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// 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_add_dead_blocks.h"
#include <algorithm>
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/transformation_add_dead_block.h"
namespace spvtools {
namespace fuzz {
namespace {
const size_t kMaxTransformationsInOnePass = 100U;
} // namespace
FuzzerPassAddDeadBlocks::FuzzerPassAddDeadBlocks(
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 FuzzerPassAddDeadBlocks::Apply() {
// We iterate over all blocks in the module collecting up those at which we
// might add a branch to a new dead block. We then loop over all such
// candidates and actually apply transformations. This separation is to
// avoid modifying the module as we traverse it.
std::vector<TransformationAddDeadBlock> candidate_transformations;
for (auto& function : *GetIRContext()->module()) {
for (auto& block : function) {
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfAddingDeadBlock())) {
continue;
}
// Make sure the module contains a boolean constant equal to
// |condition_value|.
bool condition_value = GetFuzzerContext()->ChooseEven();
FindOrCreateBoolConstant(condition_value, false);
// We speculatively create a transformation, and then apply it (below) if
// it turns out to be applicable. This avoids duplicating the logic for
// applicability checking.
//
// It means that fresh ids for transformations that turn out not to be
// applicable end up being unused.
candidate_transformations.emplace_back(TransformationAddDeadBlock(
GetFuzzerContext()->GetFreshId(), block.id(), condition_value));
}
}
// Applying transformations can be expensive as each transformation requires
// dominator information and also invalidates dominator information. We thus
// limit the number of transformations that one application of this fuzzer
// pass can apply. We choose to do this after identifying all the
// transformations that we *might* want to apply, rather than breaking the
// above loops once the limit is reached, to avoid biasing towards
// transformations that target early parts of the module.
GetFuzzerContext()->Shuffle(&candidate_transformations);
for (size_t i = 0; i < std::min(kMaxTransformationsInOnePass,
candidate_transformations.size());
i++) {
MaybeApplyTransformation(candidate_transformations[i]);
}
}
} // namespace fuzz
} // namespace spvtools
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