isOne() && CI->getPredicate() == CmpInst::ICMP_SLT) {
436 // InstCombine canonicalizes X <= 0 into X < 1.
437 // X <= 0 -> Unlikely
439 } else if (CV->isAllOnesValue()) {
440 switch (CI->getPredicate()) {
441 case CmpInst::ICMP_EQ:
442 // X == -1 -> Unlikely
445 case CmpInst::ICMP_NE:
449 case CmpInst::ICMP_SGT:
450 // InstCombine canonicalizes X >= 0 into X > -1.
461 unsigned TakenIdx = 0, NonTakenIdx = 1;
464 std::swap(TakenIdx, NonTakenIdx);
466 BranchProbability TakenProb(ZH_TAKEN_WEIGHT,
467 ZH_TAKEN_WEIGHT + ZH_NONTAKEN_WEIGHT);
468 setEdgeProbability(BB, TakenIdx, TakenProb);
469 setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
473 bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) {
474 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
475 if (!BI || !BI->isConditional())
478 Value *Cond = BI->getCondition();
479 FCmpInst *FCmp = dyn_cast<FCmpInst>(Cond);
484 if (FCmp->isEquality()) {
485 // f1 == f2 -> Unlikely
486 // f1 != f2 -> Likely
487 isProb = !FCmp->isTrueWhenEqual();
488 } else if (FCmp->getPredicate() == FCmpInst::FCMP_ORD) {
491 } else if (FCmp->getPredicate() == FCmpInst::FCMP_UNO) {
498 unsigned TakenIdx = 0, NonTakenIdx = 1;
501 std::swap(TakenIdx, NonTakenIdx);
503 BranchProbability TakenProb(FPH_TAKEN_WEIGHT,
504 FPH_TAKEN_WEIGHT + FPH_NONTAKEN_WEIGHT);
505 setEdgeProbability(BB, TakenIdx, TakenProb);
506 setEdgeProbability(BB, NonTakenIdx, TakenProb.getCompl());
510 bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
511 InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator());
515 BranchProbability TakenProb(IH_TAKEN_WEIGHT,
516 IH_TAKEN_WEIGHT + IH_NONTAKEN_WEIGHT);
517 setEdgeProbability(BB, 0 /*Index for Normal*/, TakenProb);
518 setEdgeProbability(BB, 1 /*Index for Unwind*/, TakenProb.getCompl());
522 void BranchProbabilityInfo::releaseMemory() {
526 void BranchProbabilityInfo::print(raw_ostream &OS) 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 (const auto &BI : *LastF) {
532 for (succ_const_iterator SI = succ_begin(&BI), SE = succ_end(&BI); SI != SE;
534 printEdgeProbability(OS << " ", &BI, *SI);
539 bool BranchProbabilityInfo::
540 isEdgeHot(const BasicBlock *Src, const BasicBlock *Dst) const {
541 // Hot probability is at least 4/5 = 80%
542 // FIXME: Compare against a static "hot" BranchProbability.
543 return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
546 BasicBlock *BranchProbabilityInfo::getHotSucc(BasicBlock *BB) const {
547 auto MaxProb = BranchProbability::getZero();
548 BasicBlock *MaxSucc = nullptr;
550 for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
551 BasicBlock *Succ = *I;
552 auto Prob = getEdgeProbability(BB, Succ);
553 if (Prob > MaxProb) {
559 // Hot probability is at least 4/5 = 80%
560 if (MaxProb > BranchProbability(4, 5))
566 /// Get the raw edge probability for the edge. If can't find it, return a
567 /// default probability 1/N where N is the number of successors. Here an edge is
568 /// specified using PredBlock and an
569 /// index to the successors.
571 BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
572 unsigned IndexInSuccessors) const {
573 auto I = Probs.find(std::make_pair(Src, IndexInSuccessors));
575 if (I != Probs.end())
579 static_cast<uint32_t>(std::distance(succ_begin(Src), succ_end(Src)))};
583 BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
584 succ_const_iterator Dst) const {
585 return getEdgeProbability(Src, Dst.getSuccessorIndex());
588 /// Get the raw edge probability calculated for the block pair. This returns the
589 /// sum of all raw edge probabilities from Src to Dst.
591 BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
592 const BasicBlock *Dst) const {
593 auto Prob = BranchProbability::getZero();
594 bool FoundProb = false;
595 for (succ_const_iterator I = succ_begin(Src), E = succ_end(Src); I != E; ++I)
597 auto MapI = Probs.find(std::make_pair(Src, I.getSuccessorIndex()));
598 if (MapI != Probs.end()) {
600 Prob += MapI->second;
603 uint32_t succ_num = std::distance(succ_begin(Src), succ_end(Src));
604 return FoundProb ? Prob : BranchProbability(1, succ_num);
607 /// Set the edge probability for a given edge specified by PredBlock and an
608 /// index to the successors.
609 void BranchProbabilityInfo::setEdgeProbability(const BasicBlock *Src,
610 unsigned IndexInSuccessors,
611 BranchProbability Prob) {
612 Probs[std::make_pair(Src, IndexInSuccessors)] = Prob;
613 DEBUG(dbgs() << "set edge " << Src->getName() << " -> " << IndexInSuccessors
614 << " successor probability to " << Prob << "\n");
618 BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
619 const BasicBlock *Src,
620 const BasicBlock *Dst) const {
622 const BranchProbability Prob = getEdgeProbability(Src, Dst);
623 OS << "edge " << Src->getName() << " -> " << Dst->getName()
624 << " probability is " << Prob
625 << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
630 void BranchProbabilityInfo::calculate(Function &F, const LoopInfo& LI) {
631 DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
633 LastF = &F; // Store the last function we ran on for printing.
634 assert(PostDominatedByUnreachable.empty());
635 assert(PostDominatedByColdCall.empty());
637 // Walk the basic blocks in post-order so that we can build up state about
638 // the successors of a block iteratively.
639 for (auto BB : post_order(&F.getEntryBlock())) {
640 DEBUG(dbgs() << "Computing probabilities for " << BB->getName() << "\n");
641 if (calcUnreachableHeuristics(BB))
643 if (calcMetadataWeights(BB))
645 if (calcColdCallHeuristics(BB))
647 if (calcLoopBranchHeuristics(BB, LI))
649 if (calcPointerHeuristics(BB))
651 if (calcZeroHeuristics(BB))
653 if (calcFloatingPointHeuristics(BB))
655 calcInvokeHeuristics(BB);
658 PostDominatedByUnreachable.clear();
659 PostDominatedByColdCall.clear();
662 void BranchProbabilityInfoWrapperPass::getAnalysisUsage(
663 AnalysisUsage &AU) const {
664 AU.addRequired<LoopInfoWrapperPass>();
665 AU.setPreservesAll();
668 bool BranchProbabilityInfoWrapperPass::runOnFunction(Function &F) {
669 const LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
670 BPI.calculate(F, LI);
674 void BranchProbabilityInfoWrapperPass::releaseMemory() { BPI.releaseMemory(); }
676 void BranchProbabilityInfoWrapperPass::print(raw_ostream &OS,
677 const Module *) const {