| // 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_adjust_loop_controls.h" |
| |
| #include "source/fuzz/transformation_set_loop_control.h" |
| |
| namespace spvtools { |
| namespace fuzz { |
| |
| FuzzerPassAdjustLoopControls::FuzzerPassAdjustLoopControls( |
| 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 FuzzerPassAdjustLoopControls::Apply() { |
| // Consider every merge instruction in the module (via looking through all |
| // functions and blocks). |
| for (auto& function : *GetIRContext()->module()) { |
| for (auto& block : function) { |
| if (auto merge_inst = block.GetMergeInst()) { |
| // Ignore the instruction if it is not a loop merge. |
| if (merge_inst->opcode() != SpvOpLoopMerge) { |
| continue; |
| } |
| |
| // Decide randomly whether to adjust this loop merge. |
| if (!GetFuzzerContext()->ChoosePercentage( |
| GetFuzzerContext()->GetChanceOfAdjustingLoopControl())) { |
| continue; |
| } |
| |
| uint32_t existing_mask = merge_inst->GetSingleWordOperand( |
| TransformationSetLoopControl::kLoopControlMaskInOperandIndex); |
| |
| // First, set the new mask to one of None, Unroll or DontUnroll. |
| std::vector<uint32_t> basic_masks = {SpvLoopControlMaskNone, |
| SpvLoopControlUnrollMask, |
| SpvLoopControlDontUnrollMask}; |
| uint32_t new_mask = |
| basic_masks[GetFuzzerContext()->RandomIndex(basic_masks)]; |
| |
| // For the loop controls that depend on guarantees about what the loop |
| // does, check which of these were present in the existing mask and |
| // randomly decide whether to keep them. They are just hints, so |
| // removing them should not change the semantics of the module. |
| for (auto mask_bit : |
| {SpvLoopControlDependencyInfiniteMask, |
| SpvLoopControlDependencyLengthMask, |
| SpvLoopControlMinIterationsMask, SpvLoopControlMaxIterationsMask, |
| SpvLoopControlIterationMultipleMask}) { |
| if ((existing_mask & mask_bit) && GetFuzzerContext()->ChooseEven()) { |
| // The mask bits we are considering are not available in all SPIR-V |
| // versions. However, we only include a mask bit if it was present |
| // in the original loop control mask, and we work under the |
| // assumption that we are transforming a valid module, thus we don't |
| // need to actually check whether the SPIR-V version being used |
| // supports these loop control mask bits. |
| new_mask |= mask_bit; |
| } |
| } |
| |
| // We use 0 for peel count and partial count in the case that we choose |
| // not to set these controls. |
| uint32_t peel_count = 0; |
| uint32_t partial_count = 0; |
| |
| // PeelCount and PartialCount are not compatible with DontUnroll, so |
| // we check whether DontUnroll is set. |
| if (!(new_mask & SpvLoopControlDontUnrollMask)) { |
| // If PeelCount is supported by this SPIR-V version, randomly choose |
| // whether to set it. If it was set in the original mask and is not |
| // selected for setting here, that amounts to dropping it. |
| if (TransformationSetLoopControl::PeelCountIsSupported( |
| GetIRContext()) && |
| GetFuzzerContext()->ChooseEven()) { |
| new_mask |= SpvLoopControlPeelCountMask; |
| // The peel count is chosen randomly - if PeelCount was already set |
| // this will overwrite whatever peel count was previously used. |
| peel_count = GetFuzzerContext()->GetRandomLoopControlPeelCount(); |
| } |
| // Similar, but for PartialCount. |
| if (TransformationSetLoopControl::PartialCountIsSupported( |
| GetIRContext()) && |
| GetFuzzerContext()->ChooseEven()) { |
| new_mask |= SpvLoopControlPartialCountMask; |
| partial_count = |
| GetFuzzerContext()->GetRandomLoopControlPartialCount(); |
| } |
| } |
| |
| // Apply the transformation and add it to the output transformation |
| // sequence. |
| TransformationSetLoopControl transformation(block.id(), new_mask, |
| peel_count, partial_count); |
| ApplyTransformation(transformation); |
| } |
| } |
| } |
| } |
| |
| } // namespace fuzz |
| } // namespace spvtools |