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// Copyright (c) 2018 Google Inc.
//
// 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/opt/workaround1209.h"
#include <list>
#include <memory>
#include <stack>
#include <utility>
namespace spvtools {
namespace opt {
Pass::Status Workaround1209::Process() {
bool modified = false;
modified = RemoveOpUnreachableInLoops();
return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
}
bool Workaround1209::RemoveOpUnreachableInLoops() {
bool modified = false;
for (auto& func : *get_module()) {
std::list<BasicBlock*> structured_order;
cfg()->ComputeStructuredOrder(&func, &*func.begin(), &structured_order);
// Keep track of the loop merges. The top of the stack will always be the
// loop merge for the loop that immediately contains the basic block being
// processed.
std::stack<uint32_t> loop_merges;
for (BasicBlock* bb : structured_order) {
if (!loop_merges.empty() && bb->id() == loop_merges.top()) {
loop_merges.pop();
}
if (bb->tail()->opcode() == spv::Op::OpUnreachable) {
if (!loop_merges.empty()) {
// We found an OpUnreachable inside a loop.
// Replace it with an unconditional branch to the loop merge.
context()->KillInst(&*bb->tail());
std::unique_ptr<Instruction> new_branch(
new Instruction(context(), spv::Op::OpBranch, 0, 0,
{{spv_operand_type_t::SPV_OPERAND_TYPE_ID,
{loop_merges.top()}}}));
context()->AnalyzeDefUse(&*new_branch);
bb->AddInstruction(std::move(new_branch));
modified = true;
}
} else {
if (bb->GetLoopMergeInst()) {
loop_merges.push(bb->MergeBlockIdIfAny());
}
}
}
}
return modified;
}
} // namespace opt
} // namespace spvtools