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https://github.com/KhronosGroup/SPIRV-Tools
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82663f34c9
Merge return assumes that the only unreachable blocks are those needed to keep the structured cfg valid. Even those must be essentially empty blocks. If this is not the case, we get unpredictable behaviour. This commit add a check in merge return, and emits an error if it is not the case. Added a pass of dead branch elimination before merge return in both the performance and size passes. It is a precondition of merge return. Fixes #1962.
102 lines
3.5 KiB
C++
102 lines
3.5 KiB
C++
// Copyright (c) 2018 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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#ifndef SOURCE_OPT_STRUCT_CFG_ANALYSIS_H_
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#define SOURCE_OPT_STRUCT_CFG_ANALYSIS_H_
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#include <unordered_map>
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#include "source/opt/function.h"
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#include "source/util/bit_vector.h"
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namespace spvtools {
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namespace opt {
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class IRContext;
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// An analysis that, for each basic block, finds the constructs in which it is
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// contained, so we can easily get headers and merge nodes.
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class StructuredCFGAnalysis {
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public:
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explicit StructuredCFGAnalysis(IRContext* ctx);
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// Returns the id of the header of the innermost merge construct
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// that contains |bb_id|. Returns |0| if |bb_id| is not contained in any
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// merge construct.
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uint32_t ContainingConstruct(uint32_t bb_id) {
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auto it = bb_to_construct_.find(bb_id);
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if (it == bb_to_construct_.end()) {
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return 0;
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}
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return it->second.containing_construct;
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}
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// Returns the id of the merge block of the innermost merge construct
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// that contains |bb_id|. Returns |0| if |bb_id| is not contained in any
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// merge construct.
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uint32_t MergeBlock(uint32_t bb_id);
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// Returns the id of the header of the innermost loop construct
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// that contains |bb_id|. Return |0| if |bb_id| is not contained in any loop
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// construct.
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uint32_t ContainingLoop(uint32_t bb_id) {
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auto it = bb_to_construct_.find(bb_id);
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if (it == bb_to_construct_.end()) {
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return 0;
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}
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return it->second.containing_loop;
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}
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// Returns the id of the merge block of the innermost loop construct
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// that contains |bb_id|. Return |0| if |bb_id| is not contained in any loop
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// construct.
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uint32_t LoopMergeBlock(uint32_t bb_id);
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// Returns the id of the continue block of the innermost loop construct
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// that contains |bb_id|. Return |0| if |bb_id| is not contained in any loop
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// construct.
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uint32_t LoopContinueBlock(uint32_t bb_id);
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bool IsContinueBlock(uint32_t bb_id);
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bool IsMergeBlock(uint32_t bb_id);
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private:
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// Struct used to hold the information for a basic block.
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// |containing_construct| is the header for the innermost containing
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// construct, or 0 if no such construct exists. It could be a selection
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// construct or a loop construct. |containing_loop| is the innermost
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// containing loop construct, or 0 if the basic bloc is not in a loop. If the
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// basic block is in a selection construct that is contained in a loop
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// construct, then these two values will not be the same.
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struct ConstructInfo {
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uint32_t containing_construct;
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uint32_t containing_loop;
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};
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// Populates |bb_to_construct_| with the innermost containing merge and loop
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// constructs for each basic block in |func|.
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void AddBlocksInFunction(Function* func);
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IRContext* context_;
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// A map from a basic block to the headers of its inner most containing
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// constructs.
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std::unordered_map<uint32_t, ConstructInfo> bb_to_construct_;
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utils::BitVector merge_blocks_;
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};
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} // namespace opt
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} // namespace spvtools
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#endif // SOURCE_OPT_STRUCT_CFG_ANALYSIS_H_
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