diff options
Diffstat (limited to 'lib/Expr/ArrayExprOptimizer.cpp')
| -rw-r--r-- | lib/Expr/ArrayExprOptimizer.cpp | 456 |
1 files changed, 455 insertions, 1 deletions
diff --git a/lib/Expr/ArrayExprOptimizer.cpp b/lib/Expr/ArrayExprOptimizer.cpp index d3e8cbab..86c19a81 100644 --- a/lib/Expr/ArrayExprOptimizer.cpp +++ b/lib/Expr/ArrayExprOptimizer.cpp @@ -11,11 +11,26 @@ namespace klee { llvm::cl::opt<ArrayOptimizationType> OptimizeArray( "optimize-array", llvm::cl::values( + clEnumValN(ALL, "all", "Combining index and value transformations"), clEnumValN(INDEX, "index", "Index-based transformation"), + clEnumValN(VALUE, "value", "Value-based transformation at branch (both " + "concrete and concrete/symbolic)"), clEnumValEnd), llvm::cl::init(NONE), llvm::cl::desc("Optimize accesses to either concrete or concrete/symbolic " "arrays. (default=off)")); + +llvm::cl::opt<double> ArrayValueRatio( + "array-value-ratio", + llvm::cl::desc("Maximum ratio of unique values to array size for which the " + "value-based transformations are applied."), + llvm::cl::init(1.0), llvm::cl::value_desc("Unique Values / Array Size")); + +llvm::cl::opt<double> ArrayValueSymbRatio( + "array-value-symb-ratio", + llvm::cl::desc("Maximum ratio of symbolic values to array size for which " + "the mixed value-based transformations are applied."), + llvm::cl::init(1.0), llvm::cl::value_desc("Symbolic Values / Array Size")); }; void ExprOptimizer::optimizeExpr(const ref<Expr> &e, ref<Expr> &result, @@ -33,7 +48,7 @@ void ExprOptimizer::optimizeExpr(const ref<Expr> &e, ref<Expr> &result, } // ----------------------- INDEX-BASED OPTIMIZATION ------------------------- - if (!valueOnly && OptimizeArray == INDEX) { + if (!valueOnly && (OptimizeArray == ALL || OptimizeArray == INDEX)) { array2idx_ty arrays; ConstantArrayExprVisitor aev(arrays); aev.visit(e); @@ -72,6 +87,31 @@ void ExprOptimizer::optimizeExpr(const ref<Expr> &e, ref<Expr> &result, } } } + // ----------------------- VALUE-BASED OPTIMIZATION ------------------------- + if (OptimizeArray == VALUE || + (OptimizeArray == ALL && (!result.get() || valueOnly))) { + std::vector<const ReadExpr *> reads; + std::map<const ReadExpr *, std::pair<unsigned, Expr::Width> > readInfo; + ArrayReadExprVisitor are(reads, readInfo); + are.visit(e); + std::reverse(reads.begin(), reads.end()); + + if (reads.size() == 0 || are.isIncompatible()) { + cacheExprUnapplicable.insert(hash); + return; + } + + ref<Expr> selectOpt = + getSelectOptExpr(e, reads, readInfo, are.containsSymbolic()); + if (selectOpt.get()) { + klee_warning("OPT_V: successful"); + result = selectOpt; + cacheExprOptimized[hash] = result; + } else { + klee_warning("OPT_V: unsuccessful"); + cacheExprUnapplicable.insert(hash); + } + } } bool ExprOptimizer::computeIndexes(array2idx_ty &arrays, const ref<Expr> &e, @@ -133,3 +173,417 @@ bool ExprOptimizer::computeIndexes(array2idx_ty &arrays, const ref<Expr> &e, } return success; } + +ref<Expr> ExprOptimizer::getSelectOptExpr( + const ref<Expr> &e, std::vector<const ReadExpr *> &reads, + std::map<const ReadExpr *, std::pair<unsigned, Expr::Width> > &readInfo, + bool isSymbolic) { + ref<Expr> notFound; + ref<Expr> toReturn; + + // Array is concrete + if (!isSymbolic) { + std::map<unsigned, ref<Expr> > optimized; + for (auto &read : reads) { + auto info = readInfo[read]; + auto cached = cacheReadExprOptimized.find(read->hash()); + if (cached != cacheReadExprOptimized.end()) { + optimized.insert(std::make_pair(info.first, (*cached).second)); + continue; + } + Expr::Width width = read->getWidth(); + if (info.second > width) { + width = info.second; + } + unsigned size = read->updates.root->getSize(); + unsigned bytesPerElement = width / 8; + unsigned elementsInArray = size / bytesPerElement; + + // Note: we already filtered the ReadExpr, so here we can safely + // assume that the UpdateNodes contain ConstantExpr indexes and values + assert(read->updates.root->isConstantArray() && + "Expected concrete array, found symbolic array"); + auto arrayConstValues = read->updates.root->constantValues; + for (const UpdateNode *un = read->updates.head; un; un = un->next) { + ConstantExpr *ce = static_cast<ConstantExpr *>(un->index.get()); + uint64_t index = ce->getAPValue().getZExtValue(); + assert(index < arrayConstValues.size()); + ConstantExpr *arrayValue = static_cast<ConstantExpr *>(un->value.get()); + arrayConstValues[index] = arrayValue; + } + std::vector<uint64_t> arrayValues; + // Get the concrete values from the array + for (unsigned i = 0; i < elementsInArray; i++) { + uint64_t val = 0; + for (unsigned j = 0; j < bytesPerElement; j++) { + val |= (*( + arrayConstValues[(i * bytesPerElement) + j] + .get() + ->getAPValue() + .getRawData()) + << (j * 8)); + } + arrayValues.push_back(val); + } + + ref<Expr> index = read->index; + IndexCleanerVisitor ice; + ice.visit(index); + if (ice.getIndex().get()) { + index = ice.getIndex(); + } + + ref<Expr> opt = + buildConstantSelectExpr(index, arrayValues, width, elementsInArray); + if (opt.get()) { + cacheReadExprOptimized[read->hash()] = opt; + optimized.insert(std::make_pair(info.first, opt)); + } + } + ArrayValueOptReplaceVisitor replacer(optimized); + toReturn = replacer.visit(e); + } + + // Array is mixed concrete/symbolic + // \pre: array is concrete && updatelist contains at least one symbolic value + // OR + // array is symbolic && updatelist contains at least one concrete value + else { + std::map<unsigned, ref<Expr> > optimized; + for (auto &read : reads) { + auto info = readInfo[read]; + auto cached = cacheReadExprOptimized.find(read->hash()); + if (cached != cacheReadExprOptimized.end()) { + optimized.insert(std::make_pair(info.first, (*cached).second)); + continue; + } + Expr::Width width = read->getWidth(); + if (info.second > width) { + width = info.second; + } + unsigned size = read->updates.root->getSize(); + unsigned bytesPerElement = width / 8; + unsigned elementsInArray = size / bytesPerElement; + bool symbArray = read->updates.root->isSymbolicArray(); + + BitArray ba(size, symbArray); + // Note: we already filtered the ReadExpr, so here we can safely + // assume that the UpdateNodes contain ConstantExpr indexes, but in + // this case we *cannot* assume anything on the values + auto arrayConstValues = read->updates.root->constantValues; + if (arrayConstValues.size() < size) { + // We need to "force" initialization of the values + for (size_t i = arrayConstValues.size(); i < size; i++) { + arrayConstValues.push_back(ConstantExpr::create(0, Expr::Int8)); + } + } + for (const UpdateNode *un = read->updates.head; un; un = un->next) { + ConstantExpr *ce = static_cast<ConstantExpr *>(un->index.get()); + uint64_t index = ce->getAPValue().getLimitedValue(); + if (!isa<ConstantExpr>(un->value)) { + ba.set(index); + } else { + ba.unset(index); + ConstantExpr *arrayValue = + static_cast<ConstantExpr *>(un->value.get()); + arrayConstValues[index] = arrayValue; + } + } + + std::vector<std::pair<uint64_t, bool> > arrayValues; + unsigned symByteNum = 0; + for (unsigned i = 0; i < elementsInArray; i++) { + uint64_t val = 0; + bool elementIsConcrete = true; + for (unsigned j = 0; j < bytesPerElement; j++) { + if (ba.get((i * bytesPerElement) + j)) { + elementIsConcrete = false; + break; + } else { + val |= (*( + arrayConstValues[(i * bytesPerElement) + j] + .get() + ->getAPValue() + .getRawData()) + << (j * 8)); + } + } + if (elementIsConcrete) { + arrayValues.push_back(std::make_pair(val, true)); + } else { + symByteNum++; + arrayValues.push_back(std::make_pair(0, false)); + } + } + + if (((double)symByteNum / (double)elementsInArray) <= ArrayValueSymbRatio) { + // If the optimization can be applied we apply it + // Build the dynamic select expression + ref<Expr> opt = + buildMixedSelectExpr(read, arrayValues, width, elementsInArray); + if (opt.get()) { + cacheReadExprOptimized[read->hash()] = opt; + optimized.insert(std::make_pair(info.first, opt)); + } + } + } + ArrayValueOptReplaceVisitor replacer(optimized, false); + toReturn = replacer.visit(e); + } + + return toReturn.get() ? toReturn : notFound; +} + +ref<Expr> ExprOptimizer::buildConstantSelectExpr( + const ref<Expr> &index, std::vector<uint64_t> &arrayValues, + Expr::Width width, unsigned arraySize) const { + std::vector<std::pair<uint64_t, uint64_t> > ranges; + std::vector<uint64_t> values; + std::set<uint64_t> unique_array_values; + ExprBuilder *builder = createDefaultExprBuilder(); + Expr::Width valWidth = width; + ref<Expr> result; + + ref<Expr> actualIndex; + if (index->getWidth() > Expr::Int32) { + actualIndex = ExtractExpr::alloc(index, 0, Expr::Int32); + } else { + actualIndex = index; + } + Expr::Width idxWidth = actualIndex->getWidth(); + + // Calculate the repeating values ranges in the constant array + unsigned curr_idx = 0; + uint64_t curr_val = arrayValues[0]; + for (unsigned i = 0; i < arraySize; i++) { + uint64_t temp = arrayValues[i]; + unique_array_values.insert(curr_val); + if (temp != curr_val) { + ranges.push_back(std::make_pair(curr_idx, i)); + values.push_back(curr_val); + curr_val = temp; + curr_idx = i; + if (i == (arraySize - 1)) { + ranges.push_back(std::make_pair(curr_idx, i + 1)); + values.push_back(curr_val); + } + } else if (i == (arraySize - 1)) { + ranges.push_back(std::make_pair(curr_idx, i + 1)); + values.push_back(curr_val); + } + } + + if (((double)unique_array_values.size() / (double)(arraySize)) >= ArrayValueRatio) { + return result; + } + + std::map<uint64_t, std::vector<std::pair<uint64_t, uint64_t> > > exprMap; + for (size_t i = 0; i < ranges.size(); i++) { + if (exprMap.find(values[i]) != exprMap.end()) { + exprMap[values[i]] + .push_back(std::make_pair(ranges[i].first, ranges[i].second)); + } else { + if (exprMap.find(values[i]) == exprMap.end()) { + exprMap.insert(std::make_pair( + values[i], std::vector<std::pair<uint64_t, uint64_t> >())); + } + exprMap.find(values[i]) + ->second.push_back(std::make_pair(ranges[i].first, ranges[i].second)); + } + } + + int ct = 0; + // For each range appropriately build the Select expression. + for (auto range : exprMap) { + ref<Expr> temp; + if (ct == 0) { + temp = builder->Constant(llvm::APInt(valWidth, range.first, false)); + } else { + if (range.second.size() == 1) { + if (range.second[0].first == (range.second[0].second - 1)) { + temp = SelectExpr::create( + EqExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].first, false))), + builder->Constant(llvm::APInt(valWidth, range.first, false)), + result); + + } else { + temp = SelectExpr::create( + AndExpr::create( + SgeExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].first, false))), + SltExpr::create( + actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].second, false)))), + builder->Constant(llvm::APInt(valWidth, range.first, false)), + result); + } + + } else { + ref<Expr> currOr; + if (range.second[0].first == (range.second[0].second - 1)) { + currOr = EqExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].first, false))); + } else { + currOr = AndExpr::create( + SgeExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].first, false))), + SltExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[0].second, false)))); + } + for (size_t i = 1; i < range.second.size(); i++) { + ref<Expr> tempOr; + if (range.second[i].first == (range.second[i].second - 1)) { + tempOr = OrExpr::create( + EqExpr::create(actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[i].first, false))), + currOr); + + } else { + tempOr = OrExpr::create( + AndExpr::create( + SgeExpr::create( + actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[i].first, false))), + SltExpr::create( + actualIndex, + builder->Constant(llvm::APInt( + idxWidth, range.second[i].second, false)))), + currOr); + } + currOr = tempOr; + } + temp = SelectExpr::create(currOr, builder->Constant(llvm::APInt( + valWidth, range.first, false)), + result); + } + } + result = temp; + ct++; + } + + delete (builder); + + return result; +} + +ref<Expr> ExprOptimizer::buildMixedSelectExpr( + const ReadExpr *re, std::vector<std::pair<uint64_t, bool> > &arrayValues, + Expr::Width width, unsigned elementsInArray) const { + ExprBuilder *builder = createDefaultExprBuilder(); + std::vector<uint64_t> values; + std::vector<std::pair<uint64_t, uint64_t> > ranges; + std::vector<uint64_t> holes; + std::set<uint64_t> unique_array_values; + + unsigned arraySize = elementsInArray; + unsigned curr_idx = 0; + uint64_t curr_val = arrayValues[0].first; + + bool emptyRange = true; + // Calculate Range values + for (size_t i = 0; i < arrayValues.size(); i++) { + // If the value is concrete + if (arrayValues[i].second) { + // The range contains a concrete value + emptyRange = false; + uint64_t temp = arrayValues[i].first; + unique_array_values.insert(temp); + if (temp != curr_val) { + ranges.push_back(std::make_pair(curr_idx, i)); + values.push_back(curr_val); + curr_val = temp; + curr_idx = i; + if (i == (arraySize - 1)) { + ranges.push_back(std::make_pair(curr_idx, curr_idx + 1)); + values.push_back(curr_val); + } + } else if (i == (arraySize - 1)) { + ranges.push_back(std::make_pair(curr_idx, i + 1)); + values.push_back(curr_val); + } + } else { + holes.push_back(i); + // If this is not an empty range + if (!emptyRange) { + ranges.push_back(std::make_pair(curr_idx, i)); + values.push_back(curr_val); + } + curr_val = arrayValues[i + 1].first; + curr_idx = i + 1; + emptyRange = true; + } + } + + assert(unique_array_values.size() > 0 && "No unique values"); + assert(ranges.size() > 0 && "No ranges"); + + ref<Expr> result; + if (((double)unique_array_values.size() / (double)(arraySize)) <= ArrayValueRatio) { + // The final "else" expression will be the original unoptimized array read + // expression + unsigned range_start = 0; + if (holes.size() == 0) { + result = builder->Constant(llvm::APInt(width, values[0], false)); + range_start = 1; + } else { + ref<Expr> firstIndex = MulExpr::create( + ConstantExpr::create(holes[0], re->index->getWidth()), + ConstantExpr::create(width / 8, re->index->getWidth())); + result = ReadExpr::extendRead(re->updates, firstIndex, width); + for (size_t i = 1; i < holes.size(); i++) { + ref<Expr> temp_idx = MulExpr::create( + ConstantExpr::create(holes[i], re->index->getWidth()), + ConstantExpr::create(width / 8, re->index->getWidth())); + ref<Expr> cond = EqExpr::create( + re->index, ConstantExpr::create(holes[i], re->index->getWidth())); + ref<Expr> temp = SelectExpr::create( + cond, ReadExpr::extendRead(re->updates, temp_idx, width), result); + result = temp; + } + } + + ref<Expr> new_index = re->index; + IndexCleanerVisitor ice; + ice.visit(new_index); + if (ice.getIndex().get()) { + new_index = ice.getIndex(); + } + + int new_index_width = new_index->getWidth(); + // Iterate through all the ranges + for (size_t i = range_start; i < ranges.size(); i++) { + ref<Expr> temp; + if (ranges[i].second - 1 == ranges[i].first) { + ref<Expr> cond = EqExpr::create( + new_index, ConstantExpr::create(ranges[i].first, new_index_width)); + ref<Expr> t = ConstantExpr::create(values[i], width); + ref<Expr> f = result; + temp = SelectExpr::create(cond, t, f); + } else { + // Create the select constraint + ref<Expr> cond = AndExpr::create( + SgeExpr::create(new_index, ConstantExpr::create(ranges[i].first, + new_index_width)), + SltExpr::create(new_index, ConstantExpr::create(ranges[i].second, + new_index_width))); + ref<Expr> t = ConstantExpr::create(values[i], width); + ref<Expr> f = result; + temp = SelectExpr::create(cond, t, f); + } + result = temp; + } + } + + delete (builder); + + return result; +} |