1 /*
2 * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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24
25 #ifndef SHARE_COMPILER_METHODLIVENESS_HPP
26 #define SHARE_COMPILER_METHODLIVENESS_HPP
27
28 #include "utilities/bitMap.hpp"
29 #include "utilities/growableArray.hpp"
30
31 class ciMethod;
32
33 class MethodLivenessResult : public ResourceBitMap {
34 private:
35 bool _is_valid;
36
37 public:
38 MethodLivenessResult()
39 : ResourceBitMap()
40 , _is_valid(false)
41 {}
42
43 MethodLivenessResult(idx_t size_in_bits)
44 : ResourceBitMap(size_in_bits)
45 , _is_valid(false)
46 {}
47
48 void set_is_valid() { _is_valid = true; }
49 bool is_valid() const { return _is_valid; }
50 };
51
52 class MethodLiveness : public ArenaObj {
53 public:
54 // The BasicBlock class is used to represent a basic block in the
55 // liveness analysis.
56 class BasicBlock : public ArenaObj {
57 private:
58 // This class is only used by the MethodLiveness class.
59 friend class MethodLiveness;
60
61 // The analyzer which created this basic block.
62 MethodLiveness* _analyzer;
63
64 // The range of this basic block is [start_bci,limit_bci)
65 int _start_bci;
66 int _limit_bci;
67
68 // The liveness at the start of the block;
69 ArenaBitMap _entry;
70
71 // The summarized liveness effects of our direct successors reached
72 // by normal control flow
73 ArenaBitMap _normal_exit;
74
75 // The summarized liveness effects of our direct successors reached
76 // by exceptional control flow
77 ArenaBitMap _exception_exit;
78
79 // These members hold the results of the last call to
80 // compute_gen_kill_range(). _gen is the set of locals
81 // used before they are defined in the range. _kill is the
82 // set of locals defined before they are used.
83 ArenaBitMap _gen;
84 ArenaBitMap _kill;
85 int _last_bci;
86
87 // A list of all blocks which could come directly before this one
88 // in normal (non-exceptional) control flow. We propagate liveness
89 // information to these blocks.
90 GrowableArray<BasicBlock*>* _normal_predecessors;
91
92 // A list of all blocks which could come directly before this one
93 // in exceptional control flow.
94 GrowableArray<BasicBlock*>* _exception_predecessors;
95
96 // The following fields are used to manage a work list used in the
97 // dataflow.
98 BasicBlock *_next;
99 bool _on_work_list;
100
101 // Our successors call this method to merge liveness information into
102 // our _normal_exit member.
103 bool merge_normal(const BitMap& other);
104
105 // Our successors call this method to merge liveness information into
106 // our _exception_exit member.
107 bool merge_exception(const BitMap& other);
108
109 // This helper routine is used to help compute the gen/kill pair for
110 // the block. It is also used to answer queries.
111 void compute_gen_kill_range(ciBytecodeStream *bytes);
112
113 // Compute the gen/kill effect of a single instruction.
114 void compute_gen_kill_single(ciBytecodeStream *instruction);
115
116 // Helpers for compute_gen_kill_single.
117 void load_one(int local);
118 void load_two(int local);
119 void store_one(int local);
120 void store_two(int local);
121
122 BasicBlock(MethodLiveness *analyzer, int start, int limit);
123
124 // -- Accessors
125
126 int start_bci() const { return _start_bci; }
127
128 int limit_bci() const { return _limit_bci; }
129 void set_limit_bci(int limit) { _limit_bci = limit; }
130
131 BasicBlock *next() const { return _next; }
132 void set_next(BasicBlock *next) { _next = next; }
133
134 bool on_work_list() const { return _on_work_list; }
135 void set_on_work_list(bool val) { _on_work_list = val; }
136
137 // -- Flow graph construction.
138
139 // Add a basic block to our list of normal predecessors.
140 void add_normal_predecessor(BasicBlock *pred) {
141 _normal_predecessors->append_if_missing(pred);
142 }
143
144 // Add a basic block to our list of exceptional predecessors
145 void add_exception_predecessor(BasicBlock *pred) {
146 _exception_predecessors->append_if_missing(pred);
147 }
148
149 // Split the basic block at splitBci. This basic block
150 // becomes the second half. The first half is newly created.
151 BasicBlock *split(int splitBci);
152
153 // -- Dataflow.
154
155 void compute_gen_kill(ciMethod* method);
156
157 // Propagate changes from this basic block
158 void propagate(MethodLiveness *ml);
159
160 // -- Query.
161
162 MethodLivenessResult get_liveness_at(ciMethod* method, int bci);
163
164 // -- Debugging.
165
166 void print_on(outputStream *os) const PRODUCT_RETURN;
167
168 }; // End of MethodLiveness::BasicBlock
169
170 private:
171 // The method we are analyzing.
172 ciMethod* _method;
173 ciMethod* method() const { return _method; }
174
175 // The arena for storing structures...
176 Arena* _arena;
177 Arena* arena() const { return _arena; }
178
179 // We cache the length of the method.
180 int _code_size;
181
182 // The size of a BitMap.
183 int _bit_map_size_bits;
184
185 // A list of all BasicBlocks.
186 BasicBlock **_block_list;
187
188 // number of blocks
189 int _block_count;
190
191 // Keeps track of bci->block mapping. One entry for each bci. Only block starts are
192 // recorded.
193 GrowableArray<BasicBlock*>* _block_map;
194
195 // Our work list.
196 BasicBlock *_work_list;
197
198 #ifdef COMPILER1
199 // bcis where blocks start are marked
200 ArenaBitMap _bci_block_start;
201 #endif // COMPILER1
202
203 // -- Graph construction & Analysis
204
205 // Compute ranges and predecessors for basic blocks.
206 void init_basic_blocks();
207
208 // Compute gen/kill information for all basic blocks.
209 void init_gen_kill();
210
211 // Perform the dataflow.
212 void propagate_liveness();
213
214 // The class MethodLiveness::BasicBlock needs special access to some
215 // of our members.
216 friend class MethodLiveness::BasicBlock;
217
218 // And accessors.
219 int bit_map_size_bits() const { return _bit_map_size_bits; }
220
221 // Work list manipulation routines. Called internally by BasicBlock.
222 BasicBlock *work_list_get();
223 void work_list_add(BasicBlock *block);
224
225 public:
226 // Create a liveness analyzer for a method
227 MethodLiveness(Arena* arena, ciMethod* method);
228
229 // Compute liveness information for the method
230 void compute_liveness();
231
232 // Find out which locals are live at a specific bci.
233 MethodLivenessResult get_liveness_at(int bci);
234
235 #ifdef COMPILER1
236 const BitMap& get_bci_block_start() const { return _bci_block_start; }
237 #endif // COMPILER1
238
239 };
240
241 #endif // SHARE_COMPILER_METHODLIVENESS_HPP