mirror of
https://github.com/KhronosGroup/SPIRV-Tools
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80 lines
2.9 KiB
C++
80 lines
2.9 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_permute_blocks.h"
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#include "source/fuzz/transformation_move_block_down.h"
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namespace spvtools {
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namespace fuzz {
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FuzzerPassPermuteBlocks::FuzzerPassPermuteBlocks(
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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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: FuzzerPass(ir_context, transformation_context, fuzzer_context,
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transformations) {}
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FuzzerPassPermuteBlocks::~FuzzerPassPermuteBlocks() = default;
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void FuzzerPassPermuteBlocks::Apply() {
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// For now we do something very simple: we randomly decide whether to move a
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// block, and for each block that we do move, we push it down as far as we
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// legally can.
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// TODO(https://github.com/KhronosGroup/SPIRV-Tools/issues/2635): it would be
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// nice to randomly sample from the set of legal block permutations and then
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// encode the chosen permutation via a series of move-block-down
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// transformations. This should be possible but will require some thought.
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for (auto& function : *GetIRContext()->module()) {
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std::vector<uint32_t> block_ids;
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// Collect all block ids for the function before messing with block
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// ordering.
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for (auto& block : function) {
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block_ids.push_back(block.id());
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}
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// Now consider each block id. We consider block ids in reverse, because
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// e.g. in code generated from the following:
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//
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// if (...) {
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// A
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// B
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// } else {
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// C
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// }
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//
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// block A cannot be moved down, but B has freedom to move and that movement
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// would provide more freedom for A to move.
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for (auto id = block_ids.rbegin(); id != block_ids.rend(); ++id) {
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// Randomly decide whether to ignore the block id.
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if (!GetFuzzerContext()->ChoosePercentage(
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GetFuzzerContext()->GetChanceOfMovingBlockDown())) {
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continue;
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}
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// Keep pushing the block down, until pushing down fails.
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// The loop is guaranteed to terminate because a block cannot be pushed
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// down indefinitely.
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while (true) {
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TransformationMoveBlockDown transformation(*id);
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if (!MaybeApplyTransformation(transformation)) {
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break;
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}
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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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