75 lines
2.7 KiB
C++
75 lines
2.7 KiB
C++
/* Copyright 2017 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_RESHAPE_MOVER_H_
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#define XLA_SERVICE_RESHAPE_MOVER_H_
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#include "xla/service/hlo_pass_interface.h"
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namespace xla {
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// This pass sinks kReshape and kTranspose operations (known as "rearrange" ops)
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// down through elementwise ops:
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//
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// op(rearrange(x), rearrange(y)) => rearrange(op(x, y)).
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//
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// We also handle the case where one of the operands is not itself a rearrange
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// op but can be trivially rearranged. For example:
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//
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// op(rearrange(x), broadcast(scalar_y)) =>
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// rearrange(x, broadcast'(scalar_y)).
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//
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// This pass should be run to a fixed point. It also expects algsimp to be run
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// after each iteration.
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struct ReshapeMoverOptions {
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// On some platforms, it's cheap to do `reshape(broadcast(f32[n] x))`. The
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// reshape and broadcast can always be fused, and the index calculations are
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// not expensive. In such cases it can be beneficial for us to create these
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// reshapes eagerly, allowing us to get rid of more expensive ones.
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bool reshape_of_1d_broadcast_is_cheap = false;
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};
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class ReshapeMover : public HloModulePass {
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public:
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explicit ReshapeMover(
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const ReshapeMoverOptions& options = ReshapeMoverOptions{})
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: options_(options) {}
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absl::string_view name() const override { return "reshape-mover"; }
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using HloPassInterface::Run;
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StatusOr<bool> Run(
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HloModule* module,
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const absl::flat_hash_set<absl::string_view>& execution_threads) override;
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private:
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StatusOr<bool> TryReshapeMoveOnCandidates(HloInstructionSet* candidates);
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StatusOr<bool> SinkRearrangeOperands(HloInstruction* instruction);
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StatusOr<HloInstruction*> ApplyInverseRearrange(
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const HloInstruction* rearrange, HloInstruction* operand);
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bool IsReshapeMoveCandidate(HloInstruction* instruction);
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const HloInstruction* FirstNontrivialRearrange(
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absl::Span<const HloInstruction* const> instrs);
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bool CanTriviallyRearrange(const HloInstruction* instr,
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const HloInstruction* rearrange);
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ReshapeMoverOptions options_;
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};
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} // namespace xla
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#endif // XLA_SERVICE_RESHAPE_MOVER_H_
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