1// Copyright (c) 2017 Google Inc.
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_PRIVATE_TO_LOCAL_PASS_H_
16#define SOURCE_OPT_PRIVATE_TO_LOCAL_PASS_H_
17
18#include "source/opt/ir_context.h"
19#include "source/opt/pass.h"
20
21namespace spvtools {
22namespace opt {
23
24// This pass implements total redundancy elimination. This is the same as
25// local redundancy elimination except it looks across basic block boundaries.
26// An instruction, inst, is totally redundant if there is another instruction
27// that dominates inst, and also computes the same value.
28class PrivateToLocalPass : public Pass {
29 public:
30 const char* name() const override { return "private-to-local"; }
31 Status Process() override;
32
33 IRContext::Analysis GetPreservedAnalyses() override {
34 return IRContext::kAnalysisDefUse |
35 IRContext::kAnalysisInstrToBlockMapping |
36 IRContext::kAnalysisDecorations | IRContext::kAnalysisCombinators |
37 IRContext::kAnalysisCFG | IRContext::kAnalysisDominatorAnalysis |
38 IRContext::kAnalysisNameMap | IRContext::kAnalysisConstants |
39 IRContext::kAnalysisTypes;
40 }
41
42 private:
43 // Moves |variable| from the private storage class to the function storage
44 // class of |function|. Returns false if the variable could not be moved.
45 bool MoveVariable(Instruction* variable, Function* function);
46
47 // |inst| is an instruction declaring a varible. If that variable is
48 // referenced in a single function and all of uses are valid as defined by
49 // |IsValidUse|, then that function is returned. Otherwise, the return
50 // value is |nullptr|.
51 Function* FindLocalFunction(const Instruction& inst) const;
52
53 // Returns true is |inst| is a valid use of a pointer. In this case, a
54 // valid use is one where the transformation is able to rewrite the type to
55 // match a change in storage class of the original variable.
56 bool IsValidUse(const Instruction* inst) const;
57
58 // Given the result id of a pointer type, |old_type_id|, this function
59 // returns the id of a the same pointer type except the storage class has
60 // been changed to function. If the type does not already exist, it will be
61 // created. Returns 0 if the new type could not be found or generated.
62 uint32_t GetNewType(uint32_t old_type_id);
63
64 // Updates |inst|, and any instruction dependent on |inst|, to reflect the
65 // change of the base pointer now pointing to the function storage class.
66 bool UpdateUse(Instruction* inst);
67 bool UpdateUses(uint32_t id);
68};
69
70} // namespace opt
71} // namespace spvtools
72
73#endif // SOURCE_OPT_PRIVATE_TO_LOCAL_PASS_H_
74