1 /*
2 * Copyright (c) 1998, 2005, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
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).
14 *
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,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 // This file defines the IndexSet class, a set of sparse integer indices.
26 // This data structure is used by the compiler in its liveness analysis and
27 // during register allocation.
28
29 //-------------------------------- class IndexSet ----------------------------
30 // An IndexSet is a piece-wise bitvector. At the top level, we have an array
31 // of pointers to bitvector chunks called BitBlocks. Each BitBlock has a fixed
32 // size and is allocated from a shared free list. The bits which are set in
33 // each BitBlock correspond to the elements of the set.
34
35 class IndexSet : public ResourceObj {
36 friend class IndexSetIterator;
37
38 public:
39 // When we allocate an IndexSet, it starts off with an array of top level block
40 // pointers of a set length. This size is intended to be large enough for the
41 // majority of IndexSets. In the cases when this size is not large enough,
42 // a separately allocated array is used.
43
44 // The length of the preallocated top level block array
45 enum { preallocated_block_list_size = 16 };
46
47 // Elements of a IndexSet get decomposed into three fields. The highest order
48 // bits are the block index, which tell which high level block holds the element.
49 // Within that block, the word index indicates which word holds the element.
50 // Finally, the bit index determines which single bit within that word indicates
51 // membership of the element in the set.
52
53 // The lengths of the index bitfields
54 enum { bit_index_length = 5,
55 word_index_length = 3,
56 block_index_length = 8 // not used
57 };
58
59 // Derived constants used for manipulating the index bitfields
60 enum {
61 bit_index_offset = 0, // not used
62 word_index_offset = bit_index_length,
63 block_index_offset = bit_index_length + word_index_length,
64
65 bits_per_word = 1 << bit_index_length,
66 words_per_block = 1 << word_index_length,
67 bits_per_block = bits_per_word * words_per_block,
68
69 bit_index_mask = right_n_bits(bit_index_length),
70 word_index_mask = right_n_bits(word_index_length)
71 };
72
73 // These routines are used for extracting the block, word, and bit index
74 // from an element.
75 static uint get_block_index(uint element) {
76 return element >> block_index_offset;
77 }
78 static uint get_word_index(uint element) {
79 return mask_bits(element >> word_index_offset,word_index_mask);
80 }
81 static uint get_bit_index(uint element) {
82 return mask_bits(element,bit_index_mask);
83 }
84
85 //------------------------------ class BitBlock ----------------------------
86 // The BitBlock class is a segment of a bitvector set.
87
88 class BitBlock : public ResourceObj {
89 friend class IndexSetIterator;
90 friend class IndexSet;
91
92 private:
93 // All of BitBlocks fields and methods are declared private. We limit
94 // access to IndexSet and IndexSetIterator.
95
96 // A BitBlock is composed of some number of 32 bit words. When a BitBlock
97 // is not in use by any IndexSet, it is stored on a free list. The next field
98 // is used by IndexSet to mainting this free list.
99
100 union {
101 uint32 _words[words_per_block];
102 BitBlock *_next;
103 } _data;
104
105 // accessors
106 uint32 *words() { return _data._words; }
107 void set_next(BitBlock *next) { _data._next = next; }
108 BitBlock *next() { return _data._next; }
109
110 // Operations. A BitBlock supports four simple operations,
111 // clear(), member(), insert(), and remove(). These methods do
112 // not assume that the block index has been masked out.
113
114 void clear() {
115 memset(words(), 0, sizeof(uint32) * words_per_block);
116 }
117
118 bool member(uint element) {
119 uint word_index = IndexSet::get_word_index(element);
120 uint bit_index = IndexSet::get_bit_index(element);
121
122 return ((words()[word_index] & (uint32)(0x1 << bit_index)) != 0);
123 }
124
125 bool insert(uint element) {
126 uint word_index = IndexSet::get_word_index(element);
127 uint bit_index = IndexSet::get_bit_index(element);
128
129 uint32 bit = (0x1 << bit_index);
130 uint32 before = words()[word_index];
131 words()[word_index] = before | bit;
132 return ((before & bit) != 0);
133 }
134
135 bool remove(uint element) {
136 uint word_index = IndexSet::get_word_index(element);
137 uint bit_index = IndexSet::get_bit_index(element);
138
139 uint32 bit = (0x1 << bit_index);
140 uint32 before = words()[word_index];
141 words()[word_index] = before & ~bit;
142 return ((before & bit) != 0);
143 }
144 };
145
146 //-------------------------- BitBlock allocation ---------------------------
147 private:
148
149 // All IndexSets share an arena from which they allocate BitBlocks. Unused
150 // BitBlocks are placed on a free list.
151
152 // The number of BitBlocks to allocate at a time
153 enum { bitblock_alloc_chunk_size = 50 };
154
155 static Arena *arena() { return Compile::current()->indexSet_arena(); }
156
157 static void populate_free_list();
158
159 public:
160
161 // Invalidate the current free BitBlock list and begin allocation
162 // from a new arena. It is essential that this method is called whenever
163 // the Arena being used for BitBlock allocation is reset.
164 static void reset_memory(Compile* compile, Arena *arena) {
165 compile->set_indexSet_free_block_list(NULL);
166 compile->set_indexSet_arena(arena);
167
168 // This should probably be done in a static initializer
169 _empty_block.clear();
170 }
171
172 private:
173 friend class BitBlock;
174 // A distinguished BitBlock which always remains empty. When a new IndexSet is
175 // created, all of its top level BitBlock pointers are initialized to point to
176 // this.
177 static BitBlock _empty_block;
178
179 //-------------------------- Members ------------------------------------------
180
181 // The number of elements in the set
182 uint _count;
183
184 // Our top level array of bitvector segments
185 BitBlock **_blocks;
186
187 BitBlock *_preallocated_block_list[preallocated_block_list_size];
188
189 // The number of top level array entries in use
190 uint _max_blocks;
191
192 // Our assertions need to know the maximum number allowed in the set
193 #ifdef ASSERT
194 uint _max_elements;
195 #endif
196
197 // The next IndexSet on the free list (not used at same time as count)
198 IndexSet *_next;
199
200 public:
201 //-------------------------- Free list operations ------------------------------
202 // Individual IndexSets can be placed on a free list. This is done in PhaseLive.
203
204 IndexSet *next() {
205 #ifdef ASSERT
206 if( VerifyOpto ) {
207 check_watch("removed from free list?", ((_next == NULL) ? 0 : _next->_serial_number));
208 }
209 #endif
210 return _next;
211 }
212
213 void set_next(IndexSet *next) {
214 #ifdef ASSERT
215 if( VerifyOpto ) {
216 check_watch("put on free list?", ((next == NULL) ? 0 : next->_serial_number));
217 }
218 #endif
219 _next = next;
220 }
221
222 private:
223 //-------------------------- Utility methods -----------------------------------
224
225 // Get the block which holds element
226 BitBlock *get_block_containing(uint element) const {
227 assert(element < _max_elements, "element out of bounds");
228 return _blocks[get_block_index(element)];
229 }
230
231 // Set a block in the top level array
232 void set_block(uint index, BitBlock *block) {
233 #ifdef ASSERT
234 if( VerifyOpto )
235 check_watch("set block", index);
236 #endif
237 _blocks[index] = block;
238 }
239
240 // Get a BitBlock from the free list
241 BitBlock *alloc_block();
242
243 // Get a BitBlock from the free list and place it in the top level array
244 BitBlock *alloc_block_containing(uint element);
245
246 // Free a block from the top level array, placing it on the free BitBlock list
247 void free_block(uint i);
248
249 public:
250 //-------------------------- Primitive set operations --------------------------
251
252 void clear() {
253 #ifdef ASSERT
254 if( VerifyOpto )
255 check_watch("clear");
256 #endif
257 _count = 0;
258 for (uint i = 0; i < _max_blocks; i++) {
259 BitBlock *block = _blocks[i];
260 if (block != &_empty_block) {
261 free_block(i);
262 }
263 }
264 }
265
266 uint count() const { return _count; }
267
268 bool is_empty() const { return _count == 0; }
269
270 bool member(uint element) const {
271 return get_block_containing(element)->member(element);
272 }
273
274 bool insert(uint element) {
275 #ifdef ASSERT
276 if( VerifyOpto )
277 check_watch("insert", element);
278 #endif
279 if (element == 0) {
280 return 0;
281 }
282 BitBlock *block = get_block_containing(element);
283 if (block == &_empty_block) {
284 block = alloc_block_containing(element);
285 }
286 bool present = block->insert(element);
287 if (!present) {
288 _count++;
289 }
290 return !present;
291 }
292
293 bool remove(uint element) {
294 #ifdef ASSERT
295 if( VerifyOpto )
296 check_watch("remove", element);
297 #endif
298
299 BitBlock *block = get_block_containing(element);
300 bool present = block->remove(element);
301 if (present) {
302 _count--;
303 }
304 return present;
305 }
306
307 //-------------------------- Compound set operations ------------------------
308 // Compute the union of all elements of one and two which interfere
309 // with the RegMask mask. If the degree of the union becomes
310 // exceeds fail_degree, the union bails out. The underlying set is
311 // cleared before the union is performed.
312 uint lrg_union(uint lr1, uint lr2,
313 const uint fail_degree,
314 const class PhaseIFG *ifg,
315 const RegMask &mask);
316
317
318 //------------------------- Construction, initialization -----------------------
319
320 IndexSet() {}
321
322 // This constructor is used for making a deep copy of a IndexSet.
323 IndexSet(IndexSet *set);
324
325 // Perform initialization on a IndexSet
326 void initialize(uint max_element);
327
328 // Initialize a IndexSet. If the top level BitBlock array needs to be
329 // allocated, do it from the proffered arena. BitBlocks are still allocated
330 // from the static Arena member.
331 void initialize(uint max_element, Arena *arena);
332
333 // Exchange two sets
334 void swap(IndexSet *set);
335
336 //-------------------------- Debugging and statistics --------------------------
337
338 #ifndef PRODUCT
339 // Output a IndexSet for debugging
340 void dump() const;
341 #endif
342
343 #ifdef ASSERT
344 void tally_iteration_statistics() const;
345
346 // BitBlock allocation statistics
347 static uint _alloc_new;
348 static uint _alloc_total;
349
350 // Block density statistics
351 static long _total_bits;
352 static long _total_used_blocks;
353 static long _total_unused_blocks;
354
355 // Sanity tests
356 void verify() const;
357
358 static int _serial_count;
359 int _serial_number;
360
361 // Check to see if the serial number of the current set is the one we're tracing.
362 // If it is, print a message.
363 void check_watch(const char *operation, uint operand) const {
364 if (IndexSetWatch != 0) {
365 if (IndexSetWatch == -1 || _serial_number == IndexSetWatch) {
366 tty->print_cr("IndexSet %d : %s ( %d )", _serial_number, operation, operand);
367 }
368 }
369 }
370 void check_watch(const char *operation) const {
371 if (IndexSetWatch != 0) {
372 if (IndexSetWatch == -1 || _serial_number == IndexSetWatch) {
373 tty->print_cr("IndexSet %d : %s", _serial_number, operation);
374 }
375 }
376 }
377
378 public:
379 static void print_statistics();
380
381 #endif
382 };
383
384
385 //-------------------------------- class IndexSetIterator --------------------
386 // An iterator for IndexSets.
387
388 class IndexSetIterator VALUE_OBJ_CLASS_SPEC {
389 friend class IndexSet;
390
391 public:
392
393 // We walk over the bits in a word in chunks of size window_size.
394 enum { window_size = 5,
395 window_mask = right_n_bits(window_size),
396 table_size = (1 << window_size) };
397
398 // For an integer of length window_size, what is the first set bit?
399 static const byte _first_bit[table_size];
400
401 // For an integer of length window_size, what is the second set bit?
402 static const byte _second_bit[table_size];
403
404 private:
405 // The current word we are inspecting
406 uint32 _current;
407
408 // What element number are we currently on?
409 uint _value;
410
411 // The index of the next word we will inspect
412 uint _next_word;
413
414 // A pointer to the contents of the current block
415 uint32 *_words;
416
417 // The index of the next block we will inspect
418 uint _next_block;
419
420 // A pointer to the blocks in our set
421 IndexSet::BitBlock **_blocks;
422
423 // The number of blocks in the set
424 uint _max_blocks;
425
426 // If the iterator was created from a non-const set, we replace
427 // non-canonical empty blocks with the _empty_block pointer. If
428 // _set is NULL, we do no replacement.
429 IndexSet *_set;
430
431 // Advance to the next non-empty word and return the next
432 // element in the set.
433 uint advance_and_next();
434
435
436 public:
437
438 // If an iterator is built from a constant set then empty blocks
439 // are not canonicalized.
440 IndexSetIterator(IndexSet *set);
441 IndexSetIterator(const IndexSet *set);
442
443 // Return the next element of the set. Return 0 when done.
444 uint next() {
445 uint current = _current;
446 if (current != 0) {
447 uint value = _value;
448 while (mask_bits(current,window_mask) == 0) {
449 current >>= window_size;
450 value += window_size;
451 }
452
453 uint advance = _second_bit[mask_bits(current,window_mask)];
454 _current = current >> advance;
455 _value = value + advance;
456 return value + _first_bit[mask_bits(current,window_mask)];
457 } else {
458 return advance_and_next();
459 }
460 }
461 };