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