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-//===-- DifferenceEngine.cpp - Structural function/module comparison ------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This header defines the implementation of the LLVM difference
-// engine, which structurally compares global values within a module.
-//
-//===----------------------------------------------------------------------===//
-
-#include "DifferenceEngine.h"
-
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/Module.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/DenseSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/StringSet.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Support/type_traits.h"
-
-#include <utility>
-
-using namespace llvm;
-
-namespace {
-
-/// A priority queue, implemented as a heap.
-template <class T, class Sorter, unsigned InlineCapacity>
-class PriorityQueue {
- Sorter Precedes;
- llvm::SmallVector<T, InlineCapacity> Storage;
-
-public:
- PriorityQueue(const Sorter &Precedes) : Precedes(Precedes) {}
-
- /// Checks whether the heap is empty.
- bool empty() const { return Storage.empty(); }
-
- /// Insert a new value on the heap.
- void insert(const T &V) {
- unsigned Index = Storage.size();
- Storage.push_back(V);
- if (Index == 0) return;
-
- T *data = Storage.data();
- while (true) {
- unsigned Target = (Index + 1) / 2 - 1;
- if (!Precedes(data[Index], data[Target])) return;
- std::swap(data[Index], data[Target]);
- if (Target == 0) return;
- Index = Target;
- }
- }
-
- /// Remove the minimum value in the heap. Only valid on a non-empty heap.
- T remove_min() {
- assert(!empty());
- T tmp = Storage[0];
-
- unsigned NewSize = Storage.size() - 1;
- if (NewSize) {
- // Move the slot at the end to the beginning.
- if (isPodLike<T>::value)
- Storage[0] = Storage[NewSize];
- else
- std::swap(Storage[0], Storage[NewSize]);
-
- // Bubble the root up as necessary.
- unsigned Index = 0;
- while (true) {
- // With a 1-based index, the children would be Index*2 and Index*2+1.
- unsigned R = (Index + 1) * 2;
- unsigned L = R - 1;
-
- // If R is out of bounds, we're done after this in any case.
- if (R >= NewSize) {
- // If L is also out of bounds, we're done immediately.
- if (L >= NewSize) break;
-
- // Otherwise, test whether we should swap L and Index.
- if (Precedes(Storage[L], Storage[Index]))
- std::swap(Storage[L], Storage[Index]);
- break;
- }
-
- // Otherwise, we need to compare with the smaller of L and R.
- // Prefer R because it's closer to the end of the array.
- unsigned IndexToTest = (Precedes(Storage[L], Storage[R]) ? L : R);
-
- // If Index is >= the min of L and R, then heap ordering is restored.
- if (!Precedes(Storage[IndexToTest], Storage[Index]))
- break;
-
- // Otherwise, keep bubbling up.
- std::swap(Storage[IndexToTest], Storage[Index]);
- Index = IndexToTest;
- }
- }
- Storage.pop_back();
-
- return tmp;
- }
-};
-
-/// A function-scope difference engine.
-class FunctionDifferenceEngine {
- DifferenceEngine &Engine;
-
- /// The current mapping from old local values to new local values.
- DenseMap<Value*, Value*> Values;
-
- /// The current mapping from old blocks to new blocks.
- DenseMap<BasicBlock*, BasicBlock*> Blocks;
-
- DenseSet<std::pair<Value*, Value*> > TentativeValues;
-
- unsigned getUnprocPredCount(BasicBlock *Block) const {
- unsigned Count = 0;
- for (pred_iterator I = pred_begin(Block), E = pred_end(Block); I != E; ++I)
- if (!Blocks.count(*I)) Count++;
- return Count;
- }
-
- typedef std::pair<BasicBlock*, BasicBlock*> BlockPair;
-
- /// A type which sorts a priority queue by the number of unprocessed
- /// predecessor blocks it has remaining.
- ///
- /// This is actually really expensive to calculate.
- struct QueueSorter {
- const FunctionDifferenceEngine &fde;
- explicit QueueSorter(const FunctionDifferenceEngine &fde) : fde(fde) {}
-
- bool operator()(const BlockPair &Old, const BlockPair &New) {
- return fde.getUnprocPredCount(Old.first)
- < fde.getUnprocPredCount(New.first);
- }
- };
-
- /// A queue of unified blocks to process.
- PriorityQueue<BlockPair, QueueSorter, 20> Queue;
-
- /// Try to unify the given two blocks. Enqueues them for processing
- /// if they haven't already been processed.
- ///
- /// Returns true if there was a problem unifying them.
- bool tryUnify(BasicBlock *L, BasicBlock *R) {
- BasicBlock *&Ref = Blocks[L];
-
- if (Ref) {
- if (Ref == R) return false;
-
- Engine.logf("successor %l cannot be equivalent to %r; "
- "it's already equivalent to %r")
- << L << R << Ref;
- return true;
- }
-
- Ref = R;
- Queue.insert(BlockPair(L, R));
- return false;
- }
-
- /// Unifies two instructions, given that they're known not to have
- /// structural differences.
- void unify(Instruction *L, Instruction *R) {
- DifferenceEngine::Context C(Engine, L, R);
-
- bool Result = diff(L, R, true, true);
- assert(!Result && "structural differences second time around?");
- (void) Result;
- if (!L->use_empty())
- Values[L] = R;
- }
-
- void processQueue() {
- while (!Queue.empty()) {
- BlockPair Pair = Queue.remove_min();
- diff(Pair.first, Pair.second);
- }
- }
-
- void diff(BasicBlock *L, BasicBlock *R) {
- DifferenceEngine::Context C(Engine, L, R);
-
- BasicBlock::iterator LI = L->begin(), LE = L->end();
- BasicBlock::iterator RI = R->begin(), RE = R->end();
-
- llvm::SmallVector<std::pair<Instruction*,Instruction*>, 20> TentativePairs;
-
- do {
- assert(LI != LE && RI != RE);
- Instruction *LeftI = &*LI, *RightI = &*RI;
-
- // If the instructions differ, start the more sophisticated diff
- // algorithm at the start of the block.
- if (diff(LeftI, RightI, false, false)) {
- TentativeValues.clear();
- return runBlockDiff(L->begin(), R->begin());
- }
-
- // Otherwise, tentatively unify them.
- if (!LeftI->use_empty())
- TentativeValues.insert(std::make_pair(LeftI, RightI));
-
- ++LI, ++RI;
- } while (LI != LE); // This is sufficient: we can't get equality of
- // terminators if there are residual instructions.
-
- // Unify everything in the block, non-tentatively this time.
- TentativeValues.clear();
- for (LI = L->begin(), RI = R->begin(); LI != LE; ++LI, ++RI)
- unify(&*LI, &*RI);
- }
-
- bool matchForBlockDiff(Instruction *L, Instruction *R);
- void runBlockDiff(BasicBlock::iterator LI, BasicBlock::iterator RI);
-
- bool diffCallSites(CallSite L, CallSite R, bool Complain) {
- // FIXME: call attributes
- if (!equivalentAsOperands(L.getCalledValue(), R.getCalledValue())) {
- if (Complain) Engine.log("called functions differ");
- return true;
- }
- if (L.arg_size() != R.arg_size()) {
- if (Complain) Engine.log("argument counts differ");
- return true;
- }
- for (unsigned I = 0, E = L.arg_size(); I != E; ++I)
- if (!equivalentAsOperands(L.getArgument(I), R.getArgument(I))) {
- if (Complain)
- Engine.logf("arguments %l and %r differ")
- << L.getArgument(I) << R.getArgument(I);
- return true;
- }
- return false;
- }
-
- bool diff(Instruction *L, Instruction *R, bool Complain, bool TryUnify) {
- // FIXME: metadata (if Complain is set)
-
- // Different opcodes always imply different operations.
- if (L->getOpcode() != R->getOpcode()) {
- if (Complain) Engine.log("different instruction types");
- return true;
- }
-
- if (isa<CmpInst>(L)) {
- if (cast<CmpInst>(L)->getPredicate()
- != cast<CmpInst>(R)->getPredicate()) {
- if (Complain) Engine.log("different predicates");
- return true;
- }
- } else if (isa<CallInst>(L)) {
- return diffCallSites(CallSite(L), CallSite(R), Complain);
- } else if (isa<PHINode>(L)) {
- // FIXME: implement.
-
- // This is really wierd; type uniquing is broken?
- if (L->getType() != R->getType()) {
- if (!L->getType()->isPointerTy() || !R->getType()->isPointerTy()) {
- if (Complain) Engine.log("different phi types");
- return true;
- }
- }
- return false;
-
- // Terminators.
- } else if (isa<InvokeInst>(L)) {
- InvokeInst *LI = cast<InvokeInst>(L);
- InvokeInst *RI = cast<InvokeInst>(R);
- if (diffCallSites(CallSite(LI), CallSite(RI), Complain))
- return true;
-
- if (TryUnify) {
- tryUnify(LI->getNormalDest(), RI->getNormalDest());
- tryUnify(LI->getUnwindDest(), RI->getUnwindDest());
- }
- return false;
-
- } else if (isa<BranchInst>(L)) {
- BranchInst *LI = cast<BranchInst>(L);
- BranchInst *RI = cast<BranchInst>(R);
- if (LI->isConditional() != RI->isConditional()) {
- if (Complain) Engine.log("branch conditionality differs");
- return true;
- }
-
- if (LI->isConditional()) {
- if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
- if (Complain) Engine.log("branch conditions differ");
- return true;
- }
- if (TryUnify) tryUnify(LI->getSuccessor(1), RI->getSuccessor(1));
- }
- if (TryUnify) tryUnify(LI->getSuccessor(0), RI->getSuccessor(0));
- return false;
-
- } else if (isa<SwitchInst>(L)) {
- SwitchInst *LI = cast<SwitchInst>(L);
- SwitchInst *RI = cast<SwitchInst>(R);
- if (!equivalentAsOperands(LI->getCondition(), RI->getCondition())) {
- if (Complain) Engine.log("switch conditions differ");
- return true;
- }
- if (TryUnify) tryUnify(LI->getDefaultDest(), RI->getDefaultDest());
-
- bool Difference = false;
-
- DenseMap<ConstantInt*,BasicBlock*> LCases;
- for (unsigned I = 1, E = LI->getNumCases(); I != E; ++I)
- LCases[LI->getCaseValue(I)] = LI->getSuccessor(I);
- for (unsigned I = 1, E = RI->getNumCases(); I != E; ++I) {
- ConstantInt *CaseValue = RI->getCaseValue(I);
- BasicBlock *LCase = LCases[CaseValue];
- if (LCase) {
- if (TryUnify) tryUnify(LCase, RI->getSuccessor(I));
- LCases.erase(CaseValue);
- } else if (!Difference) {
- if (Complain)
- Engine.logf("right switch has extra case %r") << CaseValue;
- Difference = true;
- }
- }
- if (!Difference)
- for (DenseMap<ConstantInt*,BasicBlock*>::iterator
- I = LCases.begin(), E = LCases.end(); I != E; ++I) {
- if (Complain)
- Engine.logf("left switch has extra case %l") << I->first;
- Difference = true;
- }
- return Difference;
- } else if (isa<UnreachableInst>(L)) {
- return false;
- }
-
- if (L->getNumOperands() != R->getNumOperands()) {
- if (Complain) Engine.log("instructions have different operand counts");
- return true;
- }
-
- for (unsigned I = 0, E = L->getNumOperands(); I != E; ++I) {
- Value *LO = L->getOperand(I), *RO = R->getOperand(I);
- if (!equivalentAsOperands(LO, RO)) {
- if (Complain) Engine.logf("operands %l and %r differ") << LO << RO;
- return true;
- }
- }
-
- return false;
- }
-
- bool equivalentAsOperands(Constant *L, Constant *R) {
- // Use equality as a preliminary filter.
- if (L == R)
- return true;
-
- if (L->getValueID() != R->getValueID())
- return false;
-
- // Ask the engine about global values.
- if (isa<GlobalValue>(L))
- return Engine.equivalentAsOperands(cast<GlobalValue>(L),
- cast<GlobalValue>(R));
-
- // Compare constant expressions structurally.
- if (isa<ConstantExpr>(L))
- return equivalentAsOperands(cast<ConstantExpr>(L),
- cast<ConstantExpr>(R));
-
- // Nulls of the "same type" don't always actually have the same
- // type; I don't know why. Just white-list them.
- if (isa<ConstantPointerNull>(L))
- return true;
-
- // Block addresses only match if we've already encountered the
- // block. FIXME: tentative matches?
- if (isa<BlockAddress>(L))
- return Blocks[cast<BlockAddress>(L)->getBasicBlock()]
- == cast<BlockAddress>(R)->getBasicBlock();
-
- return false;
- }
-
- bool equivalentAsOperands(ConstantExpr *L, ConstantExpr *R) {
- if (L == R)
- return true;
- if (L->getOpcode() != R->getOpcode())
- return false;
-
- switch (L->getOpcode()) {
- case Instruction::ICmp:
- case Instruction::FCmp:
- if (L->getPredicate() != R->getPredicate())
- return false;
- break;
-
- case Instruction::GetElementPtr:
- // FIXME: inbounds?
- break;
-
- default:
- break;
- }
-
- if (L->getNumOperands() != R->getNumOperands())
- return false;
-
- for (unsigned I = 0, E = L->getNumOperands(); I != E; ++I)
- if (!equivalentAsOperands(L->getOperand(I), R->getOperand(I)))
- return false;
-
- return true;
- }
-
- bool equivalentAsOperands(Value *L, Value *R) {
- // Fall out if the values have different kind.
- // This possibly shouldn't take priority over oracles.
- if (L->getValueID() != R->getValueID())
- return false;
-
- // Value subtypes: Argument, Constant, Instruction, BasicBlock,
- // InlineAsm, MDNode, MDString, PseudoSourceValue
-
- if (isa<Constant>(L))
- return equivalentAsOperands(cast<Constant>(L), cast<Constant>(R));
-
- if (isa<Instruction>(L))
- return Values[L] == R || TentativeValues.count(std::make_pair(L, R));
-
- if (isa<Argument>(L))
- return Values[L] == R;
-
- if (isa<BasicBlock>(L))
- return Blocks[cast<BasicBlock>(L)] != R;
-
- // Pretend everything else is identical.
- return true;
- }
-
- // Avoid a gcc warning about accessing 'this' in an initializer.
- FunctionDifferenceEngine *this_() { return this; }
-
-public:
- FunctionDifferenceEngine(DifferenceEngine &Engine) :
- Engine(Engine), Queue(QueueSorter(*this_())) {}
-
- void diff(Function *L, Function *R) {
- if (L->arg_size() != R->arg_size())
- Engine.log("different argument counts");
-
- // Map the arguments.
- for (Function::arg_iterator
- LI = L->arg_begin(), LE = L->arg_end(),
- RI = R->arg_begin(), RE = R->arg_end();
- LI != LE && RI != RE; ++LI, ++RI)
- Values[&*LI] = &*RI;
-
- tryUnify(&*L->begin(), &*R->begin());
- processQueue();
- }
-};
-
-struct DiffEntry {
- DiffEntry() : Cost(0) {}
-
- unsigned Cost;
- llvm::SmallVector<char, 8> Path; // actually of DifferenceEngine::DiffChange
-};
-
-bool FunctionDifferenceEngine::matchForBlockDiff(Instruction *L,
- Instruction *R) {
- return !diff(L, R, false, false);
-}
-
-void FunctionDifferenceEngine::runBlockDiff(BasicBlock::iterator LStart,
- BasicBlock::iterator RStart) {
- BasicBlock::iterator LE = LStart->getParent()->end();
- BasicBlock::iterator RE = RStart->getParent()->end();
-
- unsigned NL = std::distance(LStart, LE);
-
- SmallVector<DiffEntry, 20> Paths1(NL+1);
- SmallVector<DiffEntry, 20> Paths2(NL+1);
-
- DiffEntry *Cur = Paths1.data();
- DiffEntry *Next = Paths2.data();
-
- const unsigned LeftCost = 2;
- const unsigned RightCost = 2;
- const unsigned MatchCost = 0;
-
- assert(TentativeValues.empty());
-
- // Initialize the first column.
- for (unsigned I = 0; I != NL+1; ++I) {
- Cur[I].Cost = I * LeftCost;
- for (unsigned J = 0; J != I; ++J)
- Cur[I].Path.push_back(DifferenceEngine::DC_left);
- }
-
- for (BasicBlock::iterator RI = RStart; RI != RE; ++RI) {
- // Initialize the first row.
- Next[0] = Cur[0];
- Next[0].Cost += RightCost;
- Next[0].Path.push_back(DifferenceEngine::DC_right);
-
- unsigned Index = 1;
- for (BasicBlock::iterator LI = LStart; LI != LE; ++LI, ++Index) {
- if (matchForBlockDiff(&*LI, &*RI)) {
- Next[Index] = Cur[Index-1];
- Next[Index].Cost += MatchCost;
- Next[Index].Path.push_back(DifferenceEngine::DC_match);
- TentativeValues.insert(std::make_pair(&*LI, &*RI));
- } else if (Next[Index-1].Cost <= Cur[Index].Cost) {
- Next[Index] = Next[Index-1];
- Next[Index].Cost += LeftCost;
- Next[Index].Path.push_back(DifferenceEngine::DC_left);
- } else {
- Next[Index] = Cur[Index];
- Next[Index].Cost += RightCost;
- Next[Index].Path.push_back(DifferenceEngine::DC_right);
- }
- }
-
- std::swap(Cur, Next);
- }
-
- // We don't need the tentative values anymore; everything from here
- // on out should be non-tentative.
- TentativeValues.clear();
-
- SmallVectorImpl<char> &Path = Cur[NL].Path;
- BasicBlock::iterator LI = LStart, RI = RStart;
-
- DifferenceEngine::DiffLogBuilder Diff(Engine);
-
- // Drop trailing matches.
- while (Path.back() == DifferenceEngine::DC_match)
- Path.pop_back();
-
- // Skip leading matches.
- SmallVectorImpl<char>::iterator
- PI = Path.begin(), PE = Path.end();
- while (PI != PE && *PI == DifferenceEngine::DC_match) {
- unify(&*LI, &*RI);
- ++PI, ++LI, ++RI;
- }
-
- for (; PI != PE; ++PI) {
- switch (static_cast<DifferenceEngine::DiffChange>(*PI)) {
- case DifferenceEngine::DC_match:
- assert(LI != LE && RI != RE);
- {
- Instruction *L = &*LI, *R = &*RI;
- unify(L, R);
- Diff.addMatch(L, R);
- }
- ++LI; ++RI;
- break;
-
- case DifferenceEngine::DC_left:
- assert(LI != LE);
- Diff.addLeft(&*LI);
- ++LI;
- break;
-
- case DifferenceEngine::DC_right:
- assert(RI != RE);
- Diff.addRight(&*RI);
- ++RI;
- break;
- }
- }
-
- // Finishing unifying and complaining about the tails of the block,
- // which should be matches all the way through.
- while (LI != LE) {
- assert(RI != RE);
- unify(&*LI, &*RI);
- ++LI, ++RI;
- }
-
- // If the terminators have different kinds, but one is an invoke and the
- // other is an unconditional branch immediately following a call, unify
- // the results and the destinations.
- TerminatorInst *LTerm = LStart->getParent()->getTerminator();
- TerminatorInst *RTerm = RStart->getParent()->getTerminator();
- if (isa<BranchInst>(LTerm) && isa<InvokeInst>(RTerm)) {
- if (cast<BranchInst>(LTerm)->isConditional()) return;
- BasicBlock::iterator I = LTerm;
- if (I == LStart->getParent()->begin()) return;
- --I;
- if (!isa<CallInst>(*I)) return;
- CallInst *LCall = cast<CallInst>(&*I);
- InvokeInst *RInvoke = cast<InvokeInst>(RTerm);
- if (!equivalentAsOperands(LCall->getCalledValue(), RInvoke->getCalledValue()))
- return;
- if (!LCall->use_empty())
- Values[LCall] = RInvoke;
- tryUnify(LTerm->getSuccessor(0), RInvoke->getNormalDest());
- } else if (isa<InvokeInst>(LTerm) && isa<BranchInst>(RTerm)) {
- if (cast<BranchInst>(RTerm)->isConditional()) return;
- BasicBlock::iterator I = RTerm;
- if (I == RStart->getParent()->begin()) return;
- --I;
- if (!isa<CallInst>(*I)) return;
- CallInst *RCall = cast<CallInst>(I);
- InvokeInst *LInvoke = cast<InvokeInst>(LTerm);
- if (!equivalentAsOperands(LInvoke->getCalledValue(), RCall->getCalledValue()))
- return;
- if (!LInvoke->use_empty())
- Values[LInvoke] = RCall;
- tryUnify(LInvoke->getNormalDest(), RTerm->getSuccessor(0));
- }
-}
-
-}
-
-void DifferenceEngine::diff(Function *L, Function *R) {
- Context C(*this, L, R);
-
- // FIXME: types
- // FIXME: attributes and CC
- // FIXME: parameter attributes
-
- // If both are declarations, we're done.
- if (L->empty() && R->empty())
- return;
- else if (L->empty())
- log("left function is declaration, right function is definition");
- else if (R->empty())
- log("right function is declaration, left function is definition");
- else
- FunctionDifferenceEngine(*this).diff(L, R);
-}
-
-void DifferenceEngine::diff(Module *L, Module *R) {
- StringSet<> LNames;
- SmallVector<std::pair<Function*,Function*>, 20> Queue;
-
- for (Module::iterator I = L->begin(), E = L->end(); I != E; ++I) {
- Function *LFn = &*I;
- LNames.insert(LFn->getName());
-
- if (Function *RFn = R->getFunction(LFn->getName()))
- Queue.push_back(std::make_pair(LFn, RFn));
- else
- logf("function %l exists only in left module") << LFn;
- }
-
- for (Module::iterator I = R->begin(), E = R->end(); I != E; ++I) {
- Function *RFn = &*I;
- if (!LNames.count(RFn->getName()))
- logf("function %r exists only in right module") << RFn;
- }
-
- for (SmallVectorImpl<std::pair<Function*,Function*> >::iterator
- I = Queue.begin(), E = Queue.end(); I != E; ++I)
- diff(I->first, I->second);
-}
-
-bool DifferenceEngine::equivalentAsOperands(GlobalValue *L, GlobalValue *R) {
- if (globalValueOracle) return (*globalValueOracle)(L, R);
- return L->getName() == R->getName();
-}
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