SPIRV-Tools/source/fuzz/fuzzer_pass_add_loop_preheaders.cpp
Stefano Milizia eade36db22
spirv-fuzz: Fuzzer pass to randomly apply loop preheaders (#3668)
This PR introduces FuzzerPassAddLoopPreheaders, which:
- Finds existing loop headers
- If they have no simple preheader (where simple means that the
  preheader itself is not a loop header), randomly decides whether
  to add one.

Fixes #3621.
2020-08-14 12:44:28 +01:00

67 lines
2.2 KiB
C++

// Copyright (c) 2020 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_loop_preheaders.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/transformation_add_loop_preheader.h"
namespace spvtools {
namespace fuzz {
FuzzerPassAddLoopPreheaders::FuzzerPassAddLoopPreheaders(
opt::IRContext* ir_context, TransformationContext* transformation_context,
FuzzerContext* fuzzer_context,
protobufs::TransformationSequence* transformations)
: FuzzerPass(ir_context, transformation_context, fuzzer_context,
transformations) {}
FuzzerPassAddLoopPreheaders::~FuzzerPassAddLoopPreheaders() = default;
void FuzzerPassAddLoopPreheaders::Apply() {
for (auto& function : *GetIRContext()->module()) {
// Keep track of all the loop headers we want to add a preheader to.
std::vector<uint32_t> loop_header_ids_to_consider;
for (auto& block : function) {
// We only care about loop headers.
if (!block.IsLoopHeader()) {
continue;
}
// Randomly decide whether to consider this header.
if (!GetFuzzerContext()->ChoosePercentage(
GetFuzzerContext()->GetChanceOfAddingLoopPreheader())) {
continue;
}
// We exclude loop headers with just one predecessor (the back-edge block)
// because they are unreachable.
if (GetIRContext()->cfg()->preds(block.id()).size() < 2) {
continue;
}
loop_header_ids_to_consider.push_back(block.id());
}
for (uint32_t header_id : loop_header_ids_to_consider) {
// If not already present, add a preheader which is not also a loop
// header.
GetOrCreateSimpleLoopPreheader(header_id);
}
}
}
} // namespace fuzz
} // namespace spvtools