1 /* "Bag-of-pages" garbage collector for the GNU compiler.
2 Copyright (C) 1999-2016 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "backend.h"
24 #include "alias.h"
25 #include "tree.h"
26 #include "rtl.h"
27 #include "tm_p.h"
28 #include "diagnostic-core.h"
29 #include "flags.h"
30 #include "ggc-internal.h"
31 #include "timevar.h"
32 #include "params.h"
33 #include "cgraph.h"
34 #include "cfgloop.h"
35 #include "plugin.h"
36
37 /* Prefer MAP_ANON(YMOUS) to /dev/zero, since we don't need to keep a
38 file open. Prefer either to valloc. */
39 #ifdef HAVE_MMAP_ANON
40 # undef HAVE_MMAP_DEV_ZERO
41 # define USING_MMAP
42 #endif
43
44 #ifdef HAVE_MMAP_DEV_ZERO
45 # define USING_MMAP
46 #endif
47
48 #ifndef USING_MMAP
49 #define USING_MALLOC_PAGE_GROUPS
50 #endif
51
52 #if defined(HAVE_MADVISE) && HAVE_DECL_MADVISE && defined(MADV_DONTNEED) \
53 && defined(USING_MMAP)
54 # define USING_MADVISE
55 #endif
56
57 /* Strategy:
58
59 This garbage-collecting allocator allocates objects on one of a set
60 of pages. Each page can allocate objects of a single size only;
61 available sizes are powers of two starting at four bytes. The size
62 of an allocation request is rounded up to the next power of two
63 (`order'), and satisfied from the appropriate page.
64
65 Each page is recorded in a page-entry, which also maintains an
66 in-use bitmap of object positions on the page. This allows the
67 allocation state of a particular object to be flipped without
68 touching the page itself.
69
70 Each page-entry also has a context depth, which is used to track
71 pushing and popping of allocation contexts. Only objects allocated
72 in the current (highest-numbered) context may be collected.
73
74 Page entries are arranged in an array of singly-linked lists. The
75 array is indexed by the allocation size, in bits, of the pages on
76 it; i.e. all pages on a list allocate objects of the same size.
77 Pages are ordered on the list such that all non-full pages precede
78 all full pages, with non-full pages arranged in order of decreasing
79 context depth.
80
81 Empty pages (of all orders) are kept on a single page cache list,
82 and are considered first when new pages are required; they are
83 deallocated at the start of the next collection if they haven't
84 been recycled by then. */
85
86 /* Define GGC_DEBUG_LEVEL to print debugging information.
87 0: No debugging output.
88 1: GC statistics only.
89 2: Page-entry allocations/deallocations as well.
90 3: Object allocations as well.
91 4: Object marks as well. */
92 #define GGC_DEBUG_LEVEL (0)
93
94 /* A two-level tree is used to look up the page-entry for a given
95 pointer. Two chunks of the pointer's bits are extracted to index
96 the first and second levels of the tree, as follows:
97
98 HOST_PAGE_SIZE_BITS
99 32 | |
100 msb +----------------+----+------+------+ lsb
101 | | |
102 PAGE_L1_BITS |
103 | |
104 PAGE_L2_BITS
105
106 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
107 pages are aligned on system page boundaries. The next most
108 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
109 index values in the lookup table, respectively.
110
111 For 32-bit architectures and the settings below, there are no
112 leftover bits. For architectures with wider pointers, the lookup
113 tree points to a list of pages, which must be scanned to find the
114 correct one. */
115
116 #define PAGE_L1_BITS (8)
117 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
118 #define PAGE_L1_SIZE ((uintptr_t) 1 << PAGE_L1_BITS)
119 #define PAGE_L2_SIZE ((uintptr_t) 1 << PAGE_L2_BITS)
120
121 #define LOOKUP_L1(p) \
122 (((uintptr_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
123
124 #define LOOKUP_L2(p) \
125 (((uintptr_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
126
127 /* The number of objects per allocation page, for objects on a page of
128 the indicated ORDER. */
129 #define OBJECTS_PER_PAGE(ORDER) objects_per_page_table[ORDER]
130
131 /* The number of objects in P. */
132 #define OBJECTS_IN_PAGE(P) ((P)->bytes / OBJECT_SIZE ((P)->order))
133
134 /* The size of an object on a page of the indicated ORDER. */
135 #define OBJECT_SIZE(ORDER) object_size_table[ORDER]
136
137 /* For speed, we avoid doing a general integer divide to locate the
138 offset in the allocation bitmap, by precalculating numbers M, S
139 such that (O * M) >> S == O / Z (modulo 2^32), for any offset O
140 within the page which is evenly divisible by the object size Z. */
141 #define DIV_MULT(ORDER) inverse_table[ORDER].mult
142 #define DIV_SHIFT(ORDER) inverse_table[ORDER].shift
143 #define OFFSET_TO_BIT(OFFSET, ORDER) \
144 (((OFFSET) * DIV_MULT (ORDER)) >> DIV_SHIFT (ORDER))
145
146 /* We use this structure to determine the alignment required for
147 allocations. For power-of-two sized allocations, that's not a
148 problem, but it does matter for odd-sized allocations.
149 We do not care about alignment for floating-point types. */
150
151 struct max_alignment {
152 char c;
153 union {
154 int64_t i;
155 void *p;
156 } u;
157 };
158
159 /* The biggest alignment required. */
160
161 #define MAX_ALIGNMENT (offsetof (struct max_alignment, u))
162
163
164 /* The number of extra orders, not corresponding to power-of-two sized
165 objects. */
166
167 #define NUM_EXTRA_ORDERS ARRAY_SIZE (extra_order_size_table)
168
169 #define RTL_SIZE(NSLOTS) \
170 (RTX_HDR_SIZE + (NSLOTS) * sizeof (rtunion))
171
172 #define TREE_EXP_SIZE(OPS) \
173 (sizeof (struct tree_exp) + ((OPS) - 1) * sizeof (tree))
174
175 /* The Ith entry is the maximum size of an object to be stored in the
176 Ith extra order. Adding a new entry to this array is the *only*
177 thing you need to do to add a new special allocation size. */
178
179 static const size_t extra_order_size_table[] = {
180 /* Extra orders for small non-power-of-two multiples of MAX_ALIGNMENT.
181 There are a lot of structures with these sizes and explicitly
182 listing them risks orders being dropped because they changed size. */
183 MAX_ALIGNMENT * 3,
184 MAX_ALIGNMENT * 5,
185 MAX_ALIGNMENT * 6,
186 MAX_ALIGNMENT * 7,
187 MAX_ALIGNMENT * 9,
188 MAX_ALIGNMENT * 10,
189 MAX_ALIGNMENT * 11,
190 MAX_ALIGNMENT * 12,
191 MAX_ALIGNMENT * 13,
192 MAX_ALIGNMENT * 14,
193 MAX_ALIGNMENT * 15,
194 sizeof (struct tree_decl_non_common),
195 sizeof (struct tree_field_decl),
196 sizeof (struct tree_parm_decl),
197 sizeof (struct tree_var_decl),
198 sizeof (struct tree_type_non_common),
199 sizeof (struct function),
200 sizeof (struct basic_block_def),
201 sizeof (struct cgraph_node),
202 sizeof (struct loop),
203 };
204
205 /* The total number of orders. */
206
207 #define NUM_ORDERS (HOST_BITS_PER_PTR + NUM_EXTRA_ORDERS)
208
209 /* Compute the smallest nonnegative number which when added to X gives
210 a multiple of F. */
211
212 #define ROUND_UP_VALUE(x, f) ((f) - 1 - ((f) - 1 + (x)) % (f))
213
214 /* Round X to next multiple of the page size */
215
216 #define PAGE_ALIGN(x) ROUND_UP ((x), G.pagesize)
217
218 /* The Ith entry is the number of objects on a page or order I. */
219
220 static unsigned objects_per_page_table[NUM_ORDERS];
221
222 /* The Ith entry is the size of an object on a page of order I. */
223
224 static size_t object_size_table[NUM_ORDERS];
225
226 /* The Ith entry is a pair of numbers (mult, shift) such that
227 ((k * mult) >> shift) mod 2^32 == (k / OBJECT_SIZE(I)) mod 2^32,
228 for all k evenly divisible by OBJECT_SIZE(I). */
229
230 static struct
231 {
232 size_t mult;
233 unsigned int shift;
234 }
235 inverse_table[NUM_ORDERS];
236
237 /* A page_entry records the status of an allocation page. This
238 structure is dynamically sized to fit the bitmap in_use_p. */
239 struct page_entry
240 {
241 /* The next page-entry with objects of the same size, or NULL if
242 this is the last page-entry. */
243 struct page_entry *next;
244
245 /* The previous page-entry with objects of the same size, or NULL if
246 this is the first page-entry. The PREV pointer exists solely to
247 keep the cost of ggc_free manageable. */
248 struct page_entry *prev;
249
250 /* The number of bytes allocated. (This will always be a multiple
251 of the host system page size.) */
252 size_t bytes;
253
254 /* The address at which the memory is allocated. */
255 char *page;
256
257 #ifdef USING_MALLOC_PAGE_GROUPS
258 /* Back pointer to the page group this page came from. */
259 struct page_group *group;
260 #endif
261
262 /* This is the index in the by_depth varray where this page table
263 can be found. */
264 unsigned long index_by_depth;
265
266 /* Context depth of this page. */
267 unsigned short context_depth;
268
269 /* The number of free objects remaining on this page. */
270 unsigned short num_free_objects;
271
272 /* A likely candidate for the bit position of a free object for the
273 next allocation from this page. */
274 unsigned short next_bit_hint;
275
276 /* The lg of size of objects allocated from this page. */
277 unsigned char order;
278
279 /* Discarded page? */
280 bool discarded;
281
282 /* A bit vector indicating whether or not objects are in use. The
283 Nth bit is one if the Nth object on this page is allocated. This
284 array is dynamically sized. */
285 unsigned long in_use_p[1];
286 };
287
288 #ifdef USING_MALLOC_PAGE_GROUPS
289 /* A page_group describes a large allocation from malloc, from which
290 we parcel out aligned pages. */
291 struct page_group
292 {
293 /* A linked list of all extant page groups. */
294 struct page_group *next;
295
296 /* The address we received from malloc. */
297 char *allocation;
298
299 /* The size of the block. */
300 size_t alloc_size;
301
302 /* A bitmask of pages in use. */
303 unsigned int in_use;
304 };
305 #endif
306
307 #if HOST_BITS_PER_PTR <= 32
308
309 /* On 32-bit hosts, we use a two level page table, as pictured above. */
310 typedef page_entry **page_table[PAGE_L1_SIZE];
311
312 #else
313
314 /* On 64-bit hosts, we use the same two level page tables plus a linked
315 list that disambiguates the top 32-bits. There will almost always be
316 exactly one entry in the list. */
317 typedef struct page_table_chain
318 {
319 struct page_table_chain *next;
320 size_t high_bits;
321 page_entry **table[PAGE_L1_SIZE];
322 } *page_table;
323
324 #endif
325
326 class finalizer
327 {
328 public:
finalizer(void * addr,void (* f)(void *))329 finalizer (void *addr, void (*f)(void *)) : m_addr (addr), m_function (f) {}
330
addr()331 void *addr () const { return m_addr; }
332
call()333 void call () const { m_function (m_addr); }
334
335 private:
336 void *m_addr;
337 void (*m_function)(void *);
338 };
339
340 class vec_finalizer
341 {
342 public:
vec_finalizer(uintptr_t addr,void (* f)(void *),size_t s,size_t n)343 vec_finalizer (uintptr_t addr, void (*f)(void *), size_t s, size_t n) :
344 m_addr (addr), m_function (f), m_object_size (s), m_n_objects (n) {}
345
call()346 void call () const
347 {
348 for (size_t i = 0; i < m_n_objects; i++)
349 m_function (reinterpret_cast<void *> (m_addr + (i * m_object_size)));
350 }
351
addr()352 void *addr () const { return reinterpret_cast<void *> (m_addr); }
353
354 private:
355 uintptr_t m_addr;
356 void (*m_function)(void *);
357 size_t m_object_size;
358 size_t m_n_objects;
359 };
360
361 #ifdef ENABLE_GC_ALWAYS_COLLECT
362 /* List of free objects to be verified as actually free on the
363 next collection. */
364 struct free_object
365 {
366 void *object;
367 struct free_object *next;
368 };
369 #endif
370
371 /* The rest of the global variables. */
372 static struct ggc_globals
373 {
374 /* The Nth element in this array is a page with objects of size 2^N.
375 If there are any pages with free objects, they will be at the
376 head of the list. NULL if there are no page-entries for this
377 object size. */
378 page_entry *pages[NUM_ORDERS];
379
380 /* The Nth element in this array is the last page with objects of
381 size 2^N. NULL if there are no page-entries for this object
382 size. */
383 page_entry *page_tails[NUM_ORDERS];
384
385 /* Lookup table for associating allocation pages with object addresses. */
386 page_table lookup;
387
388 /* The system's page size. */
389 size_t pagesize;
390 size_t lg_pagesize;
391
392 /* Bytes currently allocated. */
393 size_t allocated;
394
395 /* Bytes currently allocated at the end of the last collection. */
396 size_t allocated_last_gc;
397
398 /* Total amount of memory mapped. */
399 size_t bytes_mapped;
400
401 /* Bit N set if any allocations have been done at context depth N. */
402 unsigned long context_depth_allocations;
403
404 /* Bit N set if any collections have been done at context depth N. */
405 unsigned long context_depth_collections;
406
407 /* The current depth in the context stack. */
408 unsigned short context_depth;
409
410 /* A file descriptor open to /dev/zero for reading. */
411 #if defined (HAVE_MMAP_DEV_ZERO)
412 int dev_zero_fd;
413 #endif
414
415 /* A cache of free system pages. */
416 page_entry *free_pages;
417
418 #ifdef USING_MALLOC_PAGE_GROUPS
419 page_group *page_groups;
420 #endif
421
422 /* The file descriptor for debugging output. */
423 FILE *debug_file;
424
425 /* Current number of elements in use in depth below. */
426 unsigned int depth_in_use;
427
428 /* Maximum number of elements that can be used before resizing. */
429 unsigned int depth_max;
430
431 /* Each element of this array is an index in by_depth where the given
432 depth starts. This structure is indexed by that given depth we
433 are interested in. */
434 unsigned int *depth;
435
436 /* Current number of elements in use in by_depth below. */
437 unsigned int by_depth_in_use;
438
439 /* Maximum number of elements that can be used before resizing. */
440 unsigned int by_depth_max;
441
442 /* Each element of this array is a pointer to a page_entry, all
443 page_entries can be found in here by increasing depth.
444 index_by_depth in the page_entry is the index into this data
445 structure where that page_entry can be found. This is used to
446 speed up finding all page_entries at a particular depth. */
447 page_entry **by_depth;
448
449 /* Each element is a pointer to the saved in_use_p bits, if any,
450 zero otherwise. We allocate them all together, to enable a
451 better runtime data access pattern. */
452 unsigned long **save_in_use;
453
454 /* Finalizers for single objects. The first index is collection_depth. */
455 vec<vec<finalizer> > finalizers;
456
457 /* Finalizers for vectors of objects. */
458 vec<vec<vec_finalizer> > vec_finalizers;
459
460 #ifdef ENABLE_GC_ALWAYS_COLLECT
461 /* List of free objects to be verified as actually free on the
462 next collection. */
463 struct free_object *free_object_list;
464 #endif
465
466 struct
467 {
468 /* Total GC-allocated memory. */
469 unsigned long long total_allocated;
470 /* Total overhead for GC-allocated memory. */
471 unsigned long long total_overhead;
472
473 /* Total allocations and overhead for sizes less than 32, 64 and 128.
474 These sizes are interesting because they are typical cache line
475 sizes. */
476
477 unsigned long long total_allocated_under32;
478 unsigned long long total_overhead_under32;
479
480 unsigned long long total_allocated_under64;
481 unsigned long long total_overhead_under64;
482
483 unsigned long long total_allocated_under128;
484 unsigned long long total_overhead_under128;
485
486 /* The allocations for each of the allocation orders. */
487 unsigned long long total_allocated_per_order[NUM_ORDERS];
488
489 /* The overhead for each of the allocation orders. */
490 unsigned long long total_overhead_per_order[NUM_ORDERS];
491 } stats;
492 } G;
493
494 /* True if a gc is currently taking place. */
495
496 static bool in_gc = false;
497
498 /* The size in bytes required to maintain a bitmap for the objects
499 on a page-entry. */
500 #define BITMAP_SIZE(Num_objects) \
501 (CEIL ((Num_objects), HOST_BITS_PER_LONG) * sizeof (long))
502
503 /* Allocate pages in chunks of this size, to throttle calls to memory
504 allocation routines. The first page is used, the rest go onto the
505 free list. This cannot be larger than HOST_BITS_PER_INT for the
506 in_use bitmask for page_group. Hosts that need a different value
507 can override this by defining GGC_QUIRE_SIZE explicitly. */
508 #ifndef GGC_QUIRE_SIZE
509 # ifdef USING_MMAP
510 # define GGC_QUIRE_SIZE 512 /* 2MB for 4K pages */
511 # else
512 # define GGC_QUIRE_SIZE 16
513 # endif
514 #endif
515
516 /* Initial guess as to how many page table entries we might need. */
517 #define INITIAL_PTE_COUNT 128
518
519 static int ggc_allocated_p (const void *);
520 static page_entry *lookup_page_table_entry (const void *);
521 static void set_page_table_entry (void *, page_entry *);
522 #ifdef USING_MMAP
523 static char *alloc_anon (char *, size_t, bool check);
524 #endif
525 #ifdef USING_MALLOC_PAGE_GROUPS
526 static size_t page_group_index (char *, char *);
527 static void set_page_group_in_use (page_group *, char *);
528 static void clear_page_group_in_use (page_group *, char *);
529 #endif
530 static struct page_entry * alloc_page (unsigned);
531 static void free_page (struct page_entry *);
532 static void release_pages (void);
533 static void clear_marks (void);
534 static void sweep_pages (void);
535 static void ggc_recalculate_in_use_p (page_entry *);
536 static void compute_inverse (unsigned);
537 static inline void adjust_depth (void);
538 static void move_ptes_to_front (int, int);
539
540 void debug_print_page_list (int);
541 static void push_depth (unsigned int);
542 static void push_by_depth (page_entry *, unsigned long *);
543
544 /* Push an entry onto G.depth. */
545
546 inline static void
push_depth(unsigned int i)547 push_depth (unsigned int i)
548 {
549 if (G.depth_in_use >= G.depth_max)
550 {
551 G.depth_max *= 2;
552 G.depth = XRESIZEVEC (unsigned int, G.depth, G.depth_max);
553 }
554 G.depth[G.depth_in_use++] = i;
555 }
556
557 /* Push an entry onto G.by_depth and G.save_in_use. */
558
559 inline static void
push_by_depth(page_entry * p,unsigned long * s)560 push_by_depth (page_entry *p, unsigned long *s)
561 {
562 if (G.by_depth_in_use >= G.by_depth_max)
563 {
564 G.by_depth_max *= 2;
565 G.by_depth = XRESIZEVEC (page_entry *, G.by_depth, G.by_depth_max);
566 G.save_in_use = XRESIZEVEC (unsigned long *, G.save_in_use,
567 G.by_depth_max);
568 }
569 G.by_depth[G.by_depth_in_use] = p;
570 G.save_in_use[G.by_depth_in_use++] = s;
571 }
572
573 #if (GCC_VERSION < 3001)
574 #define prefetch(X) ((void) X)
575 #else
576 #define prefetch(X) __builtin_prefetch (X)
577 #endif
578
579 #define save_in_use_p_i(__i) \
580 (G.save_in_use[__i])
581 #define save_in_use_p(__p) \
582 (save_in_use_p_i (__p->index_by_depth))
583
584 /* Returns nonzero if P was allocated in GC'able memory. */
585
586 static inline int
ggc_allocated_p(const void * p)587 ggc_allocated_p (const void *p)
588 {
589 page_entry ***base;
590 size_t L1, L2;
591
592 #if HOST_BITS_PER_PTR <= 32
593 base = &G.lookup[0];
594 #else
595 page_table table = G.lookup;
596 uintptr_t high_bits = (uintptr_t) p & ~ (uintptr_t) 0xffffffff;
597 while (1)
598 {
599 if (table == NULL)
600 return 0;
601 if (table->high_bits == high_bits)
602 break;
603 table = table->next;
604 }
605 base = &table->table[0];
606 #endif
607
608 /* Extract the level 1 and 2 indices. */
609 L1 = LOOKUP_L1 (p);
610 L2 = LOOKUP_L2 (p);
611
612 return base[L1] && base[L1][L2];
613 }
614
615 /* Traverse the page table and find the entry for a page.
616 Die (probably) if the object wasn't allocated via GC. */
617
618 static inline page_entry *
lookup_page_table_entry(const void * p)619 lookup_page_table_entry (const void *p)
620 {
621 page_entry ***base;
622 size_t L1, L2;
623
624 #if HOST_BITS_PER_PTR <= 32
625 base = &G.lookup[0];
626 #else
627 page_table table = G.lookup;
628 uintptr_t high_bits = (uintptr_t) p & ~ (uintptr_t) 0xffffffff;
629 while (table->high_bits != high_bits)
630 table = table->next;
631 base = &table->table[0];
632 #endif
633
634 /* Extract the level 1 and 2 indices. */
635 L1 = LOOKUP_L1 (p);
636 L2 = LOOKUP_L2 (p);
637
638 return base[L1][L2];
639 }
640
641 /* Set the page table entry for a page. */
642
643 static void
set_page_table_entry(void * p,page_entry * entry)644 set_page_table_entry (void *p, page_entry *entry)
645 {
646 page_entry ***base;
647 size_t L1, L2;
648
649 #if HOST_BITS_PER_PTR <= 32
650 base = &G.lookup[0];
651 #else
652 page_table table;
653 uintptr_t high_bits = (uintptr_t) p & ~ (uintptr_t) 0xffffffff;
654 for (table = G.lookup; table; table = table->next)
655 if (table->high_bits == high_bits)
656 goto found;
657
658 /* Not found -- allocate a new table. */
659 table = XCNEW (struct page_table_chain);
660 table->next = G.lookup;
661 table->high_bits = high_bits;
662 G.lookup = table;
663 found:
664 base = &table->table[0];
665 #endif
666
667 /* Extract the level 1 and 2 indices. */
668 L1 = LOOKUP_L1 (p);
669 L2 = LOOKUP_L2 (p);
670
671 if (base[L1] == NULL)
672 base[L1] = XCNEWVEC (page_entry *, PAGE_L2_SIZE);
673
674 base[L1][L2] = entry;
675 }
676
677 /* Prints the page-entry for object size ORDER, for debugging. */
678
679 DEBUG_FUNCTION void
debug_print_page_list(int order)680 debug_print_page_list (int order)
681 {
682 page_entry *p;
683 printf ("Head=%p, Tail=%p:\n", (void *) G.pages[order],
684 (void *) G.page_tails[order]);
685 p = G.pages[order];
686 while (p != NULL)
687 {
688 printf ("%p(%1d|%3d) -> ", (void *) p, p->context_depth,
689 p->num_free_objects);
690 p = p->next;
691 }
692 printf ("NULL\n");
693 fflush (stdout);
694 }
695
696 #ifdef USING_MMAP
697 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
698 (if non-null). The ifdef structure here is intended to cause a
699 compile error unless exactly one of the HAVE_* is defined. */
700
701 static inline char *
alloc_anon(char * pref ATTRIBUTE_UNUSED,size_t size,bool check)702 alloc_anon (char *pref ATTRIBUTE_UNUSED, size_t size, bool check)
703 {
704 #ifdef HAVE_MMAP_ANON
705 char *page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
706 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
707 #endif
708 #ifdef HAVE_MMAP_DEV_ZERO
709 char *page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
710 MAP_PRIVATE, G.dev_zero_fd, 0);
711 #endif
712
713 if (page == (char *) MAP_FAILED)
714 {
715 if (!check)
716 return NULL;
717 perror ("virtual memory exhausted");
718 exit (FATAL_EXIT_CODE);
719 }
720
721 /* Remember that we allocated this memory. */
722 G.bytes_mapped += size;
723
724 /* Pretend we don't have access to the allocated pages. We'll enable
725 access to smaller pieces of the area in ggc_internal_alloc. Discard the
726 handle to avoid handle leak. */
727 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS (page, size));
728
729 return page;
730 }
731 #endif
732 #ifdef USING_MALLOC_PAGE_GROUPS
733 /* Compute the index for this page into the page group. */
734
735 static inline size_t
page_group_index(char * allocation,char * page)736 page_group_index (char *allocation, char *page)
737 {
738 return (size_t) (page - allocation) >> G.lg_pagesize;
739 }
740
741 /* Set and clear the in_use bit for this page in the page group. */
742
743 static inline void
set_page_group_in_use(page_group * group,char * page)744 set_page_group_in_use (page_group *group, char *page)
745 {
746 group->in_use |= 1 << page_group_index (group->allocation, page);
747 }
748
749 static inline void
clear_page_group_in_use(page_group * group,char * page)750 clear_page_group_in_use (page_group *group, char *page)
751 {
752 group->in_use &= ~(1 << page_group_index (group->allocation, page));
753 }
754 #endif
755
756 /* Allocate a new page for allocating objects of size 2^ORDER,
757 and return an entry for it. The entry is not added to the
758 appropriate page_table list. */
759
760 static inline struct page_entry *
alloc_page(unsigned order)761 alloc_page (unsigned order)
762 {
763 struct page_entry *entry, *p, **pp;
764 char *page;
765 size_t num_objects;
766 size_t bitmap_size;
767 size_t page_entry_size;
768 size_t entry_size;
769 #ifdef USING_MALLOC_PAGE_GROUPS
770 page_group *group;
771 #endif
772
773 num_objects = OBJECTS_PER_PAGE (order);
774 bitmap_size = BITMAP_SIZE (num_objects + 1);
775 page_entry_size = sizeof (page_entry) - sizeof (long) + bitmap_size;
776 entry_size = num_objects * OBJECT_SIZE (order);
777 if (entry_size < G.pagesize)
778 entry_size = G.pagesize;
779 entry_size = PAGE_ALIGN (entry_size);
780
781 entry = NULL;
782 page = NULL;
783
784 /* Check the list of free pages for one we can use. */
785 for (pp = &G.free_pages, p = *pp; p; pp = &p->next, p = *pp)
786 if (p->bytes == entry_size)
787 break;
788
789 if (p != NULL)
790 {
791 if (p->discarded)
792 G.bytes_mapped += p->bytes;
793 p->discarded = false;
794
795 /* Recycle the allocated memory from this page ... */
796 *pp = p->next;
797 page = p->page;
798
799 #ifdef USING_MALLOC_PAGE_GROUPS
800 group = p->group;
801 #endif
802
803 /* ... and, if possible, the page entry itself. */
804 if (p->order == order)
805 {
806 entry = p;
807 memset (entry, 0, page_entry_size);
808 }
809 else
810 free (p);
811 }
812 #ifdef USING_MMAP
813 else if (entry_size == G.pagesize)
814 {
815 /* We want just one page. Allocate a bunch of them and put the
816 extras on the freelist. (Can only do this optimization with
817 mmap for backing store.) */
818 struct page_entry *e, *f = G.free_pages;
819 int i, entries = GGC_QUIRE_SIZE;
820
821 page = alloc_anon (NULL, G.pagesize * GGC_QUIRE_SIZE, false);
822 if (page == NULL)
823 {
824 page = alloc_anon (NULL, G.pagesize, true);
825 entries = 1;
826 }
827
828 /* This loop counts down so that the chain will be in ascending
829 memory order. */
830 for (i = entries - 1; i >= 1; i--)
831 {
832 e = XCNEWVAR (struct page_entry, page_entry_size);
833 e->order = order;
834 e->bytes = G.pagesize;
835 e->page = page + (i << G.lg_pagesize);
836 e->next = f;
837 f = e;
838 }
839
840 G.free_pages = f;
841 }
842 else
843 page = alloc_anon (NULL, entry_size, true);
844 #endif
845 #ifdef USING_MALLOC_PAGE_GROUPS
846 else
847 {
848 /* Allocate a large block of memory and serve out the aligned
849 pages therein. This results in much less memory wastage
850 than the traditional implementation of valloc. */
851
852 char *allocation, *a, *enda;
853 size_t alloc_size, head_slop, tail_slop;
854 int multiple_pages = (entry_size == G.pagesize);
855
856 if (multiple_pages)
857 alloc_size = GGC_QUIRE_SIZE * G.pagesize;
858 else
859 alloc_size = entry_size + G.pagesize - 1;
860 allocation = XNEWVEC (char, alloc_size);
861
862 page = (char *) (((uintptr_t) allocation + G.pagesize - 1) & -G.pagesize);
863 head_slop = page - allocation;
864 if (multiple_pages)
865 tail_slop = ((size_t) allocation + alloc_size) & (G.pagesize - 1);
866 else
867 tail_slop = alloc_size - entry_size - head_slop;
868 enda = allocation + alloc_size - tail_slop;
869
870 /* We allocated N pages, which are likely not aligned, leaving
871 us with N-1 usable pages. We plan to place the page_group
872 structure somewhere in the slop. */
873 if (head_slop >= sizeof (page_group))
874 group = (page_group *)page - 1;
875 else
876 {
877 /* We magically got an aligned allocation. Too bad, we have
878 to waste a page anyway. */
879 if (tail_slop == 0)
880 {
881 enda -= G.pagesize;
882 tail_slop += G.pagesize;
883 }
884 gcc_assert (tail_slop >= sizeof (page_group));
885 group = (page_group *)enda;
886 tail_slop -= sizeof (page_group);
887 }
888
889 /* Remember that we allocated this memory. */
890 group->next = G.page_groups;
891 group->allocation = allocation;
892 group->alloc_size = alloc_size;
893 group->in_use = 0;
894 G.page_groups = group;
895 G.bytes_mapped += alloc_size;
896
897 /* If we allocated multiple pages, put the rest on the free list. */
898 if (multiple_pages)
899 {
900 struct page_entry *e, *f = G.free_pages;
901 for (a = enda - G.pagesize; a != page; a -= G.pagesize)
902 {
903 e = XCNEWVAR (struct page_entry, page_entry_size);
904 e->order = order;
905 e->bytes = G.pagesize;
906 e->page = a;
907 e->group = group;
908 e->next = f;
909 f = e;
910 }
911 G.free_pages = f;
912 }
913 }
914 #endif
915
916 if (entry == NULL)
917 entry = XCNEWVAR (struct page_entry, page_entry_size);
918
919 entry->bytes = entry_size;
920 entry->page = page;
921 entry->context_depth = G.context_depth;
922 entry->order = order;
923 entry->num_free_objects = num_objects;
924 entry->next_bit_hint = 1;
925
926 G.context_depth_allocations |= (unsigned long)1 << G.context_depth;
927
928 #ifdef USING_MALLOC_PAGE_GROUPS
929 entry->group = group;
930 set_page_group_in_use (group, page);
931 #endif
932
933 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
934 increment the hint. */
935 entry->in_use_p[num_objects / HOST_BITS_PER_LONG]
936 = (unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG);
937
938 set_page_table_entry (page, entry);
939
940 if (GGC_DEBUG_LEVEL >= 2)
941 fprintf (G.debug_file,
942 "Allocating page at %p, object size=%lu, data %p-%p\n",
943 (void *) entry, (unsigned long) OBJECT_SIZE (order), page,
944 page + entry_size - 1);
945
946 return entry;
947 }
948
949 /* Adjust the size of G.depth so that no index greater than the one
950 used by the top of the G.by_depth is used. */
951
952 static inline void
adjust_depth(void)953 adjust_depth (void)
954 {
955 page_entry *top;
956
957 if (G.by_depth_in_use)
958 {
959 top = G.by_depth[G.by_depth_in_use-1];
960
961 /* Peel back indices in depth that index into by_depth, so that
962 as new elements are added to by_depth, we note the indices
963 of those elements, if they are for new context depths. */
964 while (G.depth_in_use > (size_t)top->context_depth+1)
965 --G.depth_in_use;
966 }
967 }
968
969 /* For a page that is no longer needed, put it on the free page list. */
970
971 static void
free_page(page_entry * entry)972 free_page (page_entry *entry)
973 {
974 if (GGC_DEBUG_LEVEL >= 2)
975 fprintf (G.debug_file,
976 "Deallocating page at %p, data %p-%p\n", (void *) entry,
977 entry->page, entry->page + entry->bytes - 1);
978
979 /* Mark the page as inaccessible. Discard the handle to avoid handle
980 leak. */
981 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS (entry->page, entry->bytes));
982
983 set_page_table_entry (entry->page, NULL);
984
985 #ifdef USING_MALLOC_PAGE_GROUPS
986 clear_page_group_in_use (entry->group, entry->page);
987 #endif
988
989 if (G.by_depth_in_use > 1)
990 {
991 page_entry *top = G.by_depth[G.by_depth_in_use-1];
992 int i = entry->index_by_depth;
993
994 /* We cannot free a page from a context deeper than the current
995 one. */
996 gcc_assert (entry->context_depth == top->context_depth);
997
998 /* Put top element into freed slot. */
999 G.by_depth[i] = top;
1000 G.save_in_use[i] = G.save_in_use[G.by_depth_in_use-1];
1001 top->index_by_depth = i;
1002 }
1003 --G.by_depth_in_use;
1004
1005 adjust_depth ();
1006
1007 entry->next = G.free_pages;
1008 G.free_pages = entry;
1009 }
1010
1011 /* Release the free page cache to the system. */
1012
1013 static void
release_pages(void)1014 release_pages (void)
1015 {
1016 #ifdef USING_MADVISE
1017 page_entry *p, *start_p;
1018 char *start;
1019 size_t len;
1020 size_t mapped_len;
1021 page_entry *next, *prev, *newprev;
1022 size_t free_unit = (GGC_QUIRE_SIZE/2) * G.pagesize;
1023
1024 /* First free larger continuous areas to the OS.
1025 This allows other allocators to grab these areas if needed.
1026 This is only done on larger chunks to avoid fragmentation.
1027 This does not always work because the free_pages list is only
1028 approximately sorted. */
1029
1030 p = G.free_pages;
1031 prev = NULL;
1032 while (p)
1033 {
1034 start = p->page;
1035 start_p = p;
1036 len = 0;
1037 mapped_len = 0;
1038 newprev = prev;
1039 while (p && p->page == start + len)
1040 {
1041 len += p->bytes;
1042 if (!p->discarded)
1043 mapped_len += p->bytes;
1044 newprev = p;
1045 p = p->next;
1046 }
1047 if (len >= free_unit)
1048 {
1049 while (start_p != p)
1050 {
1051 next = start_p->next;
1052 free (start_p);
1053 start_p = next;
1054 }
1055 munmap (start, len);
1056 if (prev)
1057 prev->next = p;
1058 else
1059 G.free_pages = p;
1060 G.bytes_mapped -= mapped_len;
1061 continue;
1062 }
1063 prev = newprev;
1064 }
1065
1066 /* Now give back the fragmented pages to the OS, but keep the address
1067 space to reuse it next time. */
1068
1069 for (p = G.free_pages; p; )
1070 {
1071 if (p->discarded)
1072 {
1073 p = p->next;
1074 continue;
1075 }
1076 start = p->page;
1077 len = p->bytes;
1078 start_p = p;
1079 p = p->next;
1080 while (p && p->page == start + len)
1081 {
1082 len += p->bytes;
1083 p = p->next;
1084 }
1085 /* Give the page back to the kernel, but don't free the mapping.
1086 This avoids fragmentation in the virtual memory map of the
1087 process. Next time we can reuse it by just touching it. */
1088 madvise (start, len, MADV_DONTNEED);
1089 /* Don't count those pages as mapped to not touch the garbage collector
1090 unnecessarily. */
1091 G.bytes_mapped -= len;
1092 while (start_p != p)
1093 {
1094 start_p->discarded = true;
1095 start_p = start_p->next;
1096 }
1097 }
1098 #endif
1099 #if defined(USING_MMAP) && !defined(USING_MADVISE)
1100 page_entry *p, *next;
1101 char *start;
1102 size_t len;
1103
1104 /* Gather up adjacent pages so they are unmapped together. */
1105 p = G.free_pages;
1106
1107 while (p)
1108 {
1109 start = p->page;
1110 next = p->next;
1111 len = p->bytes;
1112 free (p);
1113 p = next;
1114
1115 while (p && p->page == start + len)
1116 {
1117 next = p->next;
1118 len += p->bytes;
1119 free (p);
1120 p = next;
1121 }
1122
1123 munmap (start, len);
1124 G.bytes_mapped -= len;
1125 }
1126
1127 G.free_pages = NULL;
1128 #endif
1129 #ifdef USING_MALLOC_PAGE_GROUPS
1130 page_entry **pp, *p;
1131 page_group **gp, *g;
1132
1133 /* Remove all pages from free page groups from the list. */
1134 pp = &G.free_pages;
1135 while ((p = *pp) != NULL)
1136 if (p->group->in_use == 0)
1137 {
1138 *pp = p->next;
1139 free (p);
1140 }
1141 else
1142 pp = &p->next;
1143
1144 /* Remove all free page groups, and release the storage. */
1145 gp = &G.page_groups;
1146 while ((g = *gp) != NULL)
1147 if (g->in_use == 0)
1148 {
1149 *gp = g->next;
1150 G.bytes_mapped -= g->alloc_size;
1151 free (g->allocation);
1152 }
1153 else
1154 gp = &g->next;
1155 #endif
1156 }
1157
1158 /* This table provides a fast way to determine ceil(log_2(size)) for
1159 allocation requests. The minimum allocation size is eight bytes. */
1160 #define NUM_SIZE_LOOKUP 512
1161 static unsigned char size_lookup[NUM_SIZE_LOOKUP] =
1162 {
1163 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
1164 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
1165 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1166 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1167 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1168 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1169 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1170 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1171 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1172 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1173 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1174 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1175 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1176 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1177 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1178 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1179 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1180 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1181 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1182 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1183 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1184 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1185 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1186 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1187 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1188 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1189 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1190 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1191 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1192 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1193 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1194 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9
1195 };
1196
1197 /* For a given size of memory requested for allocation, return the
1198 actual size that is going to be allocated, as well as the size
1199 order. */
1200
1201 static void
ggc_round_alloc_size_1(size_t requested_size,size_t * size_order,size_t * alloced_size)1202 ggc_round_alloc_size_1 (size_t requested_size,
1203 size_t *size_order,
1204 size_t *alloced_size)
1205 {
1206 size_t order, object_size;
1207
1208 if (requested_size < NUM_SIZE_LOOKUP)
1209 {
1210 order = size_lookup[requested_size];
1211 object_size = OBJECT_SIZE (order);
1212 }
1213 else
1214 {
1215 order = 10;
1216 while (requested_size > (object_size = OBJECT_SIZE (order)))
1217 order++;
1218 }
1219
1220 if (size_order)
1221 *size_order = order;
1222 if (alloced_size)
1223 *alloced_size = object_size;
1224 }
1225
1226 /* For a given size of memory requested for allocation, return the
1227 actual size that is going to be allocated. */
1228
1229 size_t
ggc_round_alloc_size(size_t requested_size)1230 ggc_round_alloc_size (size_t requested_size)
1231 {
1232 size_t size = 0;
1233
1234 ggc_round_alloc_size_1 (requested_size, NULL, &size);
1235 return size;
1236 }
1237
1238 /* Push a finalizer onto the appropriate vec. */
1239
1240 static void
add_finalizer(void * result,void (* f)(void *),size_t s,size_t n)1241 add_finalizer (void *result, void (*f)(void *), size_t s, size_t n)
1242 {
1243 if (f == NULL)
1244 /* No finalizer. */;
1245 else if (n == 1)
1246 {
1247 finalizer fin (result, f);
1248 G.finalizers[G.context_depth].safe_push (fin);
1249 }
1250 else
1251 {
1252 vec_finalizer fin (reinterpret_cast<uintptr_t> (result), f, s, n);
1253 G.vec_finalizers[G.context_depth].safe_push (fin);
1254 }
1255 }
1256
1257 /* Allocate a chunk of memory of SIZE bytes. Its contents are undefined. */
1258
1259 void *
ggc_internal_alloc(size_t size,void (* f)(void *),size_t s,size_t n MEM_STAT_DECL)1260 ggc_internal_alloc (size_t size, void (*f)(void *), size_t s, size_t n
1261 MEM_STAT_DECL)
1262 {
1263 size_t order, word, bit, object_offset, object_size;
1264 struct page_entry *entry;
1265 void *result;
1266
1267 ggc_round_alloc_size_1 (size, &order, &object_size);
1268
1269 /* If there are non-full pages for this size allocation, they are at
1270 the head of the list. */
1271 entry = G.pages[order];
1272
1273 /* If there is no page for this object size, or all pages in this
1274 context are full, allocate a new page. */
1275 if (entry == NULL || entry->num_free_objects == 0)
1276 {
1277 struct page_entry *new_entry;
1278 new_entry = alloc_page (order);
1279
1280 new_entry->index_by_depth = G.by_depth_in_use;
1281 push_by_depth (new_entry, 0);
1282
1283 /* We can skip context depths, if we do, make sure we go all the
1284 way to the new depth. */
1285 while (new_entry->context_depth >= G.depth_in_use)
1286 push_depth (G.by_depth_in_use-1);
1287
1288 /* If this is the only entry, it's also the tail. If it is not
1289 the only entry, then we must update the PREV pointer of the
1290 ENTRY (G.pages[order]) to point to our new page entry. */
1291 if (entry == NULL)
1292 G.page_tails[order] = new_entry;
1293 else
1294 entry->prev = new_entry;
1295
1296 /* Put new pages at the head of the page list. By definition the
1297 entry at the head of the list always has a NULL pointer. */
1298 new_entry->next = entry;
1299 new_entry->prev = NULL;
1300 entry = new_entry;
1301 G.pages[order] = new_entry;
1302
1303 /* For a new page, we know the word and bit positions (in the
1304 in_use bitmap) of the first available object -- they're zero. */
1305 new_entry->next_bit_hint = 1;
1306 word = 0;
1307 bit = 0;
1308 object_offset = 0;
1309 }
1310 else
1311 {
1312 /* First try to use the hint left from the previous allocation
1313 to locate a clear bit in the in-use bitmap. We've made sure
1314 that the one-past-the-end bit is always set, so if the hint
1315 has run over, this test will fail. */
1316 unsigned hint = entry->next_bit_hint;
1317 word = hint / HOST_BITS_PER_LONG;
1318 bit = hint % HOST_BITS_PER_LONG;
1319
1320 /* If the hint didn't work, scan the bitmap from the beginning. */
1321 if ((entry->in_use_p[word] >> bit) & 1)
1322 {
1323 word = bit = 0;
1324 while (~entry->in_use_p[word] == 0)
1325 ++word;
1326
1327 #if GCC_VERSION >= 3004
1328 bit = __builtin_ctzl (~entry->in_use_p[word]);
1329 #else
1330 while ((entry->in_use_p[word] >> bit) & 1)
1331 ++bit;
1332 #endif
1333
1334 hint = word * HOST_BITS_PER_LONG + bit;
1335 }
1336
1337 /* Next time, try the next bit. */
1338 entry->next_bit_hint = hint + 1;
1339
1340 object_offset = hint * object_size;
1341 }
1342
1343 /* Set the in-use bit. */
1344 entry->in_use_p[word] |= ((unsigned long) 1 << bit);
1345
1346 /* Keep a running total of the number of free objects. If this page
1347 fills up, we may have to move it to the end of the list if the
1348 next page isn't full. If the next page is full, all subsequent
1349 pages are full, so there's no need to move it. */
1350 if (--entry->num_free_objects == 0
1351 && entry->next != NULL
1352 && entry->next->num_free_objects > 0)
1353 {
1354 /* We have a new head for the list. */
1355 G.pages[order] = entry->next;
1356
1357 /* We are moving ENTRY to the end of the page table list.
1358 The new page at the head of the list will have NULL in
1359 its PREV field and ENTRY will have NULL in its NEXT field. */
1360 entry->next->prev = NULL;
1361 entry->next = NULL;
1362
1363 /* Append ENTRY to the tail of the list. */
1364 entry->prev = G.page_tails[order];
1365 G.page_tails[order]->next = entry;
1366 G.page_tails[order] = entry;
1367 }
1368
1369 /* Calculate the object's address. */
1370 result = entry->page + object_offset;
1371 if (GATHER_STATISTICS)
1372 ggc_record_overhead (OBJECT_SIZE (order), OBJECT_SIZE (order) - size,
1373 result FINAL_PASS_MEM_STAT);
1374
1375 #ifdef ENABLE_GC_CHECKING
1376 /* Keep poisoning-by-writing-0xaf the object, in an attempt to keep the
1377 exact same semantics in presence of memory bugs, regardless of
1378 ENABLE_VALGRIND_CHECKING. We override this request below. Drop the
1379 handle to avoid handle leak. */
1380 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (result, object_size));
1381
1382 /* `Poison' the entire allocated object, including any padding at
1383 the end. */
1384 memset (result, 0xaf, object_size);
1385
1386 /* Make the bytes after the end of the object unaccessible. Discard the
1387 handle to avoid handle leak. */
1388 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS ((char *) result + size,
1389 object_size - size));
1390 #endif
1391
1392 /* Tell Valgrind that the memory is there, but its content isn't
1393 defined. The bytes at the end of the object are still marked
1394 unaccessible. */
1395 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (result, size));
1396
1397 /* Keep track of how many bytes are being allocated. This
1398 information is used in deciding when to collect. */
1399 G.allocated += object_size;
1400
1401 /* For timevar statistics. */
1402 timevar_ggc_mem_total += object_size;
1403
1404 if (f)
1405 add_finalizer (result, f, s, n);
1406
1407 if (GATHER_STATISTICS)
1408 {
1409 size_t overhead = object_size - size;
1410
1411 G.stats.total_overhead += overhead;
1412 G.stats.total_allocated += object_size;
1413 G.stats.total_overhead_per_order[order] += overhead;
1414 G.stats.total_allocated_per_order[order] += object_size;
1415
1416 if (size <= 32)
1417 {
1418 G.stats.total_overhead_under32 += overhead;
1419 G.stats.total_allocated_under32 += object_size;
1420 }
1421 if (size <= 64)
1422 {
1423 G.stats.total_overhead_under64 += overhead;
1424 G.stats.total_allocated_under64 += object_size;
1425 }
1426 if (size <= 128)
1427 {
1428 G.stats.total_overhead_under128 += overhead;
1429 G.stats.total_allocated_under128 += object_size;
1430 }
1431 }
1432
1433 if (GGC_DEBUG_LEVEL >= 3)
1434 fprintf (G.debug_file,
1435 "Allocating object, requested size=%lu, actual=%lu at %p on %p\n",
1436 (unsigned long) size, (unsigned long) object_size, result,
1437 (void *) entry);
1438
1439 return result;
1440 }
1441
1442 /* Mark function for strings. */
1443
1444 void
gt_ggc_m_S(const void * p)1445 gt_ggc_m_S (const void *p)
1446 {
1447 page_entry *entry;
1448 unsigned bit, word;
1449 unsigned long mask;
1450 unsigned long offset;
1451
1452 if (!p || !ggc_allocated_p (p))
1453 return;
1454
1455 /* Look up the page on which the object is alloced. . */
1456 entry = lookup_page_table_entry (p);
1457 gcc_assert (entry);
1458
1459 /* Calculate the index of the object on the page; this is its bit
1460 position in the in_use_p bitmap. Note that because a char* might
1461 point to the middle of an object, we need special code here to
1462 make sure P points to the start of an object. */
1463 offset = ((const char *) p - entry->page) % object_size_table[entry->order];
1464 if (offset)
1465 {
1466 /* Here we've seen a char* which does not point to the beginning
1467 of an allocated object. We assume it points to the middle of
1468 a STRING_CST. */
1469 gcc_assert (offset == offsetof (struct tree_string, str));
1470 p = ((const char *) p) - offset;
1471 gt_ggc_mx_lang_tree_node (CONST_CAST (void *, p));
1472 return;
1473 }
1474
1475 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1476 word = bit / HOST_BITS_PER_LONG;
1477 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1478
1479 /* If the bit was previously set, skip it. */
1480 if (entry->in_use_p[word] & mask)
1481 return;
1482
1483 /* Otherwise set it, and decrement the free object count. */
1484 entry->in_use_p[word] |= mask;
1485 entry->num_free_objects -= 1;
1486
1487 if (GGC_DEBUG_LEVEL >= 4)
1488 fprintf (G.debug_file, "Marking %p\n", p);
1489
1490 return;
1491 }
1492
1493
1494 /* User-callable entry points for marking string X. */
1495
1496 void
gt_ggc_mx(const char * & x)1497 gt_ggc_mx (const char *& x)
1498 {
1499 gt_ggc_m_S (x);
1500 }
1501
1502 void
gt_ggc_mx(unsigned char * & x)1503 gt_ggc_mx (unsigned char *& x)
1504 {
1505 gt_ggc_m_S (x);
1506 }
1507
1508 void
gt_ggc_mx(unsigned char & x ATTRIBUTE_UNUSED)1509 gt_ggc_mx (unsigned char& x ATTRIBUTE_UNUSED)
1510 {
1511 }
1512
1513 /* If P is not marked, marks it and return false. Otherwise return true.
1514 P must have been allocated by the GC allocator; it mustn't point to
1515 static objects, stack variables, or memory allocated with malloc. */
1516
1517 int
ggc_set_mark(const void * p)1518 ggc_set_mark (const void *p)
1519 {
1520 page_entry *entry;
1521 unsigned bit, word;
1522 unsigned long mask;
1523
1524 /* Look up the page on which the object is alloced. If the object
1525 wasn't allocated by the collector, we'll probably die. */
1526 entry = lookup_page_table_entry (p);
1527 gcc_assert (entry);
1528
1529 /* Calculate the index of the object on the page; this is its bit
1530 position in the in_use_p bitmap. */
1531 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1532 word = bit / HOST_BITS_PER_LONG;
1533 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1534
1535 /* If the bit was previously set, skip it. */
1536 if (entry->in_use_p[word] & mask)
1537 return 1;
1538
1539 /* Otherwise set it, and decrement the free object count. */
1540 entry->in_use_p[word] |= mask;
1541 entry->num_free_objects -= 1;
1542
1543 if (GGC_DEBUG_LEVEL >= 4)
1544 fprintf (G.debug_file, "Marking %p\n", p);
1545
1546 return 0;
1547 }
1548
1549 /* Return 1 if P has been marked, zero otherwise.
1550 P must have been allocated by the GC allocator; it mustn't point to
1551 static objects, stack variables, or memory allocated with malloc. */
1552
1553 int
ggc_marked_p(const void * p)1554 ggc_marked_p (const void *p)
1555 {
1556 page_entry *entry;
1557 unsigned bit, word;
1558 unsigned long mask;
1559
1560 /* Look up the page on which the object is alloced. If the object
1561 wasn't allocated by the collector, we'll probably die. */
1562 entry = lookup_page_table_entry (p);
1563 gcc_assert (entry);
1564
1565 /* Calculate the index of the object on the page; this is its bit
1566 position in the in_use_p bitmap. */
1567 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1568 word = bit / HOST_BITS_PER_LONG;
1569 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1570
1571 return (entry->in_use_p[word] & mask) != 0;
1572 }
1573
1574 /* Return the size of the gc-able object P. */
1575
1576 size_t
ggc_get_size(const void * p)1577 ggc_get_size (const void *p)
1578 {
1579 page_entry *pe = lookup_page_table_entry (p);
1580 return OBJECT_SIZE (pe->order);
1581 }
1582
1583 /* Release the memory for object P. */
1584
1585 void
ggc_free(void * p)1586 ggc_free (void *p)
1587 {
1588 if (in_gc)
1589 return;
1590
1591 page_entry *pe = lookup_page_table_entry (p);
1592 size_t order = pe->order;
1593 size_t size = OBJECT_SIZE (order);
1594
1595 if (GATHER_STATISTICS)
1596 ggc_free_overhead (p);
1597
1598 if (GGC_DEBUG_LEVEL >= 3)
1599 fprintf (G.debug_file,
1600 "Freeing object, actual size=%lu, at %p on %p\n",
1601 (unsigned long) size, p, (void *) pe);
1602
1603 #ifdef ENABLE_GC_CHECKING
1604 /* Poison the data, to indicate the data is garbage. */
1605 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (p, size));
1606 memset (p, 0xa5, size);
1607 #endif
1608 /* Let valgrind know the object is free. */
1609 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS (p, size));
1610
1611 #ifdef ENABLE_GC_ALWAYS_COLLECT
1612 /* In the completely-anal-checking mode, we do *not* immediately free
1613 the data, but instead verify that the data is *actually* not
1614 reachable the next time we collect. */
1615 {
1616 struct free_object *fo = XNEW (struct free_object);
1617 fo->object = p;
1618 fo->next = G.free_object_list;
1619 G.free_object_list = fo;
1620 }
1621 #else
1622 {
1623 unsigned int bit_offset, word, bit;
1624
1625 G.allocated -= size;
1626
1627 /* Mark the object not-in-use. */
1628 bit_offset = OFFSET_TO_BIT (((const char *) p) - pe->page, order);
1629 word = bit_offset / HOST_BITS_PER_LONG;
1630 bit = bit_offset % HOST_BITS_PER_LONG;
1631 pe->in_use_p[word] &= ~(1UL << bit);
1632
1633 if (pe->num_free_objects++ == 0)
1634 {
1635 page_entry *p, *q;
1636
1637 /* If the page is completely full, then it's supposed to
1638 be after all pages that aren't. Since we've freed one
1639 object from a page that was full, we need to move the
1640 page to the head of the list.
1641
1642 PE is the node we want to move. Q is the previous node
1643 and P is the next node in the list. */
1644 q = pe->prev;
1645 if (q && q->num_free_objects == 0)
1646 {
1647 p = pe->next;
1648
1649 q->next = p;
1650
1651 /* If PE was at the end of the list, then Q becomes the
1652 new end of the list. If PE was not the end of the
1653 list, then we need to update the PREV field for P. */
1654 if (!p)
1655 G.page_tails[order] = q;
1656 else
1657 p->prev = q;
1658
1659 /* Move PE to the head of the list. */
1660 pe->next = G.pages[order];
1661 pe->prev = NULL;
1662 G.pages[order]->prev = pe;
1663 G.pages[order] = pe;
1664 }
1665
1666 /* Reset the hint bit to point to the only free object. */
1667 pe->next_bit_hint = bit_offset;
1668 }
1669 }
1670 #endif
1671 }
1672
1673 /* Subroutine of init_ggc which computes the pair of numbers used to
1674 perform division by OBJECT_SIZE (order) and fills in inverse_table[].
1675
1676 This algorithm is taken from Granlund and Montgomery's paper
1677 "Division by Invariant Integers using Multiplication"
1678 (Proc. SIGPLAN PLDI, 1994), section 9 (Exact division by
1679 constants). */
1680
1681 static void
compute_inverse(unsigned order)1682 compute_inverse (unsigned order)
1683 {
1684 size_t size, inv;
1685 unsigned int e;
1686
1687 size = OBJECT_SIZE (order);
1688 e = 0;
1689 while (size % 2 == 0)
1690 {
1691 e++;
1692 size >>= 1;
1693 }
1694
1695 inv = size;
1696 while (inv * size != 1)
1697 inv = inv * (2 - inv*size);
1698
1699 DIV_MULT (order) = inv;
1700 DIV_SHIFT (order) = e;
1701 }
1702
1703 /* Initialize the ggc-mmap allocator. */
1704 void
init_ggc(void)1705 init_ggc (void)
1706 {
1707 static bool init_p = false;
1708 unsigned order;
1709
1710 if (init_p)
1711 return;
1712 init_p = true;
1713
1714 G.pagesize = getpagesize ();
1715 G.lg_pagesize = exact_log2 (G.pagesize);
1716
1717 #ifdef HAVE_MMAP_DEV_ZERO
1718 G.dev_zero_fd = open ("/dev/zero", O_RDONLY);
1719 if (G.dev_zero_fd == -1)
1720 internal_error ("open /dev/zero: %m");
1721 #endif
1722
1723 #if 0
1724 G.debug_file = fopen ("ggc-mmap.debug", "w");
1725 #else
1726 G.debug_file = stdout;
1727 #endif
1728
1729 #ifdef USING_MMAP
1730 /* StunOS has an amazing off-by-one error for the first mmap allocation
1731 after fiddling with RLIMIT_STACK. The result, as hard as it is to
1732 believe, is an unaligned page allocation, which would cause us to
1733 hork badly if we tried to use it. */
1734 {
1735 char *p = alloc_anon (NULL, G.pagesize, true);
1736 struct page_entry *e;
1737 if ((uintptr_t)p & (G.pagesize - 1))
1738 {
1739 /* How losing. Discard this one and try another. If we still
1740 can't get something useful, give up. */
1741
1742 p = alloc_anon (NULL, G.pagesize, true);
1743 gcc_assert (!((uintptr_t)p & (G.pagesize - 1)));
1744 }
1745
1746 /* We have a good page, might as well hold onto it... */
1747 e = XCNEW (struct page_entry);
1748 e->bytes = G.pagesize;
1749 e->page = p;
1750 e->next = G.free_pages;
1751 G.free_pages = e;
1752 }
1753 #endif
1754
1755 /* Initialize the object size table. */
1756 for (order = 0; order < HOST_BITS_PER_PTR; ++order)
1757 object_size_table[order] = (size_t) 1 << order;
1758 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1759 {
1760 size_t s = extra_order_size_table[order - HOST_BITS_PER_PTR];
1761
1762 /* If S is not a multiple of the MAX_ALIGNMENT, then round it up
1763 so that we're sure of getting aligned memory. */
1764 s = ROUND_UP (s, MAX_ALIGNMENT);
1765 object_size_table[order] = s;
1766 }
1767
1768 /* Initialize the objects-per-page and inverse tables. */
1769 for (order = 0; order < NUM_ORDERS; ++order)
1770 {
1771 objects_per_page_table[order] = G.pagesize / OBJECT_SIZE (order);
1772 if (objects_per_page_table[order] == 0)
1773 objects_per_page_table[order] = 1;
1774 compute_inverse (order);
1775 }
1776
1777 /* Reset the size_lookup array to put appropriately sized objects in
1778 the special orders. All objects bigger than the previous power
1779 of two, but no greater than the special size, should go in the
1780 new order. */
1781 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1782 {
1783 int o;
1784 int i;
1785
1786 i = OBJECT_SIZE (order);
1787 if (i >= NUM_SIZE_LOOKUP)
1788 continue;
1789
1790 for (o = size_lookup[i]; o == size_lookup [i]; --i)
1791 size_lookup[i] = order;
1792 }
1793
1794 G.depth_in_use = 0;
1795 G.depth_max = 10;
1796 G.depth = XNEWVEC (unsigned int, G.depth_max);
1797
1798 G.by_depth_in_use = 0;
1799 G.by_depth_max = INITIAL_PTE_COUNT;
1800 G.by_depth = XNEWVEC (page_entry *, G.by_depth_max);
1801 G.save_in_use = XNEWVEC (unsigned long *, G.by_depth_max);
1802
1803 /* Allocate space for the depth 0 finalizers. */
1804 G.finalizers.safe_push (vNULL);
1805 G.vec_finalizers.safe_push (vNULL);
1806 gcc_assert (G.finalizers.length() == 1);
1807 }
1808
1809 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
1810 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
1811
1812 static void
ggc_recalculate_in_use_p(page_entry * p)1813 ggc_recalculate_in_use_p (page_entry *p)
1814 {
1815 unsigned int i;
1816 size_t num_objects;
1817
1818 /* Because the past-the-end bit in in_use_p is always set, we
1819 pretend there is one additional object. */
1820 num_objects = OBJECTS_IN_PAGE (p) + 1;
1821
1822 /* Reset the free object count. */
1823 p->num_free_objects = num_objects;
1824
1825 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
1826 for (i = 0;
1827 i < CEIL (BITMAP_SIZE (num_objects),
1828 sizeof (*p->in_use_p));
1829 ++i)
1830 {
1831 unsigned long j;
1832
1833 /* Something is in use if it is marked, or if it was in use in a
1834 context further down the context stack. */
1835 p->in_use_p[i] |= save_in_use_p (p)[i];
1836
1837 /* Decrement the free object count for every object allocated. */
1838 for (j = p->in_use_p[i]; j; j >>= 1)
1839 p->num_free_objects -= (j & 1);
1840 }
1841
1842 gcc_assert (p->num_free_objects < num_objects);
1843 }
1844
1845 /* Unmark all objects. */
1846
1847 static void
clear_marks(void)1848 clear_marks (void)
1849 {
1850 unsigned order;
1851
1852 for (order = 2; order < NUM_ORDERS; order++)
1853 {
1854 page_entry *p;
1855
1856 for (p = G.pages[order]; p != NULL; p = p->next)
1857 {
1858 size_t num_objects = OBJECTS_IN_PAGE (p);
1859 size_t bitmap_size = BITMAP_SIZE (num_objects + 1);
1860
1861 /* The data should be page-aligned. */
1862 gcc_assert (!((uintptr_t) p->page & (G.pagesize - 1)));
1863
1864 /* Pages that aren't in the topmost context are not collected;
1865 nevertheless, we need their in-use bit vectors to store GC
1866 marks. So, back them up first. */
1867 if (p->context_depth < G.context_depth)
1868 {
1869 if (! save_in_use_p (p))
1870 save_in_use_p (p) = XNEWVAR (unsigned long, bitmap_size);
1871 memcpy (save_in_use_p (p), p->in_use_p, bitmap_size);
1872 }
1873
1874 /* Reset reset the number of free objects and clear the
1875 in-use bits. These will be adjusted by mark_obj. */
1876 p->num_free_objects = num_objects;
1877 memset (p->in_use_p, 0, bitmap_size);
1878
1879 /* Make sure the one-past-the-end bit is always set. */
1880 p->in_use_p[num_objects / HOST_BITS_PER_LONG]
1881 = ((unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG));
1882 }
1883 }
1884 }
1885
1886 /* Check if any blocks with a registered finalizer have become unmarked. If so
1887 run the finalizer and unregister it because the block is about to be freed.
1888 Note that no garantee is made about what order finalizers will run in so
1889 touching other objects in gc memory is extremely unwise. */
1890
1891 static void
ggc_handle_finalizers()1892 ggc_handle_finalizers ()
1893 {
1894 unsigned dlen = G.finalizers.length();
1895 for (unsigned d = G.context_depth; d < dlen; ++d)
1896 {
1897 vec<finalizer> &v = G.finalizers[d];
1898 unsigned length = v.length ();
1899 for (unsigned int i = 0; i < length;)
1900 {
1901 finalizer &f = v[i];
1902 if (!ggc_marked_p (f.addr ()))
1903 {
1904 f.call ();
1905 v.unordered_remove (i);
1906 length--;
1907 }
1908 else
1909 i++;
1910 }
1911 }
1912
1913 gcc_assert (dlen == G.vec_finalizers.length());
1914 for (unsigned d = G.context_depth; d < dlen; ++d)
1915 {
1916 vec<vec_finalizer> &vv = G.vec_finalizers[d];
1917 unsigned length = vv.length ();
1918 for (unsigned int i = 0; i < length;)
1919 {
1920 vec_finalizer &f = vv[i];
1921 if (!ggc_marked_p (f.addr ()))
1922 {
1923 f.call ();
1924 vv.unordered_remove (i);
1925 length--;
1926 }
1927 else
1928 i++;
1929 }
1930 }
1931 }
1932
1933 /* Free all empty pages. Partially empty pages need no attention
1934 because the `mark' bit doubles as an `unused' bit. */
1935
1936 static void
sweep_pages(void)1937 sweep_pages (void)
1938 {
1939 unsigned order;
1940
1941 for (order = 2; order < NUM_ORDERS; order++)
1942 {
1943 /* The last page-entry to consider, regardless of entries
1944 placed at the end of the list. */
1945 page_entry * const last = G.page_tails[order];
1946
1947 size_t num_objects;
1948 size_t live_objects;
1949 page_entry *p, *previous;
1950 int done;
1951
1952 p = G.pages[order];
1953 if (p == NULL)
1954 continue;
1955
1956 previous = NULL;
1957 do
1958 {
1959 page_entry *next = p->next;
1960
1961 /* Loop until all entries have been examined. */
1962 done = (p == last);
1963
1964 num_objects = OBJECTS_IN_PAGE (p);
1965
1966 /* Add all live objects on this page to the count of
1967 allocated memory. */
1968 live_objects = num_objects - p->num_free_objects;
1969
1970 G.allocated += OBJECT_SIZE (order) * live_objects;
1971
1972 /* Only objects on pages in the topmost context should get
1973 collected. */
1974 if (p->context_depth < G.context_depth)
1975 ;
1976
1977 /* Remove the page if it's empty. */
1978 else if (live_objects == 0)
1979 {
1980 /* If P was the first page in the list, then NEXT
1981 becomes the new first page in the list, otherwise
1982 splice P out of the forward pointers. */
1983 if (! previous)
1984 G.pages[order] = next;
1985 else
1986 previous->next = next;
1987
1988 /* Splice P out of the back pointers too. */
1989 if (next)
1990 next->prev = previous;
1991
1992 /* Are we removing the last element? */
1993 if (p == G.page_tails[order])
1994 G.page_tails[order] = previous;
1995 free_page (p);
1996 p = previous;
1997 }
1998
1999 /* If the page is full, move it to the end. */
2000 else if (p->num_free_objects == 0)
2001 {
2002 /* Don't move it if it's already at the end. */
2003 if (p != G.page_tails[order])
2004 {
2005 /* Move p to the end of the list. */
2006 p->next = NULL;
2007 p->prev = G.page_tails[order];
2008 G.page_tails[order]->next = p;
2009
2010 /* Update the tail pointer... */
2011 G.page_tails[order] = p;
2012
2013 /* ... and the head pointer, if necessary. */
2014 if (! previous)
2015 G.pages[order] = next;
2016 else
2017 previous->next = next;
2018
2019 /* And update the backpointer in NEXT if necessary. */
2020 if (next)
2021 next->prev = previous;
2022
2023 p = previous;
2024 }
2025 }
2026
2027 /* If we've fallen through to here, it's a page in the
2028 topmost context that is neither full nor empty. Such a
2029 page must precede pages at lesser context depth in the
2030 list, so move it to the head. */
2031 else if (p != G.pages[order])
2032 {
2033 previous->next = p->next;
2034
2035 /* Update the backchain in the next node if it exists. */
2036 if (p->next)
2037 p->next->prev = previous;
2038
2039 /* Move P to the head of the list. */
2040 p->next = G.pages[order];
2041 p->prev = NULL;
2042 G.pages[order]->prev = p;
2043
2044 /* Update the head pointer. */
2045 G.pages[order] = p;
2046
2047 /* Are we moving the last element? */
2048 if (G.page_tails[order] == p)
2049 G.page_tails[order] = previous;
2050 p = previous;
2051 }
2052
2053 previous = p;
2054 p = next;
2055 }
2056 while (! done);
2057
2058 /* Now, restore the in_use_p vectors for any pages from contexts
2059 other than the current one. */
2060 for (p = G.pages[order]; p; p = p->next)
2061 if (p->context_depth != G.context_depth)
2062 ggc_recalculate_in_use_p (p);
2063 }
2064 }
2065
2066 #ifdef ENABLE_GC_CHECKING
2067 /* Clobber all free objects. */
2068
2069 static void
poison_pages(void)2070 poison_pages (void)
2071 {
2072 unsigned order;
2073
2074 for (order = 2; order < NUM_ORDERS; order++)
2075 {
2076 size_t size = OBJECT_SIZE (order);
2077 page_entry *p;
2078
2079 for (p = G.pages[order]; p != NULL; p = p->next)
2080 {
2081 size_t num_objects;
2082 size_t i;
2083
2084 if (p->context_depth != G.context_depth)
2085 /* Since we don't do any collection for pages in pushed
2086 contexts, there's no need to do any poisoning. And
2087 besides, the IN_USE_P array isn't valid until we pop
2088 contexts. */
2089 continue;
2090
2091 num_objects = OBJECTS_IN_PAGE (p);
2092 for (i = 0; i < num_objects; i++)
2093 {
2094 size_t word, bit;
2095 word = i / HOST_BITS_PER_LONG;
2096 bit = i % HOST_BITS_PER_LONG;
2097 if (((p->in_use_p[word] >> bit) & 1) == 0)
2098 {
2099 char *object = p->page + i * size;
2100
2101 /* Keep poison-by-write when we expect to use Valgrind,
2102 so the exact same memory semantics is kept, in case
2103 there are memory errors. We override this request
2104 below. */
2105 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (object,
2106 size));
2107 memset (object, 0xa5, size);
2108
2109 /* Drop the handle to avoid handle leak. */
2110 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS (object, size));
2111 }
2112 }
2113 }
2114 }
2115 }
2116 #else
2117 #define poison_pages()
2118 #endif
2119
2120 #ifdef ENABLE_GC_ALWAYS_COLLECT
2121 /* Validate that the reportedly free objects actually are. */
2122
2123 static void
validate_free_objects(void)2124 validate_free_objects (void)
2125 {
2126 struct free_object *f, *next, *still_free = NULL;
2127
2128 for (f = G.free_object_list; f ; f = next)
2129 {
2130 page_entry *pe = lookup_page_table_entry (f->object);
2131 size_t bit, word;
2132
2133 bit = OFFSET_TO_BIT ((char *)f->object - pe->page, pe->order);
2134 word = bit / HOST_BITS_PER_LONG;
2135 bit = bit % HOST_BITS_PER_LONG;
2136 next = f->next;
2137
2138 /* Make certain it isn't visible from any root. Notice that we
2139 do this check before sweep_pages merges save_in_use_p. */
2140 gcc_assert (!(pe->in_use_p[word] & (1UL << bit)));
2141
2142 /* If the object comes from an outer context, then retain the
2143 free_object entry, so that we can verify that the address
2144 isn't live on the stack in some outer context. */
2145 if (pe->context_depth != G.context_depth)
2146 {
2147 f->next = still_free;
2148 still_free = f;
2149 }
2150 else
2151 free (f);
2152 }
2153
2154 G.free_object_list = still_free;
2155 }
2156 #else
2157 #define validate_free_objects()
2158 #endif
2159
2160 /* Top level mark-and-sweep routine. */
2161
2162 void
ggc_collect(void)2163 ggc_collect (void)
2164 {
2165 /* Avoid frequent unnecessary work by skipping collection if the
2166 total allocations haven't expanded much since the last
2167 collection. */
2168 float allocated_last_gc =
2169 MAX (G.allocated_last_gc, (size_t)PARAM_VALUE (GGC_MIN_HEAPSIZE) * 1024);
2170
2171 float min_expand = allocated_last_gc * PARAM_VALUE (GGC_MIN_EXPAND) / 100;
2172 if (G.allocated < allocated_last_gc + min_expand && !ggc_force_collect)
2173 return;
2174
2175 timevar_push (TV_GC);
2176 if (!quiet_flag)
2177 fprintf (stderr, " {GC %luk -> ", (unsigned long) G.allocated / 1024);
2178 if (GGC_DEBUG_LEVEL >= 2)
2179 fprintf (G.debug_file, "BEGIN COLLECTING\n");
2180
2181 /* Zero the total allocated bytes. This will be recalculated in the
2182 sweep phase. */
2183 G.allocated = 0;
2184
2185 /* Release the pages we freed the last time we collected, but didn't
2186 reuse in the interim. */
2187 release_pages ();
2188
2189 /* Indicate that we've seen collections at this context depth. */
2190 G.context_depth_collections = ((unsigned long)1 << (G.context_depth + 1)) - 1;
2191
2192 invoke_plugin_callbacks (PLUGIN_GGC_START, NULL);
2193
2194 in_gc = true;
2195 clear_marks ();
2196 ggc_mark_roots ();
2197 ggc_handle_finalizers ();
2198
2199 if (GATHER_STATISTICS)
2200 ggc_prune_overhead_list ();
2201
2202 poison_pages ();
2203 validate_free_objects ();
2204 sweep_pages ();
2205
2206 in_gc = false;
2207 G.allocated_last_gc = G.allocated;
2208
2209 invoke_plugin_callbacks (PLUGIN_GGC_END, NULL);
2210
2211 timevar_pop (TV_GC);
2212
2213 if (!quiet_flag)
2214 fprintf (stderr, "%luk}", (unsigned long) G.allocated / 1024);
2215 if (GGC_DEBUG_LEVEL >= 2)
2216 fprintf (G.debug_file, "END COLLECTING\n");
2217 }
2218
2219 /* Assume that all GGC memory is reachable and grow the limits for next collection.
2220 With checking, trigger GGC so -Q compilation outputs how much of memory really is
2221 reachable. */
2222
2223 void
ggc_grow(void)2224 ggc_grow (void)
2225 {
2226 if (!flag_checking)
2227 G.allocated_last_gc = MAX (G.allocated_last_gc,
2228 G.allocated);
2229 else
2230 ggc_collect ();
2231 if (!quiet_flag)
2232 fprintf (stderr, " {GC start %luk} ", (unsigned long) G.allocated / 1024);
2233 }
2234
2235 /* Print allocation statistics. */
2236 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \
2237 ? (x) \
2238 : ((x) < 1024*1024*10 \
2239 ? (x) / 1024 \
2240 : (x) / (1024*1024))))
2241 #define STAT_LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
2242
2243 void
ggc_print_statistics(void)2244 ggc_print_statistics (void)
2245 {
2246 struct ggc_statistics stats;
2247 unsigned int i;
2248 size_t total_overhead = 0;
2249
2250 /* Clear the statistics. */
2251 memset (&stats, 0, sizeof (stats));
2252
2253 /* Make sure collection will really occur. */
2254 G.allocated_last_gc = 0;
2255
2256 /* Collect and print the statistics common across collectors. */
2257 ggc_print_common_statistics (stderr, &stats);
2258
2259 /* Release free pages so that we will not count the bytes allocated
2260 there as part of the total allocated memory. */
2261 release_pages ();
2262
2263 /* Collect some information about the various sizes of
2264 allocation. */
2265 fprintf (stderr,
2266 "Memory still allocated at the end of the compilation process\n");
2267 fprintf (stderr, "%-8s %10s %10s %10s\n",
2268 "Size", "Allocated", "Used", "Overhead");
2269 for (i = 0; i < NUM_ORDERS; ++i)
2270 {
2271 page_entry *p;
2272 size_t allocated;
2273 size_t in_use;
2274 size_t overhead;
2275
2276 /* Skip empty entries. */
2277 if (!G.pages[i])
2278 continue;
2279
2280 overhead = allocated = in_use = 0;
2281
2282 /* Figure out the total number of bytes allocated for objects of
2283 this size, and how many of them are actually in use. Also figure
2284 out how much memory the page table is using. */
2285 for (p = G.pages[i]; p; p = p->next)
2286 {
2287 allocated += p->bytes;
2288 in_use +=
2289 (OBJECTS_IN_PAGE (p) - p->num_free_objects) * OBJECT_SIZE (i);
2290
2291 overhead += (sizeof (page_entry) - sizeof (long)
2292 + BITMAP_SIZE (OBJECTS_IN_PAGE (p) + 1));
2293 }
2294 fprintf (stderr, "%-8lu %10lu%c %10lu%c %10lu%c\n",
2295 (unsigned long) OBJECT_SIZE (i),
2296 SCALE (allocated), STAT_LABEL (allocated),
2297 SCALE (in_use), STAT_LABEL (in_use),
2298 SCALE (overhead), STAT_LABEL (overhead));
2299 total_overhead += overhead;
2300 }
2301 fprintf (stderr, "%-8s %10lu%c %10lu%c %10lu%c\n", "Total",
2302 SCALE (G.bytes_mapped), STAT_LABEL (G.bytes_mapped),
2303 SCALE (G.allocated), STAT_LABEL (G.allocated),
2304 SCALE (total_overhead), STAT_LABEL (total_overhead));
2305
2306 if (GATHER_STATISTICS)
2307 {
2308 fprintf (stderr, "\nTotal allocations and overheads during "
2309 "the compilation process\n");
2310
2311 fprintf (stderr, "Total Overhead: %10"
2312 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_overhead);
2313 fprintf (stderr, "Total Allocated: %10"
2314 HOST_LONG_LONG_FORMAT "d\n",
2315 G.stats.total_allocated);
2316
2317 fprintf (stderr, "Total Overhead under 32B: %10"
2318 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_overhead_under32);
2319 fprintf (stderr, "Total Allocated under 32B: %10"
2320 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_allocated_under32);
2321 fprintf (stderr, "Total Overhead under 64B: %10"
2322 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_overhead_under64);
2323 fprintf (stderr, "Total Allocated under 64B: %10"
2324 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_allocated_under64);
2325 fprintf (stderr, "Total Overhead under 128B: %10"
2326 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_overhead_under128);
2327 fprintf (stderr, "Total Allocated under 128B: %10"
2328 HOST_LONG_LONG_FORMAT "d\n", G.stats.total_allocated_under128);
2329
2330 for (i = 0; i < NUM_ORDERS; i++)
2331 if (G.stats.total_allocated_per_order[i])
2332 {
2333 fprintf (stderr, "Total Overhead page size %9lu: %10"
2334 HOST_LONG_LONG_FORMAT "d\n",
2335 (unsigned long) OBJECT_SIZE (i),
2336 G.stats.total_overhead_per_order[i]);
2337 fprintf (stderr, "Total Allocated page size %9lu: %10"
2338 HOST_LONG_LONG_FORMAT "d\n",
2339 (unsigned long) OBJECT_SIZE (i),
2340 G.stats.total_allocated_per_order[i]);
2341 }
2342 }
2343 }
2344
2345 struct ggc_pch_ondisk
2346 {
2347 unsigned totals[NUM_ORDERS];
2348 };
2349
2350 struct ggc_pch_data
2351 {
2352 struct ggc_pch_ondisk d;
2353 uintptr_t base[NUM_ORDERS];
2354 size_t written[NUM_ORDERS];
2355 };
2356
2357 struct ggc_pch_data *
init_ggc_pch(void)2358 init_ggc_pch (void)
2359 {
2360 return XCNEW (struct ggc_pch_data);
2361 }
2362
2363 void
ggc_pch_count_object(struct ggc_pch_data * d,void * x ATTRIBUTE_UNUSED,size_t size,bool is_string ATTRIBUTE_UNUSED)2364 ggc_pch_count_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2365 size_t size, bool is_string ATTRIBUTE_UNUSED)
2366 {
2367 unsigned order;
2368
2369 if (size < NUM_SIZE_LOOKUP)
2370 order = size_lookup[size];
2371 else
2372 {
2373 order = 10;
2374 while (size > OBJECT_SIZE (order))
2375 order++;
2376 }
2377
2378 d->d.totals[order]++;
2379 }
2380
2381 size_t
ggc_pch_total_size(struct ggc_pch_data * d)2382 ggc_pch_total_size (struct ggc_pch_data *d)
2383 {
2384 size_t a = 0;
2385 unsigned i;
2386
2387 for (i = 0; i < NUM_ORDERS; i++)
2388 a += PAGE_ALIGN (d->d.totals[i] * OBJECT_SIZE (i));
2389 return a;
2390 }
2391
2392 void
ggc_pch_this_base(struct ggc_pch_data * d,void * base)2393 ggc_pch_this_base (struct ggc_pch_data *d, void *base)
2394 {
2395 uintptr_t a = (uintptr_t) base;
2396 unsigned i;
2397
2398 for (i = 0; i < NUM_ORDERS; i++)
2399 {
2400 d->base[i] = a;
2401 a += PAGE_ALIGN (d->d.totals[i] * OBJECT_SIZE (i));
2402 }
2403 }
2404
2405
2406 char *
ggc_pch_alloc_object(struct ggc_pch_data * d,void * x ATTRIBUTE_UNUSED,size_t size,bool is_string ATTRIBUTE_UNUSED)2407 ggc_pch_alloc_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2408 size_t size, bool is_string ATTRIBUTE_UNUSED)
2409 {
2410 unsigned order;
2411 char *result;
2412
2413 if (size < NUM_SIZE_LOOKUP)
2414 order = size_lookup[size];
2415 else
2416 {
2417 order = 10;
2418 while (size > OBJECT_SIZE (order))
2419 order++;
2420 }
2421
2422 result = (char *) d->base[order];
2423 d->base[order] += OBJECT_SIZE (order);
2424 return result;
2425 }
2426
2427 void
ggc_pch_prepare_write(struct ggc_pch_data * d ATTRIBUTE_UNUSED,FILE * f ATTRIBUTE_UNUSED)2428 ggc_pch_prepare_write (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
2429 FILE *f ATTRIBUTE_UNUSED)
2430 {
2431 /* Nothing to do. */
2432 }
2433
2434 void
ggc_pch_write_object(struct ggc_pch_data * d,FILE * f,void * x,void * newx ATTRIBUTE_UNUSED,size_t size,bool is_string ATTRIBUTE_UNUSED)2435 ggc_pch_write_object (struct ggc_pch_data *d,
2436 FILE *f, void *x, void *newx ATTRIBUTE_UNUSED,
2437 size_t size, bool is_string ATTRIBUTE_UNUSED)
2438 {
2439 unsigned order;
2440 static const char emptyBytes[256] = { 0 };
2441
2442 if (size < NUM_SIZE_LOOKUP)
2443 order = size_lookup[size];
2444 else
2445 {
2446 order = 10;
2447 while (size > OBJECT_SIZE (order))
2448 order++;
2449 }
2450
2451 if (fwrite (x, size, 1, f) != 1)
2452 fatal_error (input_location, "can%'t write PCH file: %m");
2453
2454 /* If SIZE is not the same as OBJECT_SIZE(order), then we need to pad the
2455 object out to OBJECT_SIZE(order). This happens for strings. */
2456
2457 if (size != OBJECT_SIZE (order))
2458 {
2459 unsigned padding = OBJECT_SIZE (order) - size;
2460
2461 /* To speed small writes, we use a nulled-out array that's larger
2462 than most padding requests as the source for our null bytes. This
2463 permits us to do the padding with fwrite() rather than fseek(), and
2464 limits the chance the OS may try to flush any outstanding writes. */
2465 if (padding <= sizeof (emptyBytes))
2466 {
2467 if (fwrite (emptyBytes, 1, padding, f) != padding)
2468 fatal_error (input_location, "can%'t write PCH file");
2469 }
2470 else
2471 {
2472 /* Larger than our buffer? Just default to fseek. */
2473 if (fseek (f, padding, SEEK_CUR) != 0)
2474 fatal_error (input_location, "can%'t write PCH file");
2475 }
2476 }
2477
2478 d->written[order]++;
2479 if (d->written[order] == d->d.totals[order]
2480 && fseek (f, ROUND_UP_VALUE (d->d.totals[order] * OBJECT_SIZE (order),
2481 G.pagesize),
2482 SEEK_CUR) != 0)
2483 fatal_error (input_location, "can%'t write PCH file: %m");
2484 }
2485
2486 void
ggc_pch_finish(struct ggc_pch_data * d,FILE * f)2487 ggc_pch_finish (struct ggc_pch_data *d, FILE *f)
2488 {
2489 if (fwrite (&d->d, sizeof (d->d), 1, f) != 1)
2490 fatal_error (input_location, "can%'t write PCH file: %m");
2491 free (d);
2492 }
2493
2494 /* Move the PCH PTE entries just added to the end of by_depth, to the
2495 front. */
2496
2497 static void
move_ptes_to_front(int count_old_page_tables,int count_new_page_tables)2498 move_ptes_to_front (int count_old_page_tables, int count_new_page_tables)
2499 {
2500 unsigned i;
2501
2502 /* First, we swap the new entries to the front of the varrays. */
2503 page_entry **new_by_depth;
2504 unsigned long **new_save_in_use;
2505
2506 new_by_depth = XNEWVEC (page_entry *, G.by_depth_max);
2507 new_save_in_use = XNEWVEC (unsigned long *, G.by_depth_max);
2508
2509 memcpy (&new_by_depth[0],
2510 &G.by_depth[count_old_page_tables],
2511 count_new_page_tables * sizeof (void *));
2512 memcpy (&new_by_depth[count_new_page_tables],
2513 &G.by_depth[0],
2514 count_old_page_tables * sizeof (void *));
2515 memcpy (&new_save_in_use[0],
2516 &G.save_in_use[count_old_page_tables],
2517 count_new_page_tables * sizeof (void *));
2518 memcpy (&new_save_in_use[count_new_page_tables],
2519 &G.save_in_use[0],
2520 count_old_page_tables * sizeof (void *));
2521
2522 free (G.by_depth);
2523 free (G.save_in_use);
2524
2525 G.by_depth = new_by_depth;
2526 G.save_in_use = new_save_in_use;
2527
2528 /* Now update all the index_by_depth fields. */
2529 for (i = G.by_depth_in_use; i > 0; --i)
2530 {
2531 page_entry *p = G.by_depth[i-1];
2532 p->index_by_depth = i-1;
2533 }
2534
2535 /* And last, we update the depth pointers in G.depth. The first
2536 entry is already 0, and context 0 entries always start at index
2537 0, so there is nothing to update in the first slot. We need a
2538 second slot, only if we have old ptes, and if we do, they start
2539 at index count_new_page_tables. */
2540 if (count_old_page_tables)
2541 push_depth (count_new_page_tables);
2542 }
2543
2544 void
ggc_pch_read(FILE * f,void * addr)2545 ggc_pch_read (FILE *f, void *addr)
2546 {
2547 struct ggc_pch_ondisk d;
2548 unsigned i;
2549 char *offs = (char *) addr;
2550 unsigned long count_old_page_tables;
2551 unsigned long count_new_page_tables;
2552
2553 count_old_page_tables = G.by_depth_in_use;
2554
2555 /* We've just read in a PCH file. So, every object that used to be
2556 allocated is now free. */
2557 clear_marks ();
2558 #ifdef ENABLE_GC_CHECKING
2559 poison_pages ();
2560 #endif
2561 /* Since we free all the allocated objects, the free list becomes
2562 useless. Validate it now, which will also clear it. */
2563 validate_free_objects ();
2564
2565 /* No object read from a PCH file should ever be freed. So, set the
2566 context depth to 1, and set the depth of all the currently-allocated
2567 pages to be 1 too. PCH pages will have depth 0. */
2568 gcc_assert (!G.context_depth);
2569 G.context_depth = 1;
2570 /* Allocate space for the depth 1 finalizers. */
2571 G.finalizers.safe_push (vNULL);
2572 G.vec_finalizers.safe_push (vNULL);
2573 gcc_assert (G.finalizers.length() == 2);
2574 for (i = 0; i < NUM_ORDERS; i++)
2575 {
2576 page_entry *p;
2577 for (p = G.pages[i]; p != NULL; p = p->next)
2578 p->context_depth = G.context_depth;
2579 }
2580
2581 /* Allocate the appropriate page-table entries for the pages read from
2582 the PCH file. */
2583 if (fread (&d, sizeof (d), 1, f) != 1)
2584 fatal_error (input_location, "can%'t read PCH file: %m");
2585
2586 for (i = 0; i < NUM_ORDERS; i++)
2587 {
2588 struct page_entry *entry;
2589 char *pte;
2590 size_t bytes;
2591 size_t num_objs;
2592 size_t j;
2593
2594 if (d.totals[i] == 0)
2595 continue;
2596
2597 bytes = PAGE_ALIGN (d.totals[i] * OBJECT_SIZE (i));
2598 num_objs = bytes / OBJECT_SIZE (i);
2599 entry = XCNEWVAR (struct page_entry, (sizeof (struct page_entry)
2600 - sizeof (long)
2601 + BITMAP_SIZE (num_objs + 1)));
2602 entry->bytes = bytes;
2603 entry->page = offs;
2604 entry->context_depth = 0;
2605 offs += bytes;
2606 entry->num_free_objects = 0;
2607 entry->order = i;
2608
2609 for (j = 0;
2610 j + HOST_BITS_PER_LONG <= num_objs + 1;
2611 j += HOST_BITS_PER_LONG)
2612 entry->in_use_p[j / HOST_BITS_PER_LONG] = -1;
2613 for (; j < num_objs + 1; j++)
2614 entry->in_use_p[j / HOST_BITS_PER_LONG]
2615 |= 1L << (j % HOST_BITS_PER_LONG);
2616
2617 for (pte = entry->page;
2618 pte < entry->page + entry->bytes;
2619 pte += G.pagesize)
2620 set_page_table_entry (pte, entry);
2621
2622 if (G.page_tails[i] != NULL)
2623 G.page_tails[i]->next = entry;
2624 else
2625 G.pages[i] = entry;
2626 G.page_tails[i] = entry;
2627
2628 /* We start off by just adding all the new information to the
2629 end of the varrays, later, we will move the new information
2630 to the front of the varrays, as the PCH page tables are at
2631 context 0. */
2632 push_by_depth (entry, 0);
2633 }
2634
2635 /* Now, we update the various data structures that speed page table
2636 handling. */
2637 count_new_page_tables = G.by_depth_in_use - count_old_page_tables;
2638
2639 move_ptes_to_front (count_old_page_tables, count_new_page_tables);
2640
2641 /* Update the statistics. */
2642 G.allocated = G.allocated_last_gc = offs - (char *)addr;
2643 }
2644