63 lines
1.9 KiB
C++
63 lines
1.9 KiB
C++
/* Copyright 2018 The OpenXLA Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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==============================================================================*/
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#ifndef XLA_SERVICE_GATHER_EXPANDER_H_
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#define XLA_SERVICE_GATHER_EXPANDER_H_
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#include "xla/service/op_expander_pass.h"
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namespace xla {
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// This pass rewrites gather operations into (roughly) while loops of dynamic
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// slices.
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//
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// This pass can be used two ways:
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//
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// - kEliminateAllGathers: For backends that don't support gather, this pass
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// can convert every gather to a loop.
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//
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// - kEliminateSimpleGathers: For backends that *do* support gather, this pass
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// can strength-reduce "simple" gathers -- specifically, gathers that can be
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// represented without a loop -- to dyanmic-slices.
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//
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// Note that even in kEliminateSimpleGathers mode, this pass may still expand a
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// gather into a loop (with a trip-count of 1). It's up to other simplification
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// passes to remove the loop.
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//
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class GatherExpander : public OpExpanderPass {
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public:
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enum Mode {
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kEliminateAllGathers,
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kEliminateSimpleGathers,
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};
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explicit GatherExpander(Mode m) : mode_(m) {}
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absl::string_view name() const override { return "gather_expander"; }
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protected:
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bool InstructionMatchesPattern(HloInstruction* instruction) override;
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StatusOr<HloInstruction*> ExpandInstruction(
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HloInstruction* gather_inst) override;
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private:
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Mode mode_;
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};
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} // namespace xla
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#endif // XLA_SERVICE_GATHER_EXPANDER_H_
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