SPIRV-Tools/source/fuzz/transformation_merge_blocks.cpp
Alastair Donaldson b8587c984a
spirv-reduce: Allow merging unreachable blocks (#4303)
This change allows the reducer to merge together blocks even when they
are unreachable, but keeps the restriction of reachability in place
for the optimizer.

Fixes #4302.
2021-06-28 23:05:30 +01:00

90 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/transformation_merge_blocks.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/opt/block_merge_util.h"
namespace spvtools {
namespace fuzz {
TransformationMergeBlocks::TransformationMergeBlocks(
protobufs::TransformationMergeBlocks message)
: message_(std::move(message)) {}
TransformationMergeBlocks::TransformationMergeBlocks(uint32_t block_id) {
message_.set_block_id(block_id);
}
bool TransformationMergeBlocks::IsApplicable(
opt::IRContext* ir_context, const TransformationContext& /*unused*/) const {
auto second_block =
fuzzerutil::MaybeFindBlock(ir_context, message_.block_id());
// The given block must exist.
if (!second_block) {
return false;
}
// The block must have just one predecessor.
auto predecessors = ir_context->cfg()->preds(second_block->id());
if (predecessors.size() != 1) {
return false;
}
auto first_block = ir_context->cfg()->block(predecessors.at(0));
if (!ir_context->IsReachable(*first_block)) {
return false;
}
return opt::blockmergeutil::CanMergeWithSuccessor(ir_context, first_block);
}
void TransformationMergeBlocks::Apply(opt::IRContext* ir_context,
TransformationContext* /*unused*/) const {
auto second_block =
fuzzerutil::MaybeFindBlock(ir_context, message_.block_id());
auto first_block = ir_context->cfg()->block(
ir_context->cfg()->preds(second_block->id()).at(0));
auto function = first_block->GetParent();
// We need an iterator pointing to the predecessor, hence the loop.
for (auto bi = function->begin(); bi != function->end(); ++bi) {
if (bi->id() == first_block->id()) {
assert(opt::blockmergeutil::CanMergeWithSuccessor(ir_context, &*bi) &&
"Because 'Apply' should only be invoked if 'IsApplicable' holds, "
"it must be possible to merge |bi| with its successor.");
opt::blockmergeutil::MergeWithSuccessor(ir_context, function, bi);
// Invalidate all analyses, since we have changed the module
// significantly.
ir_context->InvalidateAnalysesExceptFor(opt::IRContext::kAnalysisNone);
return;
}
}
assert(false &&
"Control should not reach here - we should always find the desired "
"block");
}
protobufs::Transformation TransformationMergeBlocks::ToMessage() const {
protobufs::Transformation result;
*result.mutable_merge_blocks() = message_;
return result;
}
std::unordered_set<uint32_t> TransformationMergeBlocks::GetFreshIds() const {
return std::unordered_set<uint32_t>();
}
} // namespace fuzz
} // namespace spvtools