SPIRV-Tools/source/fuzz/fuzzer_pass_permute_blocks.cpp
Alastair Donaldson 8d4261bc44
spirv-fuzz: Introduce TransformationContext (#3272)
Some transformations (e.g. TransformationAddFunction) rely on running
the validator to decide whether the transformation is applicable.  A
recent change allowed spirv-fuzz to take validator options, to cater
for the case where a module should be considered valid under
particular conditions.  However, validation during the checking of
transformations had no access to these validator options.

This change introduced TransformationContext, which currently consists
of a fact manager and a set of validator options, but could in the
future have other fields corresponding to other objects that it is
useful to have access to when applying transformations.  Now, instead
of checking and applying transformations in the context of a
FactManager, a TransformationContext is used.  This gives access to
the fact manager as before, and also access to the validator options
when they are needed.
2020-04-02 15:54:46 +01:00

85 lines
3.1 KiB
C++

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