1 /*
2 * Copyright (c) 1998, 2010, 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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7 * published by the Free Software Foundation.
8 *
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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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15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
24
25 #ifndef SHARE_VM_COMPILER_METHODLIVENESS_HPP
26 #define SHARE_VM_COMPILER_METHODLIVENESS_HPP
27
28 #include "utilities/bitMap.hpp"
29 #include "utilities/growableArray.hpp"
30
31 class ciMethod;
32
33 class MethodLivenessResult : public BitMap {
34 private:
35 bool _is_valid;
36
37 public:
38 MethodLivenessResult(BitMap::bm_word_t* map, idx_t size_in_bits)
39 : BitMap(map, size_in_bits)
40 , _is_valid(false)
41 {}
42
43 MethodLivenessResult(idx_t size_in_bits)
44 : BitMap(size_in_bits)
45 , _is_valid(false)
46 {}
47
48 void set_is_valid() { _is_valid = true; }
49 bool is_valid() { return _is_valid; }
50 };
51
52 class MethodLiveness : public ResourceObj {
53 public:
54 // The BasicBlock class is used to represent a basic block in the
55 // liveness analysis.
56 class BasicBlock : public ResourceObj {
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 BitMap _entry;
70
71 // The summarized liveness effects of our direct successors reached
72 // by normal control flow
73 BitMap _normal_exit;
74
75 // The summarized liveness effects of our direct successors reached
76 // by exceptional control flow
77 BitMap _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 BitMap _gen;
84 BitMap _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(BitMap other);
104
105 // Our successors call this method to merge liveness information into
106 // our _exception_exit member.
107 bool merge_exception(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 int _bit_map_size_words;
185
186 // A list of all BasicBlocks.
187 BasicBlock **_block_list;
188
189 // number of blocks
190 int _block_count;
191
192 // Keeps track of bci->block mapping. One entry for each bci. Only block starts are
193 // recorded.
194 GrowableArray<BasicBlock*>* _block_map;
195
196 // Our work list.
197 BasicBlock *_work_list;
198
199 #ifdef COMPILER1
200 // bcis where blocks start are marked
201 BitMap _bci_block_start;
202 #endif // COMPILER1
203
204 // -- Graph construction & Analysis
205
206 // Compute ranges and predecessors for basic blocks.
207 void init_basic_blocks();
208
209 // Compute gen/kill information for all basic blocks.
210 void init_gen_kill();
211
212 // Perform the dataflow.
213 void propagate_liveness();
214
215 // The class MethodLiveness::BasicBlock needs special access to some
216 // of our members.
217 friend class MethodLiveness::BasicBlock;
218
219 // And accessors.
220 int bit_map_size_bits() const { return _bit_map_size_bits; }
221 int bit_map_size_words() const { return _bit_map_size_words; }
222
223 // Work list manipulation routines. Called internally by BasicBlock.
224 BasicBlock *work_list_get();
225 void work_list_add(BasicBlock *block);
226
227 // -- Timing and Statistics.
228
229
230 // Timers
231 static elapsedTimer _time_build_graph;
232 static elapsedTimer _time_gen_kill;
233 static elapsedTimer _time_flow;
234 static elapsedTimer _time_query;
235 static elapsedTimer _time_total;
236
237 #ifndef PRODUCT
238
239 // Counts
240 static long _total_bytes;
241 static int _total_methods;
242
243 static long _total_blocks;
244 static int _max_method_blocks;
245
246 static long _total_edges;
247 static int _max_block_edges;
248
249 static long _total_exc_edges;
250 static int _max_block_exc_edges;
251
252 static long _total_method_locals;
253 static int _max_method_locals;
254
255 static long _total_locals_queried;
256 static long _total_live_locals_queried;
257
258 static long _total_visits;
259
260 #endif
261
262 public:
263 // Create a liveness analyzer for a method
264 MethodLiveness(Arena* arena, ciMethod* method);
265
266 // Compute liveness information for the method
267 void compute_liveness();
268
269 // Find out which locals are live at a specific bci.
270 MethodLivenessResult get_liveness_at(int bci);
271
272 #ifdef COMPILER1
273 const BitMap get_bci_block_start() const { return _bci_block_start; }
274 #endif // COMPILER1
275
276 static void print_times() PRODUCT_RETURN;
277 };
278
279 #endif // SHARE_VM_COMPILER_METHODLIVENESS_HPP