| // Copyright (c) 2019 Google LLC |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "source/fuzz/fuzzer_util.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| namespace fuzzerutil { |
| |
| bool IsFreshId(opt::IRContext* context, uint32_t id) { |
| return !context->get_def_use_mgr()->GetDef(id); |
| } |
| |
| void UpdateModuleIdBound(opt::IRContext* context, uint32_t id) { |
| // TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2541) consider the |
| // case where the maximum id bound is reached. |
| context->module()->SetIdBound( |
| std::max(context->module()->id_bound(), id + 1)); |
| } |
| |
| opt::BasicBlock* MaybeFindBlock(opt::IRContext* context, |
| uint32_t maybe_block_id) { |
| auto inst = context->get_def_use_mgr()->GetDef(maybe_block_id); |
| if (inst == nullptr) { |
| // No instruction defining this id was found. |
| return nullptr; |
| } |
| if (inst->opcode() != SpvOpLabel) { |
| // The instruction defining the id is not a label, so it cannot be a block |
| // id. |
| return nullptr; |
| } |
| return context->cfg()->block(maybe_block_id); |
| } |
| |
| bool PhiIdsOkForNewEdge( |
| opt::IRContext* context, opt::BasicBlock* bb_from, opt::BasicBlock* bb_to, |
| const google::protobuf::RepeatedField<google::protobuf::uint32>& phi_ids) { |
| if (bb_from->IsSuccessor(bb_to)) { |
| // There is already an edge from |from_block| to |to_block|, so there is |
| // no need to extend OpPhi instructions. Do not allow phi ids to be |
| // present. This might turn out to be too strict; perhaps it would be OK |
| // just to ignore the ids in this case. |
| return phi_ids.empty(); |
| } |
| // The edge would add a previously non-existent edge from |from_block| to |
| // |to_block|, so we go through the given phi ids and check that they exactly |
| // match the OpPhi instructions in |to_block|. |
| uint32_t phi_index = 0; |
| // An explicit loop, rather than applying a lambda to each OpPhi in |bb_to|, |
| // makes sense here because we need to increment |phi_index| for each OpPhi |
| // instruction. |
| for (auto& inst : *bb_to) { |
| if (inst.opcode() != SpvOpPhi) { |
| // The OpPhi instructions all occur at the start of the block; if we find |
| // a non-OpPhi then we have seen them all. |
| break; |
| } |
| if (phi_index == static_cast<uint32_t>(phi_ids.size())) { |
| // Not enough phi ids have been provided to account for the OpPhi |
| // instructions. |
| return false; |
| } |
| // Look for an instruction defining the next phi id. |
| opt::Instruction* phi_extension = |
| context->get_def_use_mgr()->GetDef(phi_ids[phi_index]); |
| if (!phi_extension) { |
| // The id given to extend this OpPhi does not exist. |
| return false; |
| } |
| if (phi_extension->type_id() != inst.type_id()) { |
| // The instruction given to extend this OpPhi either does not have a type |
| // or its type does not match that of the OpPhi. |
| return false; |
| } |
| |
| if (context->get_instr_block(phi_extension)) { |
| // The instruction defining the phi id has an associated block (i.e., it |
| // is not a global value). Check whether its definition dominates the |
| // exit of |from_block|. |
| auto dominator_analysis = |
| context->GetDominatorAnalysis(bb_from->GetParent()); |
| if (!dominator_analysis->Dominates(phi_extension, |
| bb_from->terminator())) { |
| // The given id is no good as its definition does not dominate the exit |
| // of |from_block| |
| return false; |
| } |
| } |
| phi_index++; |
| } |
| // Return false if not all of the ids for extending OpPhi instructions are |
| // needed. This might turn out to be stricter than necessary; perhaps it would |
| // be OK just to not use the ids in this case. |
| return phi_index == static_cast<uint32_t>(phi_ids.size()); |
| } |
| |
| void AddUnreachableEdgeAndUpdateOpPhis( |
| opt::IRContext* context, opt::BasicBlock* bb_from, opt::BasicBlock* bb_to, |
| bool condition_value, |
| const google::protobuf::RepeatedField<google::protobuf::uint32>& phi_ids) { |
| assert(PhiIdsOkForNewEdge(context, bb_from, bb_to, phi_ids) && |
| "Precondition on phi_ids is not satisfied"); |
| assert(bb_from->terminator()->opcode() == SpvOpBranch && |
| "Precondition on terminator of bb_from is not satisfied"); |
| |
| // Get the id of the boolean constant to be used as the condition. |
| opt::analysis::Bool bool_type; |
| opt::analysis::BoolConstant bool_constant( |
| context->get_type_mgr()->GetRegisteredType(&bool_type)->AsBool(), |
| condition_value); |
| uint32_t bool_id = context->get_constant_mgr()->FindDeclaredConstant( |
| &bool_constant, context->get_type_mgr()->GetId(&bool_type)); |
| |
| const bool from_to_edge_already_exists = bb_from->IsSuccessor(bb_to); |
| auto successor = bb_from->terminator()->GetSingleWordInOperand(0); |
| |
| // Add the dead branch, by turning OpBranch into OpBranchConditional, and |
| // ordering the targets depending on whether the given boolean corresponds to |
| // true or false. |
| bb_from->terminator()->SetOpcode(SpvOpBranchConditional); |
| bb_from->terminator()->SetInOperands( |
| {{SPV_OPERAND_TYPE_ID, {bool_id}}, |
| {SPV_OPERAND_TYPE_ID, {condition_value ? successor : bb_to->id()}}, |
| {SPV_OPERAND_TYPE_ID, {condition_value ? bb_to->id() : successor}}}); |
| |
| // Update OpPhi instructions in the target block if this branch adds a |
| // previously non-existent edge from source to target. |
| if (!from_to_edge_already_exists) { |
| uint32_t phi_index = 0; |
| for (auto& inst : *bb_to) { |
| if (inst.opcode() != SpvOpPhi) { |
| break; |
| } |
| assert(phi_index < static_cast<uint32_t>(phi_ids.size()) && |
| "There should be exactly one phi id per OpPhi instruction."); |
| inst.AddOperand({SPV_OPERAND_TYPE_ID, {phi_ids[phi_index]}}); |
| inst.AddOperand({SPV_OPERAND_TYPE_ID, {bb_from->id()}}); |
| phi_index++; |
| } |
| assert(phi_index == static_cast<uint32_t>(phi_ids.size()) && |
| "There should be exactly one phi id per OpPhi instruction."); |
| } |
| } |
| |
| bool BlockIsInLoopContinueConstruct(opt::IRContext* context, uint32_t block_id, |
| uint32_t maybe_loop_header_id) { |
| // We deem a block to be part of a loop's continue construct if the loop's |
| // continue target dominates the block. |
| auto containing_construct_block = context->cfg()->block(maybe_loop_header_id); |
| if (containing_construct_block->IsLoopHeader()) { |
| auto continue_target = containing_construct_block->ContinueBlockId(); |
| if (context->GetDominatorAnalysis(containing_construct_block->GetParent()) |
| ->Dominates(continue_target, block_id)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| opt::BasicBlock::iterator GetIteratorForInstruction( |
| opt::BasicBlock* block, const opt::Instruction* inst) { |
| for (auto inst_it = block->begin(); inst_it != block->end(); ++inst_it) { |
| if (inst == &*inst_it) { |
| return inst_it; |
| } |
| } |
| return block->end(); |
| } |
| |
| bool NewEdgeRespectsUseDefDominance(opt::IRContext* context, |
| opt::BasicBlock* bb_from, |
| opt::BasicBlock* bb_to) { |
| assert(bb_from->terminator()->opcode() == SpvOpBranch); |
| |
| // If there is *already* an edge from |bb_from| to |bb_to|, then adding |
| // another edge is fine from a dominance point of view. |
| if (bb_from->terminator()->GetSingleWordInOperand(0) == bb_to->id()) { |
| return true; |
| } |
| |
| // TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2919): the |
| // solution below to determining whether a new edge respects dominance |
| // rules is incomplete. Test |
| // TransformationAddDeadContinueTest::DISABLED_Miscellaneous6 exposes the |
| // problem. In practice, this limitation does not bite too often, and the |
| // worst it does is leads to SPIR-V that spirv-val rejects. |
| |
| // Let us assume that the module being manipulated is valid according to the |
| // rules of the SPIR-V language. |
| // |
| // Suppose that some block Y is dominated by |bb_to| (which includes the case |
| // where Y = |bb_to|). |
| // |
| // Suppose that Y uses an id i that is defined in some other block X. |
| // |
| // Because the module is valid, X must dominate Y. We are concerned about |
| // whether an edge from |bb_from| to |bb_to| could *stop* X from dominating |
| // Y. |
| // |
| // Because |bb_to| dominates Y, a new edge from |bb_from| to |bb_to| can |
| // only affect whether X dominates Y if X dominates |bb_to|. |
| // |
| // So let us assume that X does dominate |bb_to|, so that we have: |
| // |
| // (X defines i) dominates |bb_to| dominates (Y uses i) |
| // |
| // The new edge from |bb_from| to |bb_to| will stop the definition of i in X |
| // from dominating the use of i in Y exactly when the new edge will stop X |
| // from dominating |bb_to|. |
| // |
| // Now, the block X that we are worried about cannot dominate |bb_from|, |
| // because in that case X would still dominate |bb_to| after we add an edge |
| // from |bb_from| to |bb_to|. |
| // |
| // Also, it cannot be that X = |bb_to|, because nothing can stop a block |
| // from dominating itself. |
| // |
| // So we are looking for a block X such that: |
| // |
| // - X strictly dominates |bb_to| |
| // - X does not dominate |bb_from| |
| // - X defines an id i |
| // - i is used in some block Y |
| // - |bb_to| dominates Y |
| |
| // Walk the dominator tree backwards, starting from the immediate dominator |
| // of |bb_to|. We can stop when we find a block that also dominates |
| // |bb_from|. |
| auto dominator_analysis = context->GetDominatorAnalysis(bb_from->GetParent()); |
| for (auto dominator = dominator_analysis->ImmediateDominator(bb_to); |
| dominator != nullptr && |
| !dominator_analysis->Dominates(dominator, bb_from); |
| dominator = dominator_analysis->ImmediateDominator(dominator)) { |
| // |dominator| is a candidate for block X in the above description. |
| // We now look through the instructions for a candidate instruction i. |
| for (auto& inst : *dominator) { |
| // Consider all the uses of this instruction. |
| if (!context->get_def_use_mgr()->WhileEachUse( |
| &inst, |
| [bb_to, context, dominator_analysis]( |
| opt::Instruction* user, uint32_t operand_index) -> bool { |
| // If this use is in an OpPhi, we need to check that dominance |
| // of the relevant *parent* block is not spoiled. Otherwise we |
| // need to check that dominance of the block containing the use |
| // is not spoiled. |
| opt::BasicBlock* use_block_or_phi_parent = |
| user->opcode() == SpvOpPhi |
| ? context->cfg()->block( |
| user->GetSingleWordOperand(operand_index + 1)) |
| : context->get_instr_block(user); |
| |
| // There might not be any relevant block, e.g. if the use is in |
| // a decoration; in this case the new edge is unproblematic. |
| if (use_block_or_phi_parent == nullptr) { |
| return true; |
| } |
| |
| // With reference to the above discussion, |
| // |use_block_or_phi_parent| is a candidate for the block Y. |
| // If |bb_to| dominates this block, the new edge would be |
| // problematic. |
| return !dominator_analysis->Dominates(bb_to, |
| use_block_or_phi_parent); |
| })) { |
| return false; |
| } |
| } |
| } |
| return true; |
| } |
| |
| bool BlockIsReachableInItsFunction(opt::IRContext* context, |
| opt::BasicBlock* bb) { |
| auto enclosing_function = bb->GetParent(); |
| return context->GetDominatorAnalysis(enclosing_function) |
| ->Dominates(enclosing_function->entry().get(), bb); |
| } |
| |
| bool CanInsertOpcodeBeforeInstruction( |
| SpvOp opcode, const opt::BasicBlock::iterator& instruction_in_block) { |
| if (instruction_in_block->PreviousNode() && |
| (instruction_in_block->PreviousNode()->opcode() == SpvOpLoopMerge || |
| instruction_in_block->PreviousNode()->opcode() == SpvOpSelectionMerge)) { |
| // We cannot insert directly after a merge instruction. |
| return false; |
| } |
| if (opcode != SpvOpVariable && |
| instruction_in_block->opcode() == SpvOpVariable) { |
| // We cannot insert a non-OpVariable instruction directly before a |
| // variable; variables in a function must be contiguous in the entry block. |
| return false; |
| } |
| // We cannot insert a non-OpPhi instruction directly before an OpPhi, because |
| // OpPhi instructions need to be contiguous at the start of a block. |
| return opcode == SpvOpPhi || instruction_in_block->opcode() != SpvOpPhi; |
| } |
| |
| bool CanMakeSynonymOf(opt::IRContext* ir_context, opt::Instruction* inst) { |
| if (!inst->HasResultId()) { |
| // We can only make a synonym of an instruction that generates an id. |
| return false; |
| } |
| if (!inst->type_id()) { |
| // We can only make a synonym of an instruction that has a type. |
| return false; |
| } |
| // We do not make synonyms of objects that have decorations: if the synonym is |
| // not decorated analogously, using the original object vs. its synonymous |
| // form may not be equivalent. |
| return ir_context->get_decoration_mgr() |
| ->GetDecorationsFor(inst->result_id(), true) |
| .empty(); |
| } |
| |
| bool IsCompositeType(const opt::analysis::Type* type) { |
| return type && (type->AsArray() || type->AsMatrix() || type->AsStruct() || |
| type->AsVector()); |
| } |
| |
| } // namespace fuzzerutil |
| |
| } // namespace fuzz |
| } // namespace spvtools |
