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https://github.com/KhronosGroup/SPIRV-Tools
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34d4294c2c
We have come across a driver bug where and OpUnreachable inside a loop is causing the shader to go into an infinite loop. This commit will try to avoid this bug by turning OpUnreachable instructions that are contained in a loop into branches to the loop merge block. This is not added to "-O" and "-Os" because it should only be used if the driver being targeted has this problem. Fixes #1209.
69 lines
2.3 KiB
C++
69 lines
2.3 KiB
C++
// Copyright (c) 2018 Google Inc.
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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 "workaround1209.h"
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#include <list>
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#include <stack>
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namespace spvtools {
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namespace opt {
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Pass::Status Workaround1209::Process(ir::IRContext* c) {
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InitializeProcessing(c);
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bool modified = false;
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modified = RemoveOpUnreachableInLoops();
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return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
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}
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bool Workaround1209::RemoveOpUnreachableInLoops() {
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bool modified = false;
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for (auto& func : *get_module()) {
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std::list<ir::BasicBlock*> structured_order;
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cfg()->ComputeStructuredOrder(&func, &*func.begin(), &structured_order);
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// Keep track of the loop merges. The top of the stack will always be the
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// loop merge for the loop that immediately contains the basic block being
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// processed.
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std::stack<uint32_t> loop_merges;
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for (ir::BasicBlock* bb : structured_order) {
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if (!loop_merges.empty() && bb->id() == loop_merges.top()) {
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loop_merges.pop();
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}
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if (bb->tail()->opcode() == SpvOpUnreachable) {
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if (!loop_merges.empty()) {
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// We found an OpUnreachable inside a loop.
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// Replace it with an unconditional branch to the loop merge.
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context()->KillInst(&*bb->tail());
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std::unique_ptr<ir::Instruction> new_branch(
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new ir::Instruction(context(), SpvOpBranch, 0, 0,
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{{spv_operand_type_t::SPV_OPERAND_TYPE_ID,
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{loop_merges.top()}}}));
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context()->AnalyzeDefUse(&*new_branch);
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bb->AddInstruction(std::move(new_branch));
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modified = true;
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}
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} else {
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if (bb->GetLoopMergeInst()) {
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loop_merges.push(bb->MergeBlockIdIfAny());
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}
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}
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}
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}
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return modified;
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}
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} // namespace opt
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} // namespace spvtools
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