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// Copyright (c) 2020 Vasyl Teliman
//
// 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_wrap_regions_in_selections.h"
#include "source/fuzz/fuzzer_context.h"
#include "source/fuzz/instruction_descriptor.h"
#include "source/fuzz/transformation_split_block.h"
#include "source/fuzz/transformation_wrap_region_in_selection.h"
namespace spvtools {
namespace fuzz {
FuzzerPassWrapRegionsInSelections::FuzzerPassWrapRegionsInSelections(
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 FuzzerPassWrapRegionsInSelections::Apply() {
for (auto& function : *GetIRContext()->module()) {
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfWrappingRegionInSelection())) {
continue;
}
// It is easier to select an element at random from a vector than from an
// instruction list.
std::vector<opt::BasicBlock*> header_block_candidates;
for (auto& block : function) {
header_block_candidates.push_back(&block);
}
if (header_block_candidates.empty()) {
continue;
}
// Try to get a header block candidate that will increase the chances of the
// transformation being applicable.
auto* header_block_candidate = MaybeGetHeaderBlockCandidate(
header_block_candidates[GetFuzzerContext()->RandomIndex(
header_block_candidates)]);
if (!header_block_candidate) {
continue;
}
std::vector<opt::BasicBlock*> merge_block_candidates;
for (auto& block : function) {
if (GetIRContext()->GetDominatorAnalysis(&function)->StrictlyDominates(
header_block_candidate, &block) &&
GetIRContext()
->GetPostDominatorAnalysis(&function)
->StrictlyDominates(&block, header_block_candidate)) {
merge_block_candidates.push_back(&block);
}
}
if (merge_block_candidates.empty()) {
continue;
}
// Try to get a merge block candidate that will increase the chances of the
// transformation being applicable.
auto* merge_block_candidate = MaybeGetMergeBlockCandidate(
merge_block_candidates[GetFuzzerContext()->RandomIndex(
merge_block_candidates)]);
if (!merge_block_candidate) {
continue;
}
if (!TransformationWrapRegionInSelection::IsApplicableToBlockRange(
GetIRContext(), header_block_candidate->id(),
merge_block_candidate->id())) {
continue;
}
// This boolean constant will be used as a condition for the
// OpBranchConditional instruction. We mark it as irrelevant to be able to
// replace it with a more interesting value later.
auto branch_condition = GetFuzzerContext()->ChooseEven();
FindOrCreateBoolConstant(branch_condition, true);
ApplyTransformation(TransformationWrapRegionInSelection(
header_block_candidate->id(), merge_block_candidate->id(),
branch_condition));
}
}
opt::BasicBlock*
FuzzerPassWrapRegionsInSelections::MaybeGetHeaderBlockCandidate(
opt::BasicBlock* header_block_candidate) {
// Try to create a preheader if |header_block_candidate| is a loop header.
if (header_block_candidate->IsLoopHeader()) {
// GetOrCreateSimpleLoopPreheader only supports reachable blocks.
return GetIRContext()->cfg()->preds(header_block_candidate->id()).size() ==
1
? nullptr
: GetOrCreateSimpleLoopPreheader(header_block_candidate->id());
}
// Try to split |header_block_candidate| if it's already a header block.
if (header_block_candidate->GetMergeInst()) {
SplitBlockAfterOpPhiOrOpVariable(header_block_candidate->id());
}
return header_block_candidate;
}
opt::BasicBlock* FuzzerPassWrapRegionsInSelections::MaybeGetMergeBlockCandidate(
opt::BasicBlock* merge_block_candidate) {
// If |merge_block_candidate| is a merge block of some construct, try to split
// it and return a newly created block.
if (GetIRContext()->GetStructuredCFGAnalysis()->IsMergeBlock(
merge_block_candidate->id())) {
// We can't split a merge block if it's also a loop header.
return merge_block_candidate->IsLoopHeader()
? nullptr
: SplitBlockAfterOpPhiOrOpVariable(merge_block_candidate->id());
}
return merge_block_candidate;
}
} // namespace fuzz
} // namespace spvtools
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