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https://github.com/KhronosGroup/SPIRV-Tools
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1dc2458060
This pass will look for adjacent loops that are compatible and legal to
be fused.
Loops are compatible if:
- they both have one induction variable
- they have the same upper and lower bounds
- same initial value
- same condition
- they have the same update step
- they are adjacent
- there are no break/continue in either of them
Fusion is legal if:
- fused loops do not have any dependencies with dependence distance
greater than 0 that did not exist in the original loops.
- there are no function calls in the loops (could have side-effects)
- there are no barriers in the loops
It will fuse all such loops as long as the number of registers used for
the fused loop stays under the threshold defined by
max_registers_per_loop.
52 lines
1.8 KiB
C++
52 lines
1.8 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_LOOP_FUSION_PASS_H_
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#define SOURCE_OPT_LOOP_FUSION_PASS_H_
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#include "opt/pass.h"
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namespace spvtools {
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namespace opt {
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// Implements a loop fusion pass.
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// This pass will look for adjacent loops that are compatible and legal to be
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// fused. It will fuse all such loops as long as the register usage for the
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// fused loop stays under the threshold defined by |max_registers_per_loop|.
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class LoopFusionPass : public Pass {
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public:
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explicit LoopFusionPass(size_t max_registers_per_loop)
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: Pass(), max_registers_per_loop_(max_registers_per_loop) {}
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const char* name() const override { return "loop-fusion"; }
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// Processes the given |module|. Returns Status::Failure if errors occur when
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// processing. Returns the corresponding Status::Success if processing is
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// succesful to indicate whether changes have been made to the modue.
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Status Process(ir::IRContext* c) override;
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private:
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// Fuse loops in |function| if compatible, legal and the fused loop won't use
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// too many registers.
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bool ProcessFunction(ir::Function* function);
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// The maximum number of registers a fused loop is allowed to use.
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size_t max_registers_per_loop_;
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};
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} // namespace opt
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} // namespace spvtools
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#endif // SOURCE_OPT_LOOP_FUSION_PASS_H_
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