| // 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_split_blocks.h" |
| |
| #include <utility> |
| #include <vector> |
| |
| #include "source/fuzz/transformation_split_block.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| FuzzerPassSplitBlocks::FuzzerPassSplitBlocks( |
| opt::IRContext* ir_context, FactManager* fact_manager, |
| FuzzerContext* fuzzer_context, |
| protobufs::TransformationSequence* transformations) |
| : FuzzerPass(ir_context, fact_manager, fuzzer_context, transformations) {} |
| |
| FuzzerPassSplitBlocks::~FuzzerPassSplitBlocks() = default; |
| |
| void FuzzerPassSplitBlocks::Apply() { |
| // Gather up pointers to all the blocks in the module. We are then able to |
| // iterate over these pointers and split the blocks to which they point; |
| // we cannot safely split blocks while we iterate through the module. |
| std::vector<opt::BasicBlock*> blocks; |
| for (auto& function : *GetIRContext()->module()) { |
| for (auto& block : function) { |
| blocks.push_back(&block); |
| } |
| } |
| |
| // Now go through all the block pointers that were gathered. |
| for (auto& block : blocks) { |
| // Probabilistically decide whether to try to split this block. |
| if (GetFuzzerContext()->GetRandomGenerator()->RandomPercentage() > |
| GetFuzzerContext()->GetChanceOfSplittingBlock()) { |
| continue; |
| } |
| // We are going to try to split this block. We now need to choose where |
| // to split it. We do this by finding a base instruction that has a |
| // result id, and an offset from that base instruction. We would like |
| // offsets to be as small as possible and ideally 0 - we only need offsets |
| // because not all instructions can be identified by a result id (e.g. |
| // OpStore instructions cannot). |
| std::vector<std::pair<uint32_t, uint32_t>> base_offset_pairs; |
| // The initial base instruction is the block label. |
| uint32_t base = block->id(); |
| uint32_t offset = 0; |
| // Consider every instruction in the block. The label is excluded: it is |
| // only necessary to consider it as a base in case the first instruction |
| // in the block does not have a result id. |
| for (auto& inst : *block) { |
| if (inst.HasResultId()) { |
| // In the case that the instruction has a result id, we use the |
| // instruction as its own base, with zero offset. |
| base = inst.result_id(); |
| offset = 0; |
| } else { |
| // The instruction does not have a result id, so we need to identify |
| // it via the latest instruction that did have a result id (base), and |
| // an incremented offset. |
| offset++; |
| } |
| base_offset_pairs.emplace_back(base, offset); |
| } |
| // Having identified all the places we might be able to split the block, |
| // we choose one of them. |
| auto base_offset = base_offset_pairs |
| [GetFuzzerContext()->GetRandomGenerator()->RandomUint32( |
| static_cast<uint32_t>(base_offset_pairs.size()))]; |
| auto transformation = |
| TransformationSplitBlock(base_offset.first, base_offset.second, |
| GetFuzzerContext()->GetFreshId()); |
| // If the position we have chosen turns out to be a valid place to split |
| // the block, we apply the split. Otherwise the block just doesn't get |
| // split. |
| if (transformation.IsApplicable(GetIRContext(), *GetFactManager())) { |
| transformation.Apply(GetIRContext(), GetFactManager()); |
| *GetTransformations()->add_transformation() = transformation.ToMessage(); |
| } |
| } |
| } |
| |
| } // namespace fuzz |
| } // namespace spvtools |