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1 //===-- DifferenceEngine.cpp - Structural function/module comparison ------===//
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 // This header defines the implementation of the LLVM difference
11 // engine, which structurally compares global values within a module.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "DifferenceEngine.h"
16 
17 #include "llvm/Constants.h"
18 #include "llvm/Function.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Module.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/DenseSet.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/StringRef.h"
25 #include "llvm/ADT/StringSet.h"
26 #include "llvm/Support/CallSite.h"
27 #include "llvm/Support/CFG.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/Support/type_traits.h"
31 
32 #include <utility>
33 
34 using namespace llvm;
35 
36 namespace {
37 
38 /// A priority queue, implemented as a heap.
39 template <class T, class Sorter, unsigned InlineCapacity>
40 class PriorityQueue {
41   Sorter Precedes;
42   llvm::SmallVector<T, InlineCapacity> Storage;
43 
44 public:
PriorityQueue(const Sorter & Precedes)45   PriorityQueue(const Sorter &Precedes) : Precedes(Precedes) {}
46 
47   /// Checks whether the heap is empty.
empty() const48   bool empty() const { return Storage.empty(); }
49 
50   /// Insert a new value on the heap.
insert(const T & V)51   void insert(const T &V) {
52     unsigned Index = Storage.size();
53     Storage.push_back(V);
54     if (Index == 0) return;
55 
56     T *data = Storage.data();
57     while (true) {
58       unsigned Target = (Index + 1) / 2 - 1;
59       if (!Precedes(data[Index], data[Target])) return;
60       std::swap(data[Index], data[Target]);
61       if (Target == 0) return;
62       Index = Target;
63     }
64   }
65 
66   /// Remove the minimum value in the heap.  Only valid on a non-empty heap.
remove_min()67   T remove_min() {
68     assert(!empty());
69     T tmp = Storage[0];
70 
71     unsigned NewSize = Storage.size() - 1;
72     if (NewSize) {
73       // Move the slot at the end to the beginning.
74       if (isPodLike<T>::value)
75         Storage[0] = Storage[NewSize];
76       else
77         std::swap(Storage[0], Storage[NewSize]);
78 
79       // Bubble the root up as necessary.
80       unsigned Index = 0;
81       while (true) {
82         // With a 1-based index, the children would be Index*2 and Index*2+1.
83         unsigned R = (Index + 1) * 2;
84         unsigned L = R - 1;
85 
86         // If R is out of bounds, we're done after this in any case.
87         if (R >= NewSize) {
88           // If L is also out of bounds, we're done immediately.
89           if (L >= NewSize) break;
90 
91           // Otherwise, test whether we should swap L and Index.
92           if (Precedes(Storage[L], Storage[Index]))
93             std::swap(Storage[L], Storage[Index]);
94           break;
95         }
96 
97         // Otherwise, we need to compare with the smaller of L and R.
98         // Prefer R because it's closer to the end of the array.
99         unsigned IndexToTest = (Precedes(Storage[L], Storage[R]) ? L : R);
100 
101         // If Index is >= the min of L and R, then heap ordering is restored.
102         if (!Precedes(Storage[IndexToTest], Storage[Index]))
103           break;
104 
105         // Otherwise, keep bubbling up.
106         std::swap(Storage[IndexToTest], Storage[Index]);
107         Index = IndexToTest;
108       }
109     }
110     Storage.pop_back();
111 
112     return tmp;
113   }
114 };
115 
116 /// A function-scope difference engine.
117 class FunctionDifferenceEngine {
118   DifferenceEngine &Engine;
119 
120   /// The current mapping from old local values to new local values.
121   DenseMap<Value*, Value*> Values;
122 
123   /// The current mapping from old blocks to new blocks.
124   DenseMap<BasicBlock*, BasicBlock*> Blocks;
125 
126   DenseSet<std::pair<Value*, Value*> > TentativeValues;
127 
getUnprocPredCount(BasicBlock * Block) const128   unsigned getUnprocPredCount(BasicBlock *Block) const {
129     unsigned Count = 0;
130     for (pred_iterator I = pred_begin(Block), E = pred_end(Block); I != E; ++I)
131       if (!Blocks.count(*I)) Count++;
132     return Count;
133   }
134 
135   typedef std::pair<BasicBlock*, BasicBlock*> BlockPair;
136 
137   /// A type which sorts a priority queue by the number of unprocessed
138   /// predecessor blocks it has remaining.
139   ///
140   /// This is actually really expensive to calculate.
141   struct QueueSorter {
142     const FunctionDifferenceEngine &fde;
QueueSorter__anonce6149d20111::FunctionDifferenceEngine::QueueSorter143     explicit QueueSorter(const FunctionDifferenceEngine &fde) : fde(fde) {}
144 
operator ()__anonce6149d20111::FunctionDifferenceEngine::QueueSorter145     bool operator()(const BlockPair &Old, const BlockPair &New) {
146       return fde.getUnprocPredCount(Old.first)
147            < fde.getUnprocPredCount(New.first);
148     }
149   };
150 
151   /// A queue of unified blocks to process.
152   PriorityQueue<BlockPair, QueueSorter, 20> Queue;
153 
154   /// Try to unify the given two blocks.  Enqueues them for processing
155   /// if they haven't already been processed.
156   ///
157   /// Returns true if there was a problem unifying them.
tryUnify(BasicBlock * L,BasicBlock * R)158   bool tryUnify(BasicBlock *L, BasicBlock *R) {
159     BasicBlock *&Ref = Blocks[L];
160 
161     if (Ref) {
162       if (Ref == R) return false;
163 
164       Engine.logf("successor %l cannot be equivalent to %r; "
165                   "it's already equivalent to %r")
166         << L << R << Ref;
167       return true;
168     }
169 
170     Ref = R;
171     Queue.insert(BlockPair(L, R));
172     return false;
173   }
174 
175   /// Unifies two instructions, given that they're known not to have
176   /// structural differences.
unify(Instruction * L,Instruction * R)177   void unify(Instruction *L, Instruction *R) {
178     DifferenceEngine::Context C(Engine, L, R);
179 
180     bool Result = diff(L, R, true, true);
181     assert(!Result && "structural differences second time around?");
182     (void) Result;
183     if (!L->use_empty())
184       Values[L] = R;
185   }
186 
processQueue()187   void processQueue() {
188     while (!Queue.empty()) {
189       BlockPair Pair = Queue.remove_min();
190       diff(Pair.first, Pair.second);
191     }
192   }
193 
diff(BasicBlock * L,BasicBlock * R)194   void diff(BasicBlock *L, BasicBlock *R) {
195     DifferenceEngine::Context C(Engine, L, R);
196 
197     BasicBlock::iterator LI = L->begin(), LE = L->end();
198     BasicBlock::iterator RI = R->begin();
199 
200     llvm::SmallVector<std::pair<Instruction*,Instruction*>, 20> TentativePairs;
201 
202     do {
203       assert(LI != LE && RI != R->end());
204       Instruction *LeftI = &*LI, *RightI = &*RI;
205 
206       // If the instructions differ, start the more sophisticated diff
207       // algorithm at the start of the block.
208       if (diff(LeftI, RightI, false, false)) {
209         TentativeValues.clear();
210         return runBlockDiff(L->begin(), R->begin());
211       }
212 
213       // Otherwise, tentatively unify them.
214       if (!LeftI->use_empty())
215         TentativeValues.insert(std::make_pair(LeftI, RightI));
216 
217       ++LI, ++RI;
218     } while (LI != LE); // This is sufficient: we can't get equality of
219                         // terminators if there are residual instructions.
220 
221     // Unify everything in the block, non-tentatively this time.
222     TentativeValues.clear();
223     for (LI = L->begin(), RI = R->begin(); LI != LE; ++LI, ++RI)
224       unify(&*LI, &*RI);
225   }
226 
227   bool matchForBlockDiff(Instruction *L, Instruction *R);
228   void runBlockDiff(BasicBlock::iterator LI, BasicBlock::iterator RI);
229 
diffCallSites(CallSite L,CallSite R,bool Complain)230   bool diffCallSites(CallSite L, CallSite R, bool Complain) {
231     // FIXME: call attributes
232     if (!equivalentAsOperands(L.getCalledValue(), R.getCalledValue())) {
233       if (Complain) Engine.log("called functions differ");
234       return true;
235     }
236     if (L.arg_size() != R.arg_size()) {
237       if (Complain) Engine.log("argument counts differ");
238       return true;
239     }
240     for (unsigned I = 0, E = L.arg_size(); I != E; ++I)
241       if (!equivalentAsOperands(L.getArgument(I), R.getArgument(I))) {
242         if (Complain)
243           Engine.logf("arguments %l and %r differ")
244             << L.getArgument(I) << R.getArgument(I);
245         return true;
246       }
247     return false;
248   }
249 
diff(Instruction * L,Instruction * R,bool Complain,bool TryUnify)250   bool diff(Instruction *L, Instruction *R, bool Complain, bool TryUnify) {
251     // FIXME: metadata (if Complain is set)
252 
253     // Different opcodes always imply different operations.
254     if (L->getOpcode() != R->getOpcode()) {
255       if (Complain) Engine.log("different instruction types");
256       return true;
257     }
258 
259     if (isa<CmpInst>(L)) {
260       if (cast<CmpInst>(L)->getPredicate()
261             != cast<CmpInst>(R)->getPredicate()) {
262         if (Complain) Engine.log("different predicates");
263         return true;
264       }
265     } else if (isa<CallInst>(L)) {
266       return diffCallSites(CallSite(L), CallSite(R), Complain);
267     } else if (isa<PHINode>(L)) {
268       // FIXME: implement.
269 
270       // This is really weird;  type uniquing is broken?
271       if (L->getType() != R->getType()) {
272         if (!L->getType()->isPointerTy() || !R->getType()->isPointerTy()) {
273           if (Complain) Engine.log("different phi types");
274           return true;
275         }
276       }
277       return false;
278 
279     // Terminators.
280     } else if (isa<InvokeInst>(L)) {
281       InvokeInst *LI = cast<InvokeInst>(L);
282       InvokeInst *RI = cast<InvokeInst>(R);
283       if (diffCallSites(CallSite(LI), CallSite(RI), Complain))
284         return true;
285 
286       if (TryUnify) {
287         tryUnify(LI->getNormalDest(), RI->getNormalDest());
288         tryUnify(LI->getUnwindDest(), RI->getUnwindDest());
289       }
290       return false;
291 
292     } else if (isa<BranchInst>(L)) {
293       BranchInst *LI = cast<BranchInst>(L);
294       BranchInst *RI = cast<BranchInst>(R);
295       if (LI->isConditional() != RI->isConditional()) {
296         if (Complain) Engine.log("branch conditionality differs");
297         return true;
298       }
299 
300       if (LI->isConditional()) {
301         if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
302           if (Complain) Engine.log("branch conditions differ");
303           return true;
304         }
305         if (TryUnify) tryUnify(LI->getSuccessor(1), RI->getSuccessor(1));
306       }
307       if (TryUnify) tryUnify(LI->getSuccessor(0), RI->getSuccessor(0));
308       return false;
309 
310     } else if (isa<SwitchInst>(L)) {
311       SwitchInst *LI = cast<SwitchInst>(L);
312       SwitchInst *RI = cast<SwitchInst>(R);
313       if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
314         if (Complain) Engine.log("switch conditions differ");
315         return true;
316       }
317       if (TryUnify) tryUnify(LI->getDefaultDest(), RI->getDefaultDest());
318 
319       bool Difference = false;
320 
321       DenseMap<ConstantInt*,BasicBlock*> LCases;
322       for (unsigned I = 1, E = LI->getNumCases(); I != E; ++I)
323         LCases[LI->getCaseValue(I)] = LI->getSuccessor(I);
324       for (unsigned I = 1, E = RI->getNumCases(); I != E; ++I) {
325         ConstantInt *CaseValue = RI->getCaseValue(I);
326         BasicBlock *LCase = LCases[CaseValue];
327         if (LCase) {
328           if (TryUnify) tryUnify(LCase, RI->getSuccessor(I));
329           LCases.erase(CaseValue);
330         } else if (!Difference) {
331           if (Complain)
332             Engine.logf("right switch has extra case %r") << CaseValue;
333           Difference = true;
334         }
335       }
336       if (!Difference)
337         for (DenseMap<ConstantInt*,BasicBlock*>::iterator
338                I = LCases.begin(), E = LCases.end(); I != E; ++I) {
339           if (Complain)
340             Engine.logf("left switch has extra case %l") << I->first;
341           Difference = true;
342         }
343       return Difference;
344     } else if (isa<UnreachableInst>(L)) {
345       return false;
346     }
347 
348     if (L->getNumOperands() != R->getNumOperands()) {
349       if (Complain) Engine.log("instructions have different operand counts");
350       return true;
351     }
352 
353     for (unsigned I = 0, E = L->getNumOperands(); I != E; ++I) {
354       Value *LO = L->getOperand(I), *RO = R->getOperand(I);
355       if (!equivalentAsOperands(LO, RO)) {
356         if (Complain) Engine.logf("operands %l and %r differ") << LO << RO;
357         return true;
358       }
359     }
360 
361     return false;
362   }
363 
equivalentAsOperands(Constant * L,Constant * R)364   bool equivalentAsOperands(Constant *L, Constant *R) {
365     // Use equality as a preliminary filter.
366     if (L == R)
367       return true;
368 
369     if (L->getValueID() != R->getValueID())
370       return false;
371 
372     // Ask the engine about global values.
373     if (isa<GlobalValue>(L))
374       return Engine.equivalentAsOperands(cast<GlobalValue>(L),
375                                          cast<GlobalValue>(R));
376 
377     // Compare constant expressions structurally.
378     if (isa<ConstantExpr>(L))
379       return equivalentAsOperands(cast<ConstantExpr>(L),
380                                   cast<ConstantExpr>(R));
381 
382     // Nulls of the "same type" don't always actually have the same
383     // type; I don't know why.  Just white-list them.
384     if (isa<ConstantPointerNull>(L))
385       return true;
386 
387     // Block addresses only match if we've already encountered the
388     // block.  FIXME: tentative matches?
389     if (isa<BlockAddress>(L))
390       return Blocks[cast<BlockAddress>(L)->getBasicBlock()]
391                  == cast<BlockAddress>(R)->getBasicBlock();
392 
393     return false;
394   }
395 
equivalentAsOperands(ConstantExpr * L,ConstantExpr * R)396   bool equivalentAsOperands(ConstantExpr *L, ConstantExpr *R) {
397     if (L == R)
398       return true;
399     if (L->getOpcode() != R->getOpcode())
400       return false;
401 
402     switch (L->getOpcode()) {
403     case Instruction::ICmp:
404     case Instruction::FCmp:
405       if (L->getPredicate() != R->getPredicate())
406         return false;
407       break;
408 
409     case Instruction::GetElementPtr:
410       // FIXME: inbounds?
411       break;
412 
413     default:
414       break;
415     }
416 
417     if (L->getNumOperands() != R->getNumOperands())
418       return false;
419 
420     for (unsigned I = 0, E = L->getNumOperands(); I != E; ++I)
421       if (!equivalentAsOperands(L->getOperand(I), R->getOperand(I)))
422         return false;
423 
424     return true;
425   }
426 
equivalentAsOperands(Value * L,Value * R)427   bool equivalentAsOperands(Value *L, Value *R) {
428     // Fall out if the values have different kind.
429     // This possibly shouldn't take priority over oracles.
430     if (L->getValueID() != R->getValueID())
431       return false;
432 
433     // Value subtypes:  Argument, Constant, Instruction, BasicBlock,
434     //                  InlineAsm, MDNode, MDString, PseudoSourceValue
435 
436     if (isa<Constant>(L))
437       return equivalentAsOperands(cast<Constant>(L), cast<Constant>(R));
438 
439     if (isa<Instruction>(L))
440       return Values[L] == R || TentativeValues.count(std::make_pair(L, R));
441 
442     if (isa<Argument>(L))
443       return Values[L] == R;
444 
445     if (isa<BasicBlock>(L))
446       return Blocks[cast<BasicBlock>(L)] != R;
447 
448     // Pretend everything else is identical.
449     return true;
450   }
451 
452   // Avoid a gcc warning about accessing 'this' in an initializer.
this_()453   FunctionDifferenceEngine *this_() { return this; }
454 
455 public:
FunctionDifferenceEngine(DifferenceEngine & Engine)456   FunctionDifferenceEngine(DifferenceEngine &Engine) :
457     Engine(Engine), Queue(QueueSorter(*this_())) {}
458 
diff(Function * L,Function * R)459   void diff(Function *L, Function *R) {
460     if (L->arg_size() != R->arg_size())
461       Engine.log("different argument counts");
462 
463     // Map the arguments.
464     for (Function::arg_iterator
465            LI = L->arg_begin(), LE = L->arg_end(),
466            RI = R->arg_begin(), RE = R->arg_end();
467          LI != LE && RI != RE; ++LI, ++RI)
468       Values[&*LI] = &*RI;
469 
470     tryUnify(&*L->begin(), &*R->begin());
471     processQueue();
472   }
473 };
474 
475 struct DiffEntry {
DiffEntry__anonce6149d20111::DiffEntry476   DiffEntry() : Cost(0) {}
477 
478   unsigned Cost;
479   llvm::SmallVector<char, 8> Path; // actually of DifferenceEngine::DiffChange
480 };
481 
matchForBlockDiff(Instruction * L,Instruction * R)482 bool FunctionDifferenceEngine::matchForBlockDiff(Instruction *L,
483                                                  Instruction *R) {
484   return !diff(L, R, false, false);
485 }
486 
runBlockDiff(BasicBlock::iterator LStart,BasicBlock::iterator RStart)487 void FunctionDifferenceEngine::runBlockDiff(BasicBlock::iterator LStart,
488                                             BasicBlock::iterator RStart) {
489   BasicBlock::iterator LE = LStart->getParent()->end();
490   BasicBlock::iterator RE = RStart->getParent()->end();
491 
492   unsigned NL = std::distance(LStart, LE);
493 
494   SmallVector<DiffEntry, 20> Paths1(NL+1);
495   SmallVector<DiffEntry, 20> Paths2(NL+1);
496 
497   DiffEntry *Cur = Paths1.data();
498   DiffEntry *Next = Paths2.data();
499 
500   const unsigned LeftCost = 2;
501   const unsigned RightCost = 2;
502   const unsigned MatchCost = 0;
503 
504   assert(TentativeValues.empty());
505 
506   // Initialize the first column.
507   for (unsigned I = 0; I != NL+1; ++I) {
508     Cur[I].Cost = I * LeftCost;
509     for (unsigned J = 0; J != I; ++J)
510       Cur[I].Path.push_back(DC_left);
511   }
512 
513   for (BasicBlock::iterator RI = RStart; RI != RE; ++RI) {
514     // Initialize the first row.
515     Next[0] = Cur[0];
516     Next[0].Cost += RightCost;
517     Next[0].Path.push_back(DC_right);
518 
519     unsigned Index = 1;
520     for (BasicBlock::iterator LI = LStart; LI != LE; ++LI, ++Index) {
521       if (matchForBlockDiff(&*LI, &*RI)) {
522         Next[Index] = Cur[Index-1];
523         Next[Index].Cost += MatchCost;
524         Next[Index].Path.push_back(DC_match);
525         TentativeValues.insert(std::make_pair(&*LI, &*RI));
526       } else if (Next[Index-1].Cost <= Cur[Index].Cost) {
527         Next[Index] = Next[Index-1];
528         Next[Index].Cost += LeftCost;
529         Next[Index].Path.push_back(DC_left);
530       } else {
531         Next[Index] = Cur[Index];
532         Next[Index].Cost += RightCost;
533         Next[Index].Path.push_back(DC_right);
534       }
535     }
536 
537     std::swap(Cur, Next);
538   }
539 
540   // We don't need the tentative values anymore; everything from here
541   // on out should be non-tentative.
542   TentativeValues.clear();
543 
544   SmallVectorImpl<char> &Path = Cur[NL].Path;
545   BasicBlock::iterator LI = LStart, RI = RStart;
546 
547   DiffLogBuilder Diff(Engine.getConsumer());
548 
549   // Drop trailing matches.
550   while (Path.back() == DC_match)
551     Path.pop_back();
552 
553   // Skip leading matches.
554   SmallVectorImpl<char>::iterator
555     PI = Path.begin(), PE = Path.end();
556   while (PI != PE && *PI == DC_match) {
557     unify(&*LI, &*RI);
558     ++PI, ++LI, ++RI;
559   }
560 
561   for (; PI != PE; ++PI) {
562     switch (static_cast<DiffChange>(*PI)) {
563     case DC_match:
564       assert(LI != LE && RI != RE);
565       {
566         Instruction *L = &*LI, *R = &*RI;
567         unify(L, R);
568         Diff.addMatch(L, R);
569       }
570       ++LI; ++RI;
571       break;
572 
573     case DC_left:
574       assert(LI != LE);
575       Diff.addLeft(&*LI);
576       ++LI;
577       break;
578 
579     case DC_right:
580       assert(RI != RE);
581       Diff.addRight(&*RI);
582       ++RI;
583       break;
584     }
585   }
586 
587   // Finishing unifying and complaining about the tails of the block,
588   // which should be matches all the way through.
589   while (LI != LE) {
590     assert(RI != RE);
591     unify(&*LI, &*RI);
592     ++LI, ++RI;
593   }
594 
595   // If the terminators have different kinds, but one is an invoke and the
596   // other is an unconditional branch immediately following a call, unify
597   // the results and the destinations.
598   TerminatorInst *LTerm = LStart->getParent()->getTerminator();
599   TerminatorInst *RTerm = RStart->getParent()->getTerminator();
600   if (isa<BranchInst>(LTerm) && isa<InvokeInst>(RTerm)) {
601     if (cast<BranchInst>(LTerm)->isConditional()) return;
602     BasicBlock::iterator I = LTerm;
603     if (I == LStart->getParent()->begin()) return;
604     --I;
605     if (!isa<CallInst>(*I)) return;
606     CallInst *LCall = cast<CallInst>(&*I);
607     InvokeInst *RInvoke = cast<InvokeInst>(RTerm);
608     if (!equivalentAsOperands(LCall->getCalledValue(), RInvoke->getCalledValue()))
609       return;
610     if (!LCall->use_empty())
611       Values[LCall] = RInvoke;
612     tryUnify(LTerm->getSuccessor(0), RInvoke->getNormalDest());
613   } else if (isa<InvokeInst>(LTerm) && isa<BranchInst>(RTerm)) {
614     if (cast<BranchInst>(RTerm)->isConditional()) return;
615     BasicBlock::iterator I = RTerm;
616     if (I == RStart->getParent()->begin()) return;
617     --I;
618     if (!isa<CallInst>(*I)) return;
619     CallInst *RCall = cast<CallInst>(I);
620     InvokeInst *LInvoke = cast<InvokeInst>(LTerm);
621     if (!equivalentAsOperands(LInvoke->getCalledValue(), RCall->getCalledValue()))
622       return;
623     if (!LInvoke->use_empty())
624       Values[LInvoke] = RCall;
625     tryUnify(LInvoke->getNormalDest(), RTerm->getSuccessor(0));
626   }
627 }
628 
629 }
630 
diff(Function * L,Function * R)631 void DifferenceEngine::diff(Function *L, Function *R) {
632   Context C(*this, L, R);
633 
634   // FIXME: types
635   // FIXME: attributes and CC
636   // FIXME: parameter attributes
637 
638   // If both are declarations, we're done.
639   if (L->empty() && R->empty())
640     return;
641   else if (L->empty())
642     log("left function is declaration, right function is definition");
643   else if (R->empty())
644     log("right function is declaration, left function is definition");
645   else
646     FunctionDifferenceEngine(*this).diff(L, R);
647 }
648 
diff(Module * L,Module * R)649 void DifferenceEngine::diff(Module *L, Module *R) {
650   StringSet<> LNames;
651   SmallVector<std::pair<Function*,Function*>, 20> Queue;
652 
653   for (Module::iterator I = L->begin(), E = L->end(); I != E; ++I) {
654     Function *LFn = &*I;
655     LNames.insert(LFn->getName());
656 
657     if (Function *RFn = R->getFunction(LFn->getName()))
658       Queue.push_back(std::make_pair(LFn, RFn));
659     else
660       logf("function %l exists only in left module") << LFn;
661   }
662 
663   for (Module::iterator I = R->begin(), E = R->end(); I != E; ++I) {
664     Function *RFn = &*I;
665     if (!LNames.count(RFn->getName()))
666       logf("function %r exists only in right module") << RFn;
667   }
668 
669   for (SmallVectorImpl<std::pair<Function*,Function*> >::iterator
670          I = Queue.begin(), E = Queue.end(); I != E; ++I)
671     diff(I->first, I->second);
672 }
673 
equivalentAsOperands(GlobalValue * L,GlobalValue * R)674 bool DifferenceEngine::equivalentAsOperands(GlobalValue *L, GlobalValue *R) {
675   if (globalValueOracle) return (*globalValueOracle)(L, R);
676   return L->getName() == R->getName();
677 }
678