| // 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_pass_outline_functions.h" |
| |
| #include <vector> |
| |
| #include "source/fuzz/fuzzer_util.h" |
| #include "source/fuzz/instruction_descriptor.h" |
| #include "source/fuzz/transformation_outline_function.h" |
| #include "source/fuzz/transformation_split_block.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| FuzzerPassOutlineFunctions::FuzzerPassOutlineFunctions( |
| opt::IRContext* ir_context, TransformationContext* transformation_context, |
| FuzzerContext* fuzzer_context, |
| protobufs::TransformationSequence* transformations, |
| bool ignore_inapplicable_transformations) |
| : FuzzerPass(ir_context, transformation_context, fuzzer_context, |
| transformations, ignore_inapplicable_transformations) {} |
| |
| void FuzzerPassOutlineFunctions::Apply() { |
| std::vector<opt::Function*> original_functions; |
| for (auto& function : *GetIRContext()->module()) { |
| original_functions.push_back(&function); |
| } |
| for (auto& function : original_functions) { |
| if (!GetFuzzerContext()->ChoosePercentage( |
| GetFuzzerContext()->GetChanceOfOutliningFunction())) { |
| continue; |
| } |
| std::vector<opt::BasicBlock*> blocks; |
| for (auto& block : *function) { |
| blocks.push_back(&block); |
| } |
| auto entry_block = MaybeGetEntryBlockSuitableForOutlining( |
| blocks[GetFuzzerContext()->RandomIndex(blocks)]); |
| |
| if (!entry_block) { |
| // The chosen block is not suitable to be the entry block of a region that |
| // will be outlined. |
| continue; |
| } |
| |
| auto dominator_analysis = GetIRContext()->GetDominatorAnalysis(function); |
| auto postdominator_analysis = |
| GetIRContext()->GetPostDominatorAnalysis(function); |
| std::vector<opt::BasicBlock*> candidate_exit_blocks; |
| for (auto postdominates_entry_block = entry_block; |
| postdominates_entry_block != nullptr; |
| postdominates_entry_block = postdominator_analysis->ImmediateDominator( |
| postdominates_entry_block)) { |
| // Consider the block if it is dominated by the entry block, ignore it if |
| // it is a continue target. |
| if (dominator_analysis->Dominates(entry_block, |
| postdominates_entry_block) && |
| !GetIRContext()->GetStructuredCFGAnalysis()->IsContinueBlock( |
| postdominates_entry_block->id())) { |
| candidate_exit_blocks.push_back(postdominates_entry_block); |
| } |
| } |
| if (candidate_exit_blocks.empty()) { |
| continue; |
| } |
| auto exit_block = MaybeGetExitBlockSuitableForOutlining( |
| candidate_exit_blocks[GetFuzzerContext()->RandomIndex( |
| candidate_exit_blocks)]); |
| |
| if (!exit_block) { |
| // The block chosen is not suitable |
| continue; |
| } |
| |
| auto region_blocks = TransformationOutlineFunction::GetRegionBlocks( |
| GetIRContext(), entry_block, exit_block); |
| std::map<uint32_t, uint32_t> input_id_to_fresh_id; |
| for (auto id : TransformationOutlineFunction::GetRegionInputIds( |
| GetIRContext(), region_blocks, exit_block)) { |
| input_id_to_fresh_id[id] = GetFuzzerContext()->GetFreshId(); |
| } |
| std::map<uint32_t, uint32_t> output_id_to_fresh_id; |
| for (auto id : TransformationOutlineFunction::GetRegionOutputIds( |
| GetIRContext(), region_blocks, exit_block)) { |
| output_id_to_fresh_id[id] = GetFuzzerContext()->GetFreshId(); |
| } |
| TransformationOutlineFunction transformation( |
| entry_block->id(), exit_block->id(), |
| /*new_function_struct_return_type_id*/ |
| GetFuzzerContext()->GetFreshId(), |
| /*new_function_type_id*/ GetFuzzerContext()->GetFreshId(), |
| /*new_function_id*/ GetFuzzerContext()->GetFreshId(), |
| /*new_function_region_entry_block*/ |
| GetFuzzerContext()->GetFreshId(), |
| /*new_caller_result_id*/ GetFuzzerContext()->GetFreshId(), |
| /*new_callee_result_id*/ GetFuzzerContext()->GetFreshId(), |
| /*input_id_to_fresh_id*/ input_id_to_fresh_id, |
| /*output_id_to_fresh_id*/ output_id_to_fresh_id); |
| MaybeApplyTransformation(transformation); |
| } |
| } |
| |
| opt::BasicBlock* |
| FuzzerPassOutlineFunctions::MaybeGetEntryBlockSuitableForOutlining( |
| opt::BasicBlock* entry_block) { |
| // If the entry block is a loop header, we need to get or create its |
| // preheader and make it the entry block, if possible. |
| if (entry_block->IsLoopHeader()) { |
| auto predecessors = |
| GetIRContext()->cfg()->preds(entry_block->GetLabel()->result_id()); |
| |
| if (predecessors.size() < 2) { |
| // The header only has one predecessor (the back-edge block) and thus |
| // it is unreachable. The block cannot be adjusted to be suitable for |
| // outlining. |
| return nullptr; |
| } |
| |
| // Get or create a suitable preheader and make it become the entry block. |
| entry_block = |
| GetOrCreateSimpleLoopPreheader(entry_block->GetLabel()->result_id()); |
| } |
| |
| assert(!entry_block->IsLoopHeader() && |
| "The entry block cannot be a loop header at this point."); |
| |
| // If the entry block starts with OpPhi or OpVariable, try to split it. |
| if (entry_block->begin()->opcode() == spv::Op::OpPhi || |
| entry_block->begin()->opcode() == spv::Op::OpVariable) { |
| // Find the first non-OpPhi and non-OpVariable instruction. |
| auto non_phi_or_var_inst = &*entry_block->begin(); |
| while (non_phi_or_var_inst->opcode() == spv::Op::OpPhi || |
| non_phi_or_var_inst->opcode() == spv::Op::OpVariable) { |
| non_phi_or_var_inst = non_phi_or_var_inst->NextNode(); |
| } |
| |
| // Split the block. |
| uint32_t new_block_id = GetFuzzerContext()->GetFreshId(); |
| ApplyTransformation(TransformationSplitBlock( |
| MakeInstructionDescriptor(GetIRContext(), non_phi_or_var_inst), |
| new_block_id)); |
| |
| // The new entry block is the newly-created block. |
| entry_block = &*entry_block->GetParent()->FindBlock(new_block_id); |
| } |
| |
| return entry_block; |
| } |
| |
| opt::BasicBlock* |
| FuzzerPassOutlineFunctions::MaybeGetExitBlockSuitableForOutlining( |
| opt::BasicBlock* exit_block) { |
| // The exit block must not be a continue target. |
| assert(!GetIRContext()->GetStructuredCFGAnalysis()->IsContinueBlock( |
| exit_block->id()) && |
| "A candidate exit block cannot be a continue target."); |
| |
| // If the exit block is a merge block, try to split it and return the second |
| // block in the pair as the exit block. |
| if (GetIRContext()->GetStructuredCFGAnalysis()->IsMergeBlock( |
| exit_block->id())) { |
| uint32_t new_block_id = GetFuzzerContext()->GetFreshId(); |
| |
| // Find the first non-OpPhi instruction, after which to split. |
| auto split_before = &*exit_block->begin(); |
| while (split_before->opcode() == spv::Op::OpPhi) { |
| split_before = split_before->NextNode(); |
| } |
| |
| if (!MaybeApplyTransformation(TransformationSplitBlock( |
| MakeInstructionDescriptor(GetIRContext(), split_before), |
| new_block_id))) { |
| return nullptr; |
| } |
| |
| return &*exit_block->GetParent()->FindBlock(new_block_id); |
| } |
| |
| return exit_block; |
| } |
| |
| } // namespace fuzz |
| } // namespace spvtools |
