mirror of
https://github.com/KhronosGroup/SPIRV-Tools
synced 2024-10-19 03:20:14 +00:00
e2e95172df
Before this change there was quite a lot of duplication in the code being used to choose random percentages, and some of it was incorrect so that a percentage chance of (100-N)% instead of N% was being used. Also there was a lot of duplicate code to choose a random index into a vector. This change eliminates that duplication (fixing up the percentage problem), and gets rid of direct access to the random number generator being used for fuzzing, so that all randomization requests must go through the FuzzerContext class, discouraging future ad-hoc uses of the random number generator.
83 lines
3.0 KiB
C++
83 lines
3.0 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, FactManager* fact_manager,
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FuzzerContext* fuzzer_context,
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protobufs::TransformationSequence* transformations)
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: FuzzerPass(ir_context, fact_manager, fuzzer_context, 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 (transformation.IsApplicable(GetIRContext(), *GetFactManager())) {
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transformation.Apply(GetIRContext(), GetFactManager());
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*GetTransformations()->add_transformation() =
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transformation.ToMessage();
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} else {
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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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