1 //===-- DifferenceEngine.cpp - Structural function/module comparison ------===//
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 // This header defines the implementation of the LLVM difference
11 // engine, which structurally compares global values within a module.
13 //===----------------------------------------------------------------------===//
15 #include "DifferenceEngine.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/DenseSet.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/StringSet.h"
21 #include "llvm/IR/CFG.h"
22 #include "llvm/IR/CallSite.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Support/type_traits.h"
36 /// A priority queue, implemented as a heap.
37 template <class T, class Sorter, unsigned InlineCapacity>
40 llvm::SmallVector<T, InlineCapacity> Storage;
43 PriorityQueue(const Sorter &Precedes) : Precedes(Precedes) {}
45 /// Checks whether the heap is empty.
46 bool empty() const { return Storage.empty(); }
48 /// Insert a new value on the heap.
49 void insert(const T &V) {
50 unsigned Index = Storage.size();
52 if (Index == 0) return;
54 T *data = Storage.data();
56 unsigned Target = (Index + 1) / 2 - 1;
57 if (!Precedes(data[Index], data[Target])) return;
58 std::swap(data[Index], data[Target]);
59 if (Target == 0) return;
64 /// Remove the minimum value in the heap. Only valid on a non-empty heap.
69 unsigned NewSize = Storage.size() - 1;
71 // Move the slot at the end to the beginning.
72 if (isPodLike<T>::value)
73 Storage[0] = Storage[NewSize];
75 std::swap(Storage[0], Storage[NewSize]);
77 // Bubble the root up as necessary.
80 // With a 1-based index, the children would be Index*2 and Index*2+1.
81 unsigned R = (Index + 1) * 2;
84 // If R is out of bounds, we're done after this in any case.
86 // If L is also out of bounds, we're done immediately.
87 if (L >= NewSize) break;
89 // Otherwise, test whether we should swap L and Index.
90 if (Precedes(Storage[L], Storage[Index]))
91 std::swap(Storage[L], Storage[Index]);
95 // Otherwise, we need to compare with the smaller of L and R.
96 // Prefer R because it's closer to the end of the array.
97 unsigned IndexToTest = (Precedes(Storage[L], Storage[R]) ? L : R);
99 // If Index is >= the min of L and R, then heap ordering is restored.
100 if (!Precedes(Storage[IndexToTest], Storage[Index]))
103 // Otherwise, keep bubbling up.
104 std::swap(Storage[IndexToTest], Storage[Index]);
114 /// A function-scope difference engine.
115 class FunctionDifferenceEngine {
116 DifferenceEngine &Engine;
118 /// The current mapping from old local values to new local values.
119 DenseMap<Value*, Value*> Values;
121 /// The current mapping from old blocks to new blocks.
122 DenseMap<BasicBlock*, BasicBlock*> Blocks;
124 DenseSet<std::pair<Value*, Value*> > TentativeValues;
126 unsigned getUnprocPredCount(BasicBlock *Block) const {
128 for (pred_iterator I = pred_begin(Block), E = pred_end(Block); I != E; ++I)
129 if (!Blocks.count(*I)) Count++;
133 typedef std::pair<BasicBlock*, BasicBlock*> BlockPair;
135 /// A type which sorts a priority queue by the number of unprocessed
136 /// predecessor blocks it has remaining.
138 /// This is actually really expensive to calculate.
140 const FunctionDifferenceEngine &fde;
141 explicit QueueSorter(const FunctionDifferenceEngine &fde) : fde(fde) {}
143 bool operator()(const BlockPair &Old, const BlockPair &New) {
144 return fde.getUnprocPredCount(Old.first)
145 < fde.getUnprocPredCount(New.first);
149 /// A queue of unified blocks to process.
150 PriorityQueue<BlockPair, QueueSorter, 20> Queue;
152 /// Try to unify the given two blocks. Enqueues them for processing
153 /// if they haven't already been processed.
155 /// Returns true if there was a problem unifying them.
156 bool tryUnify(BasicBlock *L, BasicBlock *R) {
157 BasicBlock *&Ref = Blocks[L];
160 if (Ref == R) return false;
162 Engine.logf("successor %l cannot be equivalent to %r; "
163 "it's already equivalent to %r")
169 Queue.insert(BlockPair(L, R));
173 /// Unifies two instructions, given that they're known not to have
174 /// structural differences.
175 void unify(Instruction *L, Instruction *R) {
176 DifferenceEngine::Context C(Engine, L, R);
178 bool Result = diff(L, R, true, true);
179 assert(!Result && "structural differences second time around?");
185 void processQueue() {
186 while (!Queue.empty()) {
187 BlockPair Pair = Queue.remove_min();
188 diff(Pair.first, Pair.second);
192 void diff(BasicBlock *L, BasicBlock *R) {
193 DifferenceEngine::Context C(Engine, L, R);
195 BasicBlock::iterator LI = L->begin(), LE = L->end();
196 BasicBlock::iterator RI = R->begin();
199 assert(LI != LE && RI != R->end());
200 Instruction *LeftI = &*LI, *RightI = &*RI;
202 // If the instructions differ, start the more sophisticated diff
203 // algorithm at the start of the block.
204 if (diff(LeftI, RightI, false, false)) {
205 TentativeValues.clear();
206 return runBlockDiff(L->begin(), R->begin());
209 // Otherwise, tentatively unify them.
210 if (!LeftI->use_empty())
211 TentativeValues.insert(std::make_pair(LeftI, RightI));
214 } while (LI != LE); // This is sufficient: we can't get equality of
215 // terminators if there are residual instructions.
217 // Unify everything in the block, non-tentatively this time.
218 TentativeValues.clear();
219 for (LI = L->begin(), RI = R->begin(); LI != LE; ++LI, ++RI)
223 bool matchForBlockDiff(Instruction *L, Instruction *R);
224 void runBlockDiff(BasicBlock::iterator LI, BasicBlock::iterator RI);
226 bool diffCallSites(CallSite L, CallSite R, bool Complain) {
227 // FIXME: call attributes
228 if (!equivalentAsOperands(L.getCalledValue(), R.getCalledValue())) {
229 if (Complain) Engine.log("called functions differ");
232 if (L.arg_size() != R.arg_size()) {
233 if (Complain) Engine.log("argument counts differ");
236 for (unsigned I = 0, E = L.arg_size(); I != E; ++I)
237 if (!equivalentAsOperands(L.getArgument(I), R.getArgument(I))) {
239 Engine.logf("arguments %l and %r differ")
240 << L.getArgument(I) << R.getArgument(I);
246 bool diff(Instruction *L, Instruction *R, bool Complain, bool TryUnify) {
247 // FIXME: metadata (if Complain is set)
249 // Different opcodes always imply different operations.
250 if (L->getOpcode() != R->getOpcode()) {
251 if (Complain) Engine.log("different instruction types");
255 if (isa<CmpInst>(L)) {
256 if (cast<CmpInst>(L)->getPredicate()
257 != cast<CmpInst>(R)->getPredicate()) {
258 if (Complain) Engine.log("different predicates");
261 } else if (isa<CallInst>(L)) {
262 return diffCallSites(CallSite(L), CallSite(R), Complain);
263 } else if (isa<PHINode>(L)) {
266 // This is really weird; type uniquing is broken?
267 if (L->getType() != R->getType()) {
268 if (!L->getType()->isPointerTy() || !R->getType()->isPointerTy()) {
269 if (Complain) Engine.log("different phi types");
276 } else if (isa<InvokeInst>(L)) {
277 InvokeInst *LI = cast<InvokeInst>(L);
278 InvokeInst *RI = cast<InvokeInst>(R);
279 if (diffCallSites(CallSite(LI), CallSite(RI), Complain))
283 tryUnify(LI->getNormalDest(), RI->getNormalDest());
284 tryUnify(LI->getUnwindDest(), RI->getUnwindDest());
288 } else if (isa<BranchInst>(L)) {
289 BranchInst *LI = cast<BranchInst>(L);
290 BranchInst *RI = cast<BranchInst>(R);
291 if (LI->isConditional() != RI->isConditional()) {
292 if (Complain) Engine.log("branch conditionality differs");
296 if (LI->isConditional()) {
297 if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
298 if (Complain) Engine.log("branch conditions differ");
301 if (TryUnify) tryUnify(LI->getSuccessor(1), RI->getSuccessor(1));
303 if (TryUnify) tryUnify(LI->getSuccessor(0), RI->getSuccessor(0));
306 } else if (isa<SwitchInst>(L)) {
307 SwitchInst *LI = cast<SwitchInst>(L);
308 SwitchInst *RI = cast<SwitchInst>(R);
309 if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
310 if (Complain) Engine.log("switch conditions differ");
313 if (TryUnify) tryUnify(LI->getDefaultDest(), RI->getDefaultDest());
315 bool Difference = false;
317 DenseMap<ConstantInt*,BasicBlock*> LCases;
319 for (SwitchInst::CaseIt I = LI->case_begin(), E = LI->case_end();
321 LCases[I.getCaseValue()] = I.getCaseSuccessor();
323 for (SwitchInst::CaseIt I = RI->case_begin(), E = RI->case_end();
325 ConstantInt *CaseValue = I.getCaseValue();
326 BasicBlock *LCase = LCases[CaseValue];
328 if (TryUnify) tryUnify(LCase, I.getCaseSuccessor());
329 LCases.erase(CaseValue);
330 } else if (Complain || !Difference) {
332 Engine.logf("right switch has extra case %r") << CaseValue;
337 for (DenseMap<ConstantInt*,BasicBlock*>::iterator
338 I = LCases.begin(), E = LCases.end(); I != E; ++I) {
340 Engine.logf("left switch has extra case %l") << I->first;
344 } else if (isa<UnreachableInst>(L)) {
348 if (L->getNumOperands() != R->getNumOperands()) {
349 if (Complain) Engine.log("instructions have different operand counts");
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;
364 bool equivalentAsOperands(Constant *L, Constant *R) {
365 // Use equality as a preliminary filter.
369 if (L->getValueID() != R->getValueID())
372 // Ask the engine about global values.
373 if (isa<GlobalValue>(L))
374 return Engine.equivalentAsOperands(cast<GlobalValue>(L),
375 cast<GlobalValue>(R));
377 // Compare constant expressions structurally.
378 if (isa<ConstantExpr>(L))
379 return equivalentAsOperands(cast<ConstantExpr>(L),
380 cast<ConstantExpr>(R));
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))
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();
396 bool equivalentAsOperands(ConstantExpr *L, ConstantExpr *R) {
399 if (L->getOpcode() != R->getOpcode())
402 switch (L->getOpcode()) {
403 case Instruction::ICmp:
404 case Instruction::FCmp:
405 if (L->getPredicate() != R->getPredicate())
409 case Instruction::GetElementPtr:
417 if (L->getNumOperands() != R->getNumOperands())
420 for (unsigned I = 0, E = L->getNumOperands(); I != E; ++I)
421 if (!equivalentAsOperands(L->getOperand(I), R->getOperand(I)))
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())
433 // Value subtypes: Argument, Constant, Instruction, BasicBlock,
434 // InlineAsm, MDNode, MDString, PseudoSourceValue
436 if (isa<Constant>(L))
437 return equivalentAsOperands(cast<Constant>(L), cast<Constant>(R));
439 if (isa<Instruction>(L))
440 return Values[L] == R || TentativeValues.count(std::make_pair(L, R));
442 if (isa<Argument>(L))
443 return Values[L] == R;
445 if (isa<BasicBlock>(L))
446 return Blocks[cast<BasicBlock>(L)] != R;
448 // Pretend everything else is identical.
452 // Avoid a gcc warning about accessing 'this' in an initializer.
453 FunctionDifferenceEngine *this_() { return this; }
456 FunctionDifferenceEngine(DifferenceEngine &Engine) :
457 Engine(Engine), Queue(QueueSorter(*this_())) {}
459 void diff(Function *L, Function *R) {
460 if (L->arg_size() != R->arg_size())
461 Engine.log("different argument counts");
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)
470 tryUnify(&*L->begin(), &*R->begin());
476 DiffEntry() : Cost(0) {}
479 llvm::SmallVector<char, 8> Path; // actually of DifferenceEngine::DiffChange
482 bool FunctionDifferenceEngine::matchForBlockDiff(Instruction *L,
484 return !diff(L, R, false, false);
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();
492 unsigned NL = std::distance(LStart, LE);
494 SmallVector<DiffEntry, 20> Paths1(NL+1);
495 SmallVector<DiffEntry, 20> Paths2(NL+1);
497 DiffEntry *Cur = Paths1.data();
498 DiffEntry *Next = Paths2.data();
500 const unsigned LeftCost = 2;
501 const unsigned RightCost = 2;
502 const unsigned MatchCost = 0;
504 assert(TentativeValues.empty());
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);
513 for (BasicBlock::iterator RI = RStart; RI != RE; ++RI) {
514 // Initialize the first row.
516 Next[0].Cost += RightCost;
517 Next[0].Path.push_back(DC_right);
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);
531 Next[Index] = Cur[Index];
532 Next[Index].Cost += RightCost;
533 Next[Index].Path.push_back(DC_right);
537 std::swap(Cur, Next);
540 // We don't need the tentative values anymore; everything from here
541 // on out should be non-tentative.
542 TentativeValues.clear();
544 SmallVectorImpl<char> &Path = Cur[NL].Path;
545 BasicBlock::iterator LI = LStart, RI = RStart;
547 DiffLogBuilder Diff(Engine.getConsumer());
549 // Drop trailing matches.
550 while (Path.back() == DC_match)
553 // Skip leading matches.
554 SmallVectorImpl<char>::iterator
555 PI = Path.begin(), PE = Path.end();
556 while (PI != PE && *PI == DC_match) {
561 for (; PI != PE; ++PI) {
562 switch (static_cast<DiffChange>(*PI)) {
564 assert(LI != LE && RI != RE);
566 Instruction *L = &*LI, *R = &*RI;
587 // Finishing unifying and complaining about the tails of the block,
588 // which should be matches all the way through.
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->getIterator();
603 if (I == LStart->getParent()->begin()) return;
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()))
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->getIterator();
616 if (I == RStart->getParent()->begin()) return;
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()))
623 if (!LInvoke->use_empty())
624 Values[LInvoke] = RCall;
625 tryUnify(LInvoke->getNormalDest(), RTerm->getSuccessor(0));
631 void DifferenceEngine::Oracle::anchor() { }
633 void DifferenceEngine::diff(Function *L, Function *R) {
634 Context C(*this, L, R);
637 // FIXME: attributes and CC
638 // FIXME: parameter attributes
640 // If both are declarations, we're done.
641 if (L->empty() && R->empty())
644 log("left function is declaration, right function is definition");
646 log("right function is declaration, left function is definition");
648 FunctionDifferenceEngine(*this).diff(L, R);
651 void DifferenceEngine::diff(Module *L, Module *R) {
653 SmallVector<std::pair<Function*,Function*>, 20> Queue;
655 for (Module::iterator I = L->begin(), E = L->end(); I != E; ++I) {
657 LNames.insert(LFn->getName());
659 if (Function *RFn = R->getFunction(LFn->getName()))
660 Queue.push_back(std::make_pair(LFn, RFn));
662 logf("function %l exists only in left module") << LFn;
665 for (Module::iterator I = R->begin(), E = R->end(); I != E; ++I) {
667 if (!LNames.count(RFn->getName()))
668 logf("function %r exists only in right module") << RFn;
671 for (SmallVectorImpl<std::pair<Function*,Function*> >::iterator
672 I = Queue.begin(), E = Queue.end(); I != E; ++I)
673 diff(I->first, I->second);
676 bool DifferenceEngine::equivalentAsOperands(GlobalValue *L, GlobalValue *R) {
677 if (globalValueOracle) return (*globalValueOracle)(L, R);
678 return L->getName() == R->getName();