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https://github.com/KhronosGroup/SPIRV-Tools
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9c4481419e
spirv-fuzz features transformations that should be applicable by construction. Assertions are used to detect when such transformations turn out to be inapplicable. Failures of such assertions indicate bugs in the fuzzer. However, when using the fuzzer at scale (e.g. in ClusterFuzz) reports of these assertion failures create noise, and cause the fuzzer to exit early. This change adds an option whereby inapplicable transformations can be ignored. This reduces noise and allows fuzzing to continue even when a transformation that should be applicable but is not has been erroneously created.
118 lines
5.2 KiB
C++
118 lines
5.2 KiB
C++
// Copyright (c) 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "source/fuzz/fuzzer_pass_adjust_loop_controls.h"
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#include "source/fuzz/transformation_set_loop_control.h"
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namespace spvtools {
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namespace fuzz {
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FuzzerPassAdjustLoopControls::FuzzerPassAdjustLoopControls(
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opt::IRContext* ir_context, TransformationContext* transformation_context,
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FuzzerContext* fuzzer_context,
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protobufs::TransformationSequence* transformations,
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bool ignore_inapplicable_transformations)
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: FuzzerPass(ir_context, transformation_context, fuzzer_context,
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transformations, ignore_inapplicable_transformations) {}
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void FuzzerPassAdjustLoopControls::Apply() {
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// Consider every merge instruction in the module (via looking through all
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// functions and blocks).
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for (auto& function : *GetIRContext()->module()) {
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for (auto& block : function) {
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if (auto merge_inst = block.GetMergeInst()) {
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// Ignore the instruction if it is not a loop merge.
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if (merge_inst->opcode() != SpvOpLoopMerge) {
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continue;
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}
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// Decide randomly whether to adjust this loop merge.
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if (!GetFuzzerContext()->ChoosePercentage(
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GetFuzzerContext()->GetChanceOfAdjustingLoopControl())) {
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continue;
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}
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uint32_t existing_mask = merge_inst->GetSingleWordOperand(
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TransformationSetLoopControl::kLoopControlMaskInOperandIndex);
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// First, set the new mask to one of None, Unroll or DontUnroll.
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std::vector<uint32_t> basic_masks = {SpvLoopControlMaskNone,
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SpvLoopControlUnrollMask,
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SpvLoopControlDontUnrollMask};
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uint32_t new_mask =
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basic_masks[GetFuzzerContext()->RandomIndex(basic_masks)];
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// For the loop controls that depend on guarantees about what the loop
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// does, check which of these were present in the existing mask and
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// randomly decide whether to keep them. They are just hints, so
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// removing them should not change the semantics of the module.
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for (auto mask_bit :
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{SpvLoopControlDependencyInfiniteMask,
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SpvLoopControlDependencyLengthMask,
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SpvLoopControlMinIterationsMask, SpvLoopControlMaxIterationsMask,
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SpvLoopControlIterationMultipleMask}) {
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if ((existing_mask & mask_bit) && GetFuzzerContext()->ChooseEven()) {
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// The mask bits we are considering are not available in all SPIR-V
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// versions. However, we only include a mask bit if it was present
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// in the original loop control mask, and we work under the
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// assumption that we are transforming a valid module, thus we don't
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// need to actually check whether the SPIR-V version being used
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// supports these loop control mask bits.
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new_mask |= mask_bit;
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}
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}
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// We use 0 for peel count and partial count in the case that we choose
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// not to set these controls.
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uint32_t peel_count = 0;
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uint32_t partial_count = 0;
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// PeelCount and PartialCount are not compatible with DontUnroll, so
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// we check whether DontUnroll is set.
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if (!(new_mask & SpvLoopControlDontUnrollMask)) {
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// If PeelCount is supported by this SPIR-V version, randomly choose
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// whether to set it. If it was set in the original mask and is not
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// selected for setting here, that amounts to dropping it.
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if (TransformationSetLoopControl::PeelCountIsSupported(
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GetIRContext()) &&
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GetFuzzerContext()->ChooseEven()) {
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new_mask |= SpvLoopControlPeelCountMask;
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// The peel count is chosen randomly - if PeelCount was already set
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// this will overwrite whatever peel count was previously used.
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peel_count = GetFuzzerContext()->GetRandomLoopControlPeelCount();
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}
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// Similar, but for PartialCount.
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if (TransformationSetLoopControl::PartialCountIsSupported(
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GetIRContext()) &&
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GetFuzzerContext()->ChooseEven()) {
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new_mask |= SpvLoopControlPartialCountMask;
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partial_count =
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GetFuzzerContext()->GetRandomLoopControlPartialCount();
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}
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}
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// Apply the transformation and add it to the output transformation
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// sequence.
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TransformationSetLoopControl transformation(block.id(), new_mask,
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peel_count, partial_count);
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ApplyTransformation(transformation);
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}
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}
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}
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}
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} // namespace fuzz
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} // namespace spvtools
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