1// Copyright (c) 2018 Google LLC.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#ifndef SOURCE_OPT_LOOP_FISSION_H_
16#define SOURCE_OPT_LOOP_FISSION_H_
17
18#include <algorithm>
19#include <cstdint>
20#include <map>
21#include <utility>
22#include <vector>
23
24#include "source/opt/cfg.h"
25#include "source/opt/loop_dependence.h"
26#include "source/opt/loop_utils.h"
27#include "source/opt/module.h"
28#include "source/opt/pass.h"
29#include "source/opt/tree_iterator.h"
30
31namespace spvtools {
32namespace opt {
33
34class LoopFissionPass : public Pass {
35 public:
36 // Fuction used to determine if a given loop should be split. Takes register
37 // pressure region for that loop as a parameter and returns true if the loop
38 // should be split.
39 using FissionCriteriaFunction =
40 std::function<bool(const RegisterLiveness::RegionRegisterLiveness&)>;
41
42 // Pass built with this constructor will split all loops regardless of
43 // register pressure. Will not split loops more than once.
44 LoopFissionPass();
45
46 // Split the loop if the number of registers used in the loop exceeds
47 // |register_threshold_to_split|. |split_multiple_times| flag determines
48 // whether or not the pass should split loops after already splitting them
49 // once.
50 LoopFissionPass(size_t register_threshold_to_split,
51 bool split_multiple_times = true);
52
53 // Split loops whose register pressure meets the criteria of |functor|.
54 LoopFissionPass(FissionCriteriaFunction functor,
55 bool split_multiple_times = true)
56 : split_criteria_(functor), split_multiple_times_(split_multiple_times) {}
57
58 const char* name() const override { return "loop-fission"; }
59
60 Pass::Status Process() override;
61
62 // Checks if |loop| meets the register pressure criteria to be split.
63 bool ShouldSplitLoop(const Loop& loop, IRContext* context);
64
65 private:
66 // Functor to run in ShouldSplitLoop to determine if the register pressure
67 // criteria is met for splitting the loop.
68 FissionCriteriaFunction split_criteria_;
69
70 // Flag designating whether or not we should also split the result of
71 // previously split loops if they meet the register presure criteria.
72 bool split_multiple_times_;
73};
74
75} // namespace opt
76} // namespace spvtools
77
78#endif // SOURCE_OPT_LOOP_FISSION_H_
79