1 /* "Bag-of-pages" garbage collector for the GNU compiler.
2 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
24 #include "coretypes.h"
34 #include "tree-flow.h"
35 #ifdef ENABLE_VALGRIND_CHECKING
36 # ifdef HAVE_VALGRIND_MEMCHECK_H
37 # include <valgrind/memcheck.h>
38 # elif defined HAVE_MEMCHECK_H
39 # include <memcheck.h>
41 # include <valgrind.h>
44 /* Avoid #ifdef:s when we can help it. */
45 #define VALGRIND_DISCARD(x)
48 /* Prefer MAP_ANON(YMOUS) to /dev/zero, since we don't need to keep a
49 file open. Prefer either to valloc. */
51 # undef HAVE_MMAP_DEV_ZERO
53 # include <sys/mman.h>
55 # define MAP_FAILED -1
57 # if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
58 # define MAP_ANONYMOUS MAP_ANON
64 #ifdef HAVE_MMAP_DEV_ZERO
66 # include <sys/mman.h>
68 # define MAP_FAILED -1
75 #define USING_MALLOC_PAGE_GROUPS
80 This garbage-collecting allocator allocates objects on one of a set
81 of pages. Each page can allocate objects of a single size only;
82 available sizes are powers of two starting at four bytes. The size
83 of an allocation request is rounded up to the next power of two
84 (`order'), and satisfied from the appropriate page.
86 Each page is recorded in a page-entry, which also maintains an
87 in-use bitmap of object positions on the page. This allows the
88 allocation state of a particular object to be flipped without
89 touching the page itself.
91 Each page-entry also has a context depth, which is used to track
92 pushing and popping of allocation contexts. Only objects allocated
93 in the current (highest-numbered) context may be collected.
95 Page entries are arranged in an array of singly-linked lists. The
96 array is indexed by the allocation size, in bits, of the pages on
97 it; i.e. all pages on a list allocate objects of the same size.
98 Pages are ordered on the list such that all non-full pages precede
99 all full pages, with non-full pages arranged in order of decreasing
102 Empty pages (of all orders) are kept on a single page cache list,
103 and are considered first when new pages are required; they are
104 deallocated at the start of the next collection if they haven't
105 been recycled by then. */
107 /* Define GGC_DEBUG_LEVEL to print debugging information.
108 0: No debugging output.
109 1: GC statistics only.
110 2: Page-entry allocations/deallocations as well.
111 3: Object allocations as well.
112 4: Object marks as well. */
113 #define GGC_DEBUG_LEVEL (0)
115 #ifndef HOST_BITS_PER_PTR
116 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
120 /* A two-level tree is used to look up the page-entry for a given
121 pointer. Two chunks of the pointer's bits are extracted to index
122 the first and second levels of the tree, as follows:
126 msb +----------------+----+------+------+ lsb
132 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
133 pages are aligned on system page boundaries. The next most
134 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
135 index values in the lookup table, respectively.
137 For 32-bit architectures and the settings below, there are no
138 leftover bits. For architectures with wider pointers, the lookup
139 tree points to a list of pages, which must be scanned to find the
142 #define PAGE_L1_BITS (8)
143 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
144 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
145 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
147 #define LOOKUP_L1(p) \
148 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
150 #define LOOKUP_L2(p) \
151 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
153 /* The number of objects per allocation page, for objects on a page of
154 the indicated ORDER. */
155 #define OBJECTS_PER_PAGE(ORDER) objects_per_page_table[ORDER]
157 /* The number of objects in P. */
158 #define OBJECTS_IN_PAGE(P) ((P)->bytes / OBJECT_SIZE ((P)->order))
160 /* The size of an object on a page of the indicated ORDER. */
161 #define OBJECT_SIZE(ORDER) object_size_table[ORDER]
163 /* For speed, we avoid doing a general integer divide to locate the
164 offset in the allocation bitmap, by precalculating numbers M, S
165 such that (O * M) >> S == O / Z (modulo 2^32), for any offset O
166 within the page which is evenly divisible by the object size Z. */
167 #define DIV_MULT(ORDER) inverse_table[ORDER].mult
168 #define DIV_SHIFT(ORDER) inverse_table[ORDER].shift
169 #define OFFSET_TO_BIT(OFFSET, ORDER) \
170 (((OFFSET) * DIV_MULT (ORDER)) >> DIV_SHIFT (ORDER))
172 /* The number of extra orders, not corresponding to power-of-two sized
175 #define NUM_EXTRA_ORDERS ARRAY_SIZE (extra_order_size_table)
177 #define RTL_SIZE(NSLOTS) \
178 (RTX_HDR_SIZE + (NSLOTS) * sizeof (rtunion))
180 #define TREE_EXP_SIZE(OPS) \
181 (sizeof (struct tree_exp) + ((OPS) - 1) * sizeof (tree))
183 /* The Ith entry is the maximum size of an object to be stored in the
184 Ith extra order. Adding a new entry to this array is the *only*
185 thing you need to do to add a new special allocation size. */
187 static const size_t extra_order_size_table[] = {
188 sizeof (struct stmt_ann_d),
189 sizeof (struct tree_decl_non_common),
190 sizeof (struct tree_field_decl),
191 sizeof (struct tree_parm_decl),
192 sizeof (struct tree_var_decl),
193 sizeof (struct tree_list),
194 sizeof (struct function),
195 sizeof (struct basic_block_def),
197 RTL_SIZE (2), /* MEM, PLUS, etc. */
198 RTL_SIZE (9), /* INSN */
201 /* The total number of orders. */
203 #define NUM_ORDERS (HOST_BITS_PER_PTR + NUM_EXTRA_ORDERS)
205 /* We use this structure to determine the alignment required for
206 allocations. For power-of-two sized allocations, that's not a
207 problem, but it does matter for odd-sized allocations. */
209 struct max_alignment {
217 /* The biggest alignment required. */
219 #define MAX_ALIGNMENT (offsetof (struct max_alignment, u))
221 /* Compute the smallest nonnegative number which when added to X gives
224 #define ROUND_UP_VALUE(x, f) ((f) - 1 - ((f) - 1 + (x)) % (f))
226 /* Compute the smallest multiple of F that is >= X. */
228 #define ROUND_UP(x, f) (CEIL (x, f) * (f))
230 /* The Ith entry is the number of objects on a page or order I. */
232 static unsigned objects_per_page_table[NUM_ORDERS];
234 /* The Ith entry is the size of an object on a page of order I. */
236 static size_t object_size_table[NUM_ORDERS];
238 /* The Ith entry is a pair of numbers (mult, shift) such that
239 ((k * mult) >> shift) mod 2^32 == (k / OBJECT_SIZE(I)) mod 2^32,
240 for all k evenly divisible by OBJECT_SIZE(I). */
247 inverse_table[NUM_ORDERS];
249 /* A page_entry records the status of an allocation page. This
250 structure is dynamically sized to fit the bitmap in_use_p. */
251 typedef struct page_entry
253 /* The next page-entry with objects of the same size, or NULL if
254 this is the last page-entry. */
255 struct page_entry *next;
257 /* The previous page-entry with objects of the same size, or NULL if
258 this is the first page-entry. The PREV pointer exists solely to
259 keep the cost of ggc_free manageable. */
260 struct page_entry *prev;
262 /* The number of bytes allocated. (This will always be a multiple
263 of the host system page size.) */
266 /* The address at which the memory is allocated. */
269 #ifdef USING_MALLOC_PAGE_GROUPS
270 /* Back pointer to the page group this page came from. */
271 struct page_group *group;
274 /* This is the index in the by_depth varray where this page table
276 unsigned long index_by_depth;
278 /* Context depth of this page. */
279 unsigned short context_depth;
281 /* The number of free objects remaining on this page. */
282 unsigned short num_free_objects;
284 /* A likely candidate for the bit position of a free object for the
285 next allocation from this page. */
286 unsigned short next_bit_hint;
288 /* The lg of size of objects allocated from this page. */
291 /* A bit vector indicating whether or not objects are in use. The
292 Nth bit is one if the Nth object on this page is allocated. This
293 array is dynamically sized. */
294 unsigned long in_use_p[1];
297 #ifdef USING_MALLOC_PAGE_GROUPS
298 /* A page_group describes a large allocation from malloc, from which
299 we parcel out aligned pages. */
300 typedef struct page_group
302 /* A linked list of all extant page groups. */
303 struct page_group *next;
305 /* The address we received from malloc. */
308 /* The size of the block. */
311 /* A bitmask of pages in use. */
316 #if HOST_BITS_PER_PTR <= 32
318 /* On 32-bit hosts, we use a two level page table, as pictured above. */
319 typedef page_entry **page_table[PAGE_L1_SIZE];
323 /* On 64-bit hosts, we use the same two level page tables plus a linked
324 list that disambiguates the top 32-bits. There will almost always be
325 exactly one entry in the list. */
326 typedef struct page_table_chain
328 struct page_table_chain *next;
330 page_entry **table[PAGE_L1_SIZE];
335 /* The rest of the global variables. */
336 static struct globals
338 /* The Nth element in this array is a page with objects of size 2^N.
339 If there are any pages with free objects, they will be at the
340 head of the list. NULL if there are no page-entries for this
342 page_entry *pages[NUM_ORDERS];
344 /* The Nth element in this array is the last page with objects of
345 size 2^N. NULL if there are no page-entries for this object
347 page_entry *page_tails[NUM_ORDERS];
349 /* Lookup table for associating allocation pages with object addresses. */
352 /* The system's page size. */
356 /* Bytes currently allocated. */
359 /* Bytes currently allocated at the end of the last collection. */
360 size_t allocated_last_gc;
362 /* Total amount of memory mapped. */
365 /* Bit N set if any allocations have been done at context depth N. */
366 unsigned long context_depth_allocations;
368 /* Bit N set if any collections have been done at context depth N. */
369 unsigned long context_depth_collections;
371 /* The current depth in the context stack. */
372 unsigned short context_depth;
374 /* A file descriptor open to /dev/zero for reading. */
375 #if defined (HAVE_MMAP_DEV_ZERO)
379 /* A cache of free system pages. */
380 page_entry *free_pages;
382 #ifdef USING_MALLOC_PAGE_GROUPS
383 page_group *page_groups;
386 /* The file descriptor for debugging output. */
389 /* Current number of elements in use in depth below. */
390 unsigned int depth_in_use;
392 /* Maximum number of elements that can be used before resizing. */
393 unsigned int depth_max;
395 /* Each element of this arry is an index in by_depth where the given
396 depth starts. This structure is indexed by that given depth we
397 are interested in. */
400 /* Current number of elements in use in by_depth below. */
401 unsigned int by_depth_in_use;
403 /* Maximum number of elements that can be used before resizing. */
404 unsigned int by_depth_max;
406 /* Each element of this array is a pointer to a page_entry, all
407 page_entries can be found in here by increasing depth.
408 index_by_depth in the page_entry is the index into this data
409 structure where that page_entry can be found. This is used to
410 speed up finding all page_entries at a particular depth. */
411 page_entry **by_depth;
413 /* Each element is a pointer to the saved in_use_p bits, if any,
414 zero otherwise. We allocate them all together, to enable a
415 better runtime data access pattern. */
416 unsigned long **save_in_use;
418 #ifdef ENABLE_GC_ALWAYS_COLLECT
419 /* List of free objects to be verified as actually free on the
424 struct free_object *next;
428 #ifdef GATHER_STATISTICS
431 /* Total memory allocated with ggc_alloc. */
432 unsigned long long total_allocated;
433 /* Total overhead for memory to be allocated with ggc_alloc. */
434 unsigned long long total_overhead;
436 /* Total allocations and overhead for sizes less than 32, 64 and 128.
437 These sizes are interesting because they are typical cache line
440 unsigned long long total_allocated_under32;
441 unsigned long long total_overhead_under32;
443 unsigned long long total_allocated_under64;
444 unsigned long long total_overhead_under64;
446 unsigned long long total_allocated_under128;
447 unsigned long long total_overhead_under128;
449 /* The allocations for each of the allocation orders. */
450 unsigned long long total_allocated_per_order[NUM_ORDERS];
452 /* The overhead for each of the allocation orders. */
453 unsigned long long total_overhead_per_order[NUM_ORDERS];
458 /* The size in bytes required to maintain a bitmap for the objects
460 #define BITMAP_SIZE(Num_objects) \
461 (CEIL ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
463 /* Allocate pages in chunks of this size, to throttle calls to memory
464 allocation routines. The first page is used, the rest go onto the
465 free list. This cannot be larger than HOST_BITS_PER_INT for the
466 in_use bitmask for page_group. Hosts that need a different value
467 can override this by defining GGC_QUIRE_SIZE explicitly. */
468 #ifndef GGC_QUIRE_SIZE
470 # define GGC_QUIRE_SIZE 256
472 # define GGC_QUIRE_SIZE 16
476 /* Initial guess as to how many page table entries we might need. */
477 #define INITIAL_PTE_COUNT 128
479 static int ggc_allocated_p (const void *);
480 static page_entry *lookup_page_table_entry (const void *);
481 static void set_page_table_entry (void *, page_entry *);
483 static char *alloc_anon (char *, size_t);
485 #ifdef USING_MALLOC_PAGE_GROUPS
486 static size_t page_group_index (char *, char *);
487 static void set_page_group_in_use (page_group *, char *);
488 static void clear_page_group_in_use (page_group *, char *);
490 static struct page_entry * alloc_page (unsigned);
491 static void free_page (struct page_entry *);
492 static void release_pages (void);
493 static void clear_marks (void);
494 static void sweep_pages (void);
495 static void ggc_recalculate_in_use_p (page_entry *);
496 static void compute_inverse (unsigned);
497 static inline void adjust_depth (void);
498 static void move_ptes_to_front (int, int);
500 void debug_print_page_list (int);
501 static void push_depth (unsigned int);
502 static void push_by_depth (page_entry *, unsigned long *);
504 /* Push an entry onto G.depth. */
507 push_depth (unsigned int i)
509 if (G.depth_in_use >= G.depth_max)
512 G.depth = xrealloc (G.depth, G.depth_max * sizeof (unsigned int));
514 G.depth[G.depth_in_use++] = i;
517 /* Push an entry onto G.by_depth and G.save_in_use. */
520 push_by_depth (page_entry *p, unsigned long *s)
522 if (G.by_depth_in_use >= G.by_depth_max)
525 G.by_depth = xrealloc (G.by_depth,
526 G.by_depth_max * sizeof (page_entry *));
527 G.save_in_use = xrealloc (G.save_in_use,
528 G.by_depth_max * sizeof (unsigned long *));
530 G.by_depth[G.by_depth_in_use] = p;
531 G.save_in_use[G.by_depth_in_use++] = s;
534 #if (GCC_VERSION < 3001)
535 #define prefetch(X) ((void) X)
537 #define prefetch(X) __builtin_prefetch (X)
540 #define save_in_use_p_i(__i) \
542 #define save_in_use_p(__p) \
543 (save_in_use_p_i (__p->index_by_depth))
545 /* Returns nonzero if P was allocated in GC'able memory. */
548 ggc_allocated_p (const void *p)
553 #if HOST_BITS_PER_PTR <= 32
556 page_table table = G.lookup;
557 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
562 if (table->high_bits == high_bits)
566 base = &table->table[0];
569 /* Extract the level 1 and 2 indices. */
573 return base[L1] && base[L1][L2];
576 /* Traverse the page table and find the entry for a page.
577 Die (probably) if the object wasn't allocated via GC. */
579 static inline page_entry *
580 lookup_page_table_entry (const void *p)
585 #if HOST_BITS_PER_PTR <= 32
588 page_table table = G.lookup;
589 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
590 while (table->high_bits != high_bits)
592 base = &table->table[0];
595 /* Extract the level 1 and 2 indices. */
602 /* Set the page table entry for a page. */
605 set_page_table_entry (void *p, page_entry *entry)
610 #if HOST_BITS_PER_PTR <= 32
614 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
615 for (table = G.lookup; table; table = table->next)
616 if (table->high_bits == high_bits)
619 /* Not found -- allocate a new table. */
620 table = xcalloc (1, sizeof(*table));
621 table->next = G.lookup;
622 table->high_bits = high_bits;
625 base = &table->table[0];
628 /* Extract the level 1 and 2 indices. */
632 if (base[L1] == NULL)
633 base[L1] = XCNEWVEC (page_entry *, PAGE_L2_SIZE);
635 base[L1][L2] = entry;
638 /* Prints the page-entry for object size ORDER, for debugging. */
641 debug_print_page_list (int order)
644 printf ("Head=%p, Tail=%p:\n", (void *) G.pages[order],
645 (void *) G.page_tails[order]);
649 printf ("%p(%1d|%3d) -> ", (void *) p, p->context_depth,
650 p->num_free_objects);
658 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
659 (if non-null). The ifdef structure here is intended to cause a
660 compile error unless exactly one of the HAVE_* is defined. */
663 alloc_anon (char *pref ATTRIBUTE_UNUSED, size_t size)
665 #ifdef HAVE_MMAP_ANON
666 char *page = mmap (pref, size, PROT_READ | PROT_WRITE,
667 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
669 #ifdef HAVE_MMAP_DEV_ZERO
670 char *page = mmap (pref, size, PROT_READ | PROT_WRITE,
671 MAP_PRIVATE, G.dev_zero_fd, 0);
674 if (page == (char *) MAP_FAILED)
676 perror ("virtual memory exhausted");
677 exit (FATAL_EXIT_CODE);
680 /* Remember that we allocated this memory. */
681 G.bytes_mapped += size;
683 /* Pretend we don't have access to the allocated pages. We'll enable
684 access to smaller pieces of the area in ggc_alloc. Discard the
685 handle to avoid handle leak. */
686 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (page, size));
691 #ifdef USING_MALLOC_PAGE_GROUPS
692 /* Compute the index for this page into the page group. */
695 page_group_index (char *allocation, char *page)
697 return (size_t) (page - allocation) >> G.lg_pagesize;
700 /* Set and clear the in_use bit for this page in the page group. */
703 set_page_group_in_use (page_group *group, char *page)
705 group->in_use |= 1 << page_group_index (group->allocation, page);
709 clear_page_group_in_use (page_group *group, char *page)
711 group->in_use &= ~(1 << page_group_index (group->allocation, page));
715 /* Allocate a new page for allocating objects of size 2^ORDER,
716 and return an entry for it. The entry is not added to the
717 appropriate page_table list. */
719 static inline struct page_entry *
720 alloc_page (unsigned order)
722 struct page_entry *entry, *p, **pp;
726 size_t page_entry_size;
728 #ifdef USING_MALLOC_PAGE_GROUPS
732 num_objects = OBJECTS_PER_PAGE (order);
733 bitmap_size = BITMAP_SIZE (num_objects + 1);
734 page_entry_size = sizeof (page_entry) - sizeof (long) + bitmap_size;
735 entry_size = num_objects * OBJECT_SIZE (order);
736 if (entry_size < G.pagesize)
737 entry_size = G.pagesize;
742 /* Check the list of free pages for one we can use. */
743 for (pp = &G.free_pages, p = *pp; p; pp = &p->next, p = *pp)
744 if (p->bytes == entry_size)
749 /* Recycle the allocated memory from this page ... */
753 #ifdef USING_MALLOC_PAGE_GROUPS
757 /* ... and, if possible, the page entry itself. */
758 if (p->order == order)
761 memset (entry, 0, page_entry_size);
767 else if (entry_size == G.pagesize)
769 /* We want just one page. Allocate a bunch of them and put the
770 extras on the freelist. (Can only do this optimization with
771 mmap for backing store.) */
772 struct page_entry *e, *f = G.free_pages;
775 page = alloc_anon (NULL, G.pagesize * GGC_QUIRE_SIZE);
777 /* This loop counts down so that the chain will be in ascending
779 for (i = GGC_QUIRE_SIZE - 1; i >= 1; i--)
781 e = xcalloc (1, page_entry_size);
783 e->bytes = G.pagesize;
784 e->page = page + (i << G.lg_pagesize);
792 page = alloc_anon (NULL, entry_size);
794 #ifdef USING_MALLOC_PAGE_GROUPS
797 /* Allocate a large block of memory and serve out the aligned
798 pages therein. This results in much less memory wastage
799 than the traditional implementation of valloc. */
801 char *allocation, *a, *enda;
802 size_t alloc_size, head_slop, tail_slop;
803 int multiple_pages = (entry_size == G.pagesize);
806 alloc_size = GGC_QUIRE_SIZE * G.pagesize;
808 alloc_size = entry_size + G.pagesize - 1;
809 allocation = xmalloc (alloc_size);
811 page = (char *) (((size_t) allocation + G.pagesize - 1) & -G.pagesize);
812 head_slop = page - allocation;
814 tail_slop = ((size_t) allocation + alloc_size) & (G.pagesize - 1);
816 tail_slop = alloc_size - entry_size - head_slop;
817 enda = allocation + alloc_size - tail_slop;
819 /* We allocated N pages, which are likely not aligned, leaving
820 us with N-1 usable pages. We plan to place the page_group
821 structure somewhere in the slop. */
822 if (head_slop >= sizeof (page_group))
823 group = (page_group *)page - 1;
826 /* We magically got an aligned allocation. Too bad, we have
827 to waste a page anyway. */
831 tail_slop += G.pagesize;
833 gcc_assert (tail_slop >= sizeof (page_group));
834 group = (page_group *)enda;
835 tail_slop -= sizeof (page_group);
838 /* Remember that we allocated this memory. */
839 group->next = G.page_groups;
840 group->allocation = allocation;
841 group->alloc_size = alloc_size;
843 G.page_groups = group;
844 G.bytes_mapped += alloc_size;
846 /* If we allocated multiple pages, put the rest on the free list. */
849 struct page_entry *e, *f = G.free_pages;
850 for (a = enda - G.pagesize; a != page; a -= G.pagesize)
852 e = xcalloc (1, page_entry_size);
854 e->bytes = G.pagesize;
866 entry = xcalloc (1, page_entry_size);
868 entry->bytes = entry_size;
870 entry->context_depth = G.context_depth;
871 entry->order = order;
872 entry->num_free_objects = num_objects;
873 entry->next_bit_hint = 1;
875 G.context_depth_allocations |= (unsigned long)1 << G.context_depth;
877 #ifdef USING_MALLOC_PAGE_GROUPS
878 entry->group = group;
879 set_page_group_in_use (group, page);
882 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
883 increment the hint. */
884 entry->in_use_p[num_objects / HOST_BITS_PER_LONG]
885 = (unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG);
887 set_page_table_entry (page, entry);
889 if (GGC_DEBUG_LEVEL >= 2)
890 fprintf (G.debug_file,
891 "Allocating page at %p, object size=%lu, data %p-%p\n",
892 (void *) entry, (unsigned long) OBJECT_SIZE (order), page,
893 page + entry_size - 1);
898 /* Adjust the size of G.depth so that no index greater than the one
899 used by the top of the G.by_depth is used. */
906 if (G.by_depth_in_use)
908 top = G.by_depth[G.by_depth_in_use-1];
910 /* Peel back indices in depth that index into by_depth, so that
911 as new elements are added to by_depth, we note the indices
912 of those elements, if they are for new context depths. */
913 while (G.depth_in_use > (size_t)top->context_depth+1)
918 /* For a page that is no longer needed, put it on the free page list. */
921 free_page (page_entry *entry)
923 if (GGC_DEBUG_LEVEL >= 2)
924 fprintf (G.debug_file,
925 "Deallocating page at %p, data %p-%p\n", (void *) entry,
926 entry->page, entry->page + entry->bytes - 1);
928 /* Mark the page as inaccessible. Discard the handle to avoid handle
930 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (entry->page, entry->bytes));
932 set_page_table_entry (entry->page, NULL);
934 #ifdef USING_MALLOC_PAGE_GROUPS
935 clear_page_group_in_use (entry->group, entry->page);
938 if (G.by_depth_in_use > 1)
940 page_entry *top = G.by_depth[G.by_depth_in_use-1];
941 int i = entry->index_by_depth;
943 /* We cannot free a page from a context deeper than the current
945 gcc_assert (entry->context_depth == top->context_depth);
947 /* Put top element into freed slot. */
949 G.save_in_use[i] = G.save_in_use[G.by_depth_in_use-1];
950 top->index_by_depth = i;
956 entry->next = G.free_pages;
957 G.free_pages = entry;
960 /* Release the free page cache to the system. */
966 page_entry *p, *next;
970 /* Gather up adjacent pages so they are unmapped together. */
981 while (p && p->page == start + len)
990 G.bytes_mapped -= len;
995 #ifdef USING_MALLOC_PAGE_GROUPS
999 /* Remove all pages from free page groups from the list. */
1001 while ((p = *pp) != NULL)
1002 if (p->group->in_use == 0)
1010 /* Remove all free page groups, and release the storage. */
1011 gp = &G.page_groups;
1012 while ((g = *gp) != NULL)
1016 G.bytes_mapped -= g->alloc_size;
1017 free (g->allocation);
1024 /* This table provides a fast way to determine ceil(log_2(size)) for
1025 allocation requests. The minimum allocation size is eight bytes. */
1027 static unsigned char size_lookup[511] =
1029 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
1030 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
1031 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1032 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1033 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1034 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1035 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1036 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1037 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1038 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1039 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1040 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1041 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1042 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1043 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1044 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1045 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1046 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1047 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1048 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1049 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1050 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1051 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1052 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1053 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1054 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1055 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1056 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1057 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1058 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1059 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
1060 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9
1063 /* Typed allocation function. Does nothing special in this collector. */
1066 ggc_alloc_typed_stat (enum gt_types_enum type ATTRIBUTE_UNUSED, size_t size
1069 return ggc_alloc_stat (size PASS_MEM_STAT);
1072 /* Allocate a chunk of memory of SIZE bytes. Its contents are undefined. */
1075 ggc_alloc_stat (size_t size MEM_STAT_DECL)
1077 size_t order, word, bit, object_offset, object_size;
1078 struct page_entry *entry;
1083 order = size_lookup[size];
1084 object_size = OBJECT_SIZE (order);
1089 while (size > (object_size = OBJECT_SIZE (order)))
1093 /* If there are non-full pages for this size allocation, they are at
1094 the head of the list. */
1095 entry = G.pages[order];
1097 /* If there is no page for this object size, or all pages in this
1098 context are full, allocate a new page. */
1099 if (entry == NULL || entry->num_free_objects == 0)
1101 struct page_entry *new_entry;
1102 new_entry = alloc_page (order);
1104 new_entry->index_by_depth = G.by_depth_in_use;
1105 push_by_depth (new_entry, 0);
1107 /* We can skip context depths, if we do, make sure we go all the
1108 way to the new depth. */
1109 while (new_entry->context_depth >= G.depth_in_use)
1110 push_depth (G.by_depth_in_use-1);
1112 /* If this is the only entry, it's also the tail. If it is not
1113 the only entry, then we must update the PREV pointer of the
1114 ENTRY (G.pages[order]) to point to our new page entry. */
1116 G.page_tails[order] = new_entry;
1118 entry->prev = new_entry;
1120 /* Put new pages at the head of the page list. By definition the
1121 entry at the head of the list always has a NULL pointer. */
1122 new_entry->next = entry;
1123 new_entry->prev = NULL;
1125 G.pages[order] = new_entry;
1127 /* For a new page, we know the word and bit positions (in the
1128 in_use bitmap) of the first available object -- they're zero. */
1129 new_entry->next_bit_hint = 1;
1136 /* First try to use the hint left from the previous allocation
1137 to locate a clear bit in the in-use bitmap. We've made sure
1138 that the one-past-the-end bit is always set, so if the hint
1139 has run over, this test will fail. */
1140 unsigned hint = entry->next_bit_hint;
1141 word = hint / HOST_BITS_PER_LONG;
1142 bit = hint % HOST_BITS_PER_LONG;
1144 /* If the hint didn't work, scan the bitmap from the beginning. */
1145 if ((entry->in_use_p[word] >> bit) & 1)
1148 while (~entry->in_use_p[word] == 0)
1151 #if GCC_VERSION >= 3004
1152 bit = __builtin_ctzl (~entry->in_use_p[word]);
1154 while ((entry->in_use_p[word] >> bit) & 1)
1158 hint = word * HOST_BITS_PER_LONG + bit;
1161 /* Next time, try the next bit. */
1162 entry->next_bit_hint = hint + 1;
1164 object_offset = hint * object_size;
1167 /* Set the in-use bit. */
1168 entry->in_use_p[word] |= ((unsigned long) 1 << bit);
1170 /* Keep a running total of the number of free objects. If this page
1171 fills up, we may have to move it to the end of the list if the
1172 next page isn't full. If the next page is full, all subsequent
1173 pages are full, so there's no need to move it. */
1174 if (--entry->num_free_objects == 0
1175 && entry->next != NULL
1176 && entry->next->num_free_objects > 0)
1178 /* We have a new head for the list. */
1179 G.pages[order] = entry->next;
1181 /* We are moving ENTRY to the end of the page table list.
1182 The new page at the head of the list will have NULL in
1183 its PREV field and ENTRY will have NULL in its NEXT field. */
1184 entry->next->prev = NULL;
1187 /* Append ENTRY to the tail of the list. */
1188 entry->prev = G.page_tails[order];
1189 G.page_tails[order]->next = entry;
1190 G.page_tails[order] = entry;
1193 /* Calculate the object's address. */
1194 result = entry->page + object_offset;
1195 #ifdef GATHER_STATISTICS
1196 ggc_record_overhead (OBJECT_SIZE (order), OBJECT_SIZE (order) - size,
1197 result PASS_MEM_STAT);
1200 #ifdef ENABLE_GC_CHECKING
1201 /* Keep poisoning-by-writing-0xaf the object, in an attempt to keep the
1202 exact same semantics in presence of memory bugs, regardless of
1203 ENABLE_VALGRIND_CHECKING. We override this request below. Drop the
1204 handle to avoid handle leak. */
1205 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (result, object_size));
1207 /* `Poison' the entire allocated object, including any padding at
1209 memset (result, 0xaf, object_size);
1211 /* Make the bytes after the end of the object unaccessible. Discard the
1212 handle to avoid handle leak. */
1213 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS ((char *) result + size,
1214 object_size - size));
1217 /* Tell Valgrind that the memory is there, but its content isn't
1218 defined. The bytes at the end of the object are still marked
1220 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (result, size));
1222 /* Keep track of how many bytes are being allocated. This
1223 information is used in deciding when to collect. */
1224 G.allocated += object_size;
1226 /* For timevar statistics. */
1227 timevar_ggc_mem_total += object_size;
1229 #ifdef GATHER_STATISTICS
1231 size_t overhead = object_size - size;
1233 G.stats.total_overhead += overhead;
1234 G.stats.total_allocated += object_size;
1235 G.stats.total_overhead_per_order[order] += overhead;
1236 G.stats.total_allocated_per_order[order] += object_size;
1240 G.stats.total_overhead_under32 += overhead;
1241 G.stats.total_allocated_under32 += object_size;
1245 G.stats.total_overhead_under64 += overhead;
1246 G.stats.total_allocated_under64 += object_size;
1250 G.stats.total_overhead_under128 += overhead;
1251 G.stats.total_allocated_under128 += object_size;
1256 if (GGC_DEBUG_LEVEL >= 3)
1257 fprintf (G.debug_file,
1258 "Allocating object, requested size=%lu, actual=%lu at %p on %p\n",
1259 (unsigned long) size, (unsigned long) object_size, result,
1265 /* If P is not marked, marks it and return false. Otherwise return true.
1266 P must have been allocated by the GC allocator; it mustn't point to
1267 static objects, stack variables, or memory allocated with malloc. */
1270 ggc_set_mark (const void *p)
1276 /* Look up the page on which the object is alloced. If the object
1277 wasn't allocated by the collector, we'll probably die. */
1278 entry = lookup_page_table_entry (p);
1281 /* Calculate the index of the object on the page; this is its bit
1282 position in the in_use_p bitmap. */
1283 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1284 word = bit / HOST_BITS_PER_LONG;
1285 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1287 /* If the bit was previously set, skip it. */
1288 if (entry->in_use_p[word] & mask)
1291 /* Otherwise set it, and decrement the free object count. */
1292 entry->in_use_p[word] |= mask;
1293 entry->num_free_objects -= 1;
1295 if (GGC_DEBUG_LEVEL >= 4)
1296 fprintf (G.debug_file, "Marking %p\n", p);
1301 /* Return 1 if P has been marked, zero otherwise.
1302 P must have been allocated by the GC allocator; it mustn't point to
1303 static objects, stack variables, or memory allocated with malloc. */
1306 ggc_marked_p (const void *p)
1312 /* Look up the page on which the object is alloced. If the object
1313 wasn't allocated by the collector, we'll probably die. */
1314 entry = lookup_page_table_entry (p);
1317 /* Calculate the index of the object on the page; this is its bit
1318 position in the in_use_p bitmap. */
1319 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1320 word = bit / HOST_BITS_PER_LONG;
1321 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1323 return (entry->in_use_p[word] & mask) != 0;
1326 /* Return the size of the gc-able object P. */
1329 ggc_get_size (const void *p)
1331 page_entry *pe = lookup_page_table_entry (p);
1332 return OBJECT_SIZE (pe->order);
1335 /* Release the memory for object P. */
1340 page_entry *pe = lookup_page_table_entry (p);
1341 size_t order = pe->order;
1342 size_t size = OBJECT_SIZE (order);
1344 #ifdef GATHER_STATISTICS
1345 ggc_free_overhead (p);
1348 if (GGC_DEBUG_LEVEL >= 3)
1349 fprintf (G.debug_file,
1350 "Freeing object, actual size=%lu, at %p on %p\n",
1351 (unsigned long) size, p, (void *) pe);
1353 #ifdef ENABLE_GC_CHECKING
1354 /* Poison the data, to indicate the data is garbage. */
1355 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (p, size));
1356 memset (p, 0xa5, size);
1358 /* Let valgrind know the object is free. */
1359 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (p, size));
1361 #ifdef ENABLE_GC_ALWAYS_COLLECT
1362 /* In the completely-anal-checking mode, we do *not* immediately free
1363 the data, but instead verify that the data is *actually* not
1364 reachable the next time we collect. */
1366 struct free_object *fo = XNEW (struct free_object);
1368 fo->next = G.free_object_list;
1369 G.free_object_list = fo;
1373 unsigned int bit_offset, word, bit;
1375 G.allocated -= size;
1377 /* Mark the object not-in-use. */
1378 bit_offset = OFFSET_TO_BIT (((const char *) p) - pe->page, order);
1379 word = bit_offset / HOST_BITS_PER_LONG;
1380 bit = bit_offset % HOST_BITS_PER_LONG;
1381 pe->in_use_p[word] &= ~(1UL << bit);
1383 if (pe->num_free_objects++ == 0)
1387 /* If the page is completely full, then it's supposed to
1388 be after all pages that aren't. Since we've freed one
1389 object from a page that was full, we need to move the
1390 page to the head of the list.
1392 PE is the node we want to move. Q is the previous node
1393 and P is the next node in the list. */
1395 if (q && q->num_free_objects == 0)
1401 /* If PE was at the end of the list, then Q becomes the
1402 new end of the list. If PE was not the end of the
1403 list, then we need to update the PREV field for P. */
1405 G.page_tails[order] = q;
1409 /* Move PE to the head of the list. */
1410 pe->next = G.pages[order];
1412 G.pages[order]->prev = pe;
1413 G.pages[order] = pe;
1416 /* Reset the hint bit to point to the only free object. */
1417 pe->next_bit_hint = bit_offset;
1423 /* Subroutine of init_ggc which computes the pair of numbers used to
1424 perform division by OBJECT_SIZE (order) and fills in inverse_table[].
1426 This algorithm is taken from Granlund and Montgomery's paper
1427 "Division by Invariant Integers using Multiplication"
1428 (Proc. SIGPLAN PLDI, 1994), section 9 (Exact division by
1432 compute_inverse (unsigned order)
1437 size = OBJECT_SIZE (order);
1439 while (size % 2 == 0)
1446 while (inv * size != 1)
1447 inv = inv * (2 - inv*size);
1449 DIV_MULT (order) = inv;
1450 DIV_SHIFT (order) = e;
1453 /* Initialize the ggc-mmap allocator. */
1459 G.pagesize = getpagesize();
1460 G.lg_pagesize = exact_log2 (G.pagesize);
1462 #ifdef HAVE_MMAP_DEV_ZERO
1463 G.dev_zero_fd = open ("/dev/zero", O_RDONLY);
1464 if (G.dev_zero_fd == -1)
1465 internal_error ("open /dev/zero: %m");
1469 G.debug_file = fopen ("ggc-mmap.debug", "w");
1471 G.debug_file = stdout;
1475 /* StunOS has an amazing off-by-one error for the first mmap allocation
1476 after fiddling with RLIMIT_STACK. The result, as hard as it is to
1477 believe, is an unaligned page allocation, which would cause us to
1478 hork badly if we tried to use it. */
1480 char *p = alloc_anon (NULL, G.pagesize);
1481 struct page_entry *e;
1482 if ((size_t)p & (G.pagesize - 1))
1484 /* How losing. Discard this one and try another. If we still
1485 can't get something useful, give up. */
1487 p = alloc_anon (NULL, G.pagesize);
1488 gcc_assert (!((size_t)p & (G.pagesize - 1)));
1491 /* We have a good page, might as well hold onto it... */
1492 e = XCNEW (struct page_entry);
1493 e->bytes = G.pagesize;
1495 e->next = G.free_pages;
1500 /* Initialize the object size table. */
1501 for (order = 0; order < HOST_BITS_PER_PTR; ++order)
1502 object_size_table[order] = (size_t) 1 << order;
1503 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1505 size_t s = extra_order_size_table[order - HOST_BITS_PER_PTR];
1507 /* If S is not a multiple of the MAX_ALIGNMENT, then round it up
1508 so that we're sure of getting aligned memory. */
1509 s = ROUND_UP (s, MAX_ALIGNMENT);
1510 object_size_table[order] = s;
1513 /* Initialize the objects-per-page and inverse tables. */
1514 for (order = 0; order < NUM_ORDERS; ++order)
1516 objects_per_page_table[order] = G.pagesize / OBJECT_SIZE (order);
1517 if (objects_per_page_table[order] == 0)
1518 objects_per_page_table[order] = 1;
1519 compute_inverse (order);
1522 /* Reset the size_lookup array to put appropriately sized objects in
1523 the special orders. All objects bigger than the previous power
1524 of two, but no greater than the special size, should go in the
1526 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1531 o = size_lookup[OBJECT_SIZE (order)];
1532 for (i = OBJECT_SIZE (order); size_lookup [i] == o; --i)
1533 size_lookup[i] = order;
1538 G.depth = XNEWVEC (unsigned int, G.depth_max);
1540 G.by_depth_in_use = 0;
1541 G.by_depth_max = INITIAL_PTE_COUNT;
1542 G.by_depth = XNEWVEC (page_entry *, G.by_depth_max);
1543 G.save_in_use = XNEWVEC (unsigned long *, G.by_depth_max);
1546 /* Start a new GGC zone. */
1549 new_ggc_zone (const char *name ATTRIBUTE_UNUSED)
1554 /* Destroy a GGC zone. */
1556 destroy_ggc_zone (struct alloc_zone *zone ATTRIBUTE_UNUSED)
1560 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
1561 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
1564 ggc_recalculate_in_use_p (page_entry *p)
1569 /* Because the past-the-end bit in in_use_p is always set, we
1570 pretend there is one additional object. */
1571 num_objects = OBJECTS_IN_PAGE (p) + 1;
1573 /* Reset the free object count. */
1574 p->num_free_objects = num_objects;
1576 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
1578 i < CEIL (BITMAP_SIZE (num_objects),
1579 sizeof (*p->in_use_p));
1584 /* Something is in use if it is marked, or if it was in use in a
1585 context further down the context stack. */
1586 p->in_use_p[i] |= save_in_use_p (p)[i];
1588 /* Decrement the free object count for every object allocated. */
1589 for (j = p->in_use_p[i]; j; j >>= 1)
1590 p->num_free_objects -= (j & 1);
1593 gcc_assert (p->num_free_objects < num_objects);
1596 /* Unmark all objects. */
1603 for (order = 2; order < NUM_ORDERS; order++)
1607 for (p = G.pages[order]; p != NULL; p = p->next)
1609 size_t num_objects = OBJECTS_IN_PAGE (p);
1610 size_t bitmap_size = BITMAP_SIZE (num_objects + 1);
1612 /* The data should be page-aligned. */
1613 gcc_assert (!((size_t) p->page & (G.pagesize - 1)));
1615 /* Pages that aren't in the topmost context are not collected;
1616 nevertheless, we need their in-use bit vectors to store GC
1617 marks. So, back them up first. */
1618 if (p->context_depth < G.context_depth)
1620 if (! save_in_use_p (p))
1621 save_in_use_p (p) = xmalloc (bitmap_size);
1622 memcpy (save_in_use_p (p), p->in_use_p, bitmap_size);
1625 /* Reset reset the number of free objects and clear the
1626 in-use bits. These will be adjusted by mark_obj. */
1627 p->num_free_objects = num_objects;
1628 memset (p->in_use_p, 0, bitmap_size);
1630 /* Make sure the one-past-the-end bit is always set. */
1631 p->in_use_p[num_objects / HOST_BITS_PER_LONG]
1632 = ((unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG));
1637 /* Free all empty pages. Partially empty pages need no attention
1638 because the `mark' bit doubles as an `unused' bit. */
1645 for (order = 2; order < NUM_ORDERS; order++)
1647 /* The last page-entry to consider, regardless of entries
1648 placed at the end of the list. */
1649 page_entry * const last = G.page_tails[order];
1652 size_t live_objects;
1653 page_entry *p, *previous;
1663 page_entry *next = p->next;
1665 /* Loop until all entries have been examined. */
1668 num_objects = OBJECTS_IN_PAGE (p);
1670 /* Add all live objects on this page to the count of
1671 allocated memory. */
1672 live_objects = num_objects - p->num_free_objects;
1674 G.allocated += OBJECT_SIZE (order) * live_objects;
1676 /* Only objects on pages in the topmost context should get
1678 if (p->context_depth < G.context_depth)
1681 /* Remove the page if it's empty. */
1682 else if (live_objects == 0)
1684 /* If P was the first page in the list, then NEXT
1685 becomes the new first page in the list, otherwise
1686 splice P out of the forward pointers. */
1688 G.pages[order] = next;
1690 previous->next = next;
1692 /* Splice P out of the back pointers too. */
1694 next->prev = previous;
1696 /* Are we removing the last element? */
1697 if (p == G.page_tails[order])
1698 G.page_tails[order] = previous;
1703 /* If the page is full, move it to the end. */
1704 else if (p->num_free_objects == 0)
1706 /* Don't move it if it's already at the end. */
1707 if (p != G.page_tails[order])
1709 /* Move p to the end of the list. */
1711 p->prev = G.page_tails[order];
1712 G.page_tails[order]->next = p;
1714 /* Update the tail pointer... */
1715 G.page_tails[order] = p;
1717 /* ... and the head pointer, if necessary. */
1719 G.pages[order] = next;
1721 previous->next = next;
1723 /* And update the backpointer in NEXT if necessary. */
1725 next->prev = previous;
1731 /* If we've fallen through to here, it's a page in the
1732 topmost context that is neither full nor empty. Such a
1733 page must precede pages at lesser context depth in the
1734 list, so move it to the head. */
1735 else if (p != G.pages[order])
1737 previous->next = p->next;
1739 /* Update the backchain in the next node if it exists. */
1741 p->next->prev = previous;
1743 /* Move P to the head of the list. */
1744 p->next = G.pages[order];
1746 G.pages[order]->prev = p;
1748 /* Update the head pointer. */
1751 /* Are we moving the last element? */
1752 if (G.page_tails[order] == p)
1753 G.page_tails[order] = previous;
1762 /* Now, restore the in_use_p vectors for any pages from contexts
1763 other than the current one. */
1764 for (p = G.pages[order]; p; p = p->next)
1765 if (p->context_depth != G.context_depth)
1766 ggc_recalculate_in_use_p (p);
1770 #ifdef ENABLE_GC_CHECKING
1771 /* Clobber all free objects. */
1778 for (order = 2; order < NUM_ORDERS; order++)
1780 size_t size = OBJECT_SIZE (order);
1783 for (p = G.pages[order]; p != NULL; p = p->next)
1788 if (p->context_depth != G.context_depth)
1789 /* Since we don't do any collection for pages in pushed
1790 contexts, there's no need to do any poisoning. And
1791 besides, the IN_USE_P array isn't valid until we pop
1795 num_objects = OBJECTS_IN_PAGE (p);
1796 for (i = 0; i < num_objects; i++)
1799 word = i / HOST_BITS_PER_LONG;
1800 bit = i % HOST_BITS_PER_LONG;
1801 if (((p->in_use_p[word] >> bit) & 1) == 0)
1803 char *object = p->page + i * size;
1805 /* Keep poison-by-write when we expect to use Valgrind,
1806 so the exact same memory semantics is kept, in case
1807 there are memory errors. We override this request
1809 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (object, size));
1810 memset (object, 0xa5, size);
1812 /* Drop the handle to avoid handle leak. */
1813 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (object, size));
1820 #define poison_pages()
1823 #ifdef ENABLE_GC_ALWAYS_COLLECT
1824 /* Validate that the reportedly free objects actually are. */
1827 validate_free_objects (void)
1829 struct free_object *f, *next, *still_free = NULL;
1831 for (f = G.free_object_list; f ; f = next)
1833 page_entry *pe = lookup_page_table_entry (f->object);
1836 bit = OFFSET_TO_BIT ((char *)f->object - pe->page, pe->order);
1837 word = bit / HOST_BITS_PER_LONG;
1838 bit = bit % HOST_BITS_PER_LONG;
1841 /* Make certain it isn't visible from any root. Notice that we
1842 do this check before sweep_pages merges save_in_use_p. */
1843 gcc_assert (!(pe->in_use_p[word] & (1UL << bit)));
1845 /* If the object comes from an outer context, then retain the
1846 free_object entry, so that we can verify that the address
1847 isn't live on the stack in some outer context. */
1848 if (pe->context_depth != G.context_depth)
1850 f->next = still_free;
1857 G.free_object_list = still_free;
1860 #define validate_free_objects()
1863 /* Top level mark-and-sweep routine. */
1868 /* Avoid frequent unnecessary work by skipping collection if the
1869 total allocations haven't expanded much since the last
1871 float allocated_last_gc =
1872 MAX (G.allocated_last_gc, (size_t)PARAM_VALUE (GGC_MIN_HEAPSIZE) * 1024);
1874 float min_expand = allocated_last_gc * PARAM_VALUE (GGC_MIN_EXPAND) / 100;
1876 if (G.allocated < allocated_last_gc + min_expand && !ggc_force_collect)
1879 timevar_push (TV_GC);
1881 fprintf (stderr, " {GC %luk -> ", (unsigned long) G.allocated / 1024);
1882 if (GGC_DEBUG_LEVEL >= 2)
1883 fprintf (G.debug_file, "BEGIN COLLECTING\n");
1885 /* Zero the total allocated bytes. This will be recalculated in the
1889 /* Release the pages we freed the last time we collected, but didn't
1890 reuse in the interim. */
1893 /* Indicate that we've seen collections at this context depth. */
1894 G.context_depth_collections = ((unsigned long)1 << (G.context_depth + 1)) - 1;
1898 #ifdef GATHER_STATISTICS
1899 ggc_prune_overhead_list ();
1902 validate_free_objects ();
1905 G.allocated_last_gc = G.allocated;
1907 timevar_pop (TV_GC);
1910 fprintf (stderr, "%luk}", (unsigned long) G.allocated / 1024);
1911 if (GGC_DEBUG_LEVEL >= 2)
1912 fprintf (G.debug_file, "END COLLECTING\n");
1915 /* Print allocation statistics. */
1916 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \
1918 : ((x) < 1024*1024*10 \
1920 : (x) / (1024*1024))))
1921 #define STAT_LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
1924 ggc_print_statistics (void)
1926 struct ggc_statistics stats;
1928 size_t total_overhead = 0;
1930 /* Clear the statistics. */
1931 memset (&stats, 0, sizeof (stats));
1933 /* Make sure collection will really occur. */
1934 G.allocated_last_gc = 0;
1936 /* Collect and print the statistics common across collectors. */
1937 ggc_print_common_statistics (stderr, &stats);
1939 /* Release free pages so that we will not count the bytes allocated
1940 there as part of the total allocated memory. */
1943 /* Collect some information about the various sizes of
1946 "Memory still allocated at the end of the compilation process\n");
1947 fprintf (stderr, "%-5s %10s %10s %10s\n",
1948 "Size", "Allocated", "Used", "Overhead");
1949 for (i = 0; i < NUM_ORDERS; ++i)
1956 /* Skip empty entries. */
1960 overhead = allocated = in_use = 0;
1962 /* Figure out the total number of bytes allocated for objects of
1963 this size, and how many of them are actually in use. Also figure
1964 out how much memory the page table is using. */
1965 for (p = G.pages[i]; p; p = p->next)
1967 allocated += p->bytes;
1969 (OBJECTS_IN_PAGE (p) - p->num_free_objects) * OBJECT_SIZE (i);
1971 overhead += (sizeof (page_entry) - sizeof (long)
1972 + BITMAP_SIZE (OBJECTS_IN_PAGE (p) + 1));
1974 fprintf (stderr, "%-5lu %10lu%c %10lu%c %10lu%c\n",
1975 (unsigned long) OBJECT_SIZE (i),
1976 SCALE (allocated), STAT_LABEL (allocated),
1977 SCALE (in_use), STAT_LABEL (in_use),
1978 SCALE (overhead), STAT_LABEL (overhead));
1979 total_overhead += overhead;
1981 fprintf (stderr, "%-5s %10lu%c %10lu%c %10lu%c\n", "Total",
1982 SCALE (G.bytes_mapped), STAT_LABEL (G.bytes_mapped),
1983 SCALE (G.allocated), STAT_LABEL(G.allocated),
1984 SCALE (total_overhead), STAT_LABEL (total_overhead));
1986 #ifdef GATHER_STATISTICS
1988 fprintf (stderr, "\nTotal allocations and overheads during the compilation process\n");
1990 fprintf (stderr, "Total Overhead: %10lld\n",
1991 G.stats.total_overhead);
1992 fprintf (stderr, "Total Allocated: %10lld\n",
1993 G.stats.total_allocated);
1995 fprintf (stderr, "Total Overhead under 32B: %10lld\n",
1996 G.stats.total_overhead_under32);
1997 fprintf (stderr, "Total Allocated under 32B: %10lld\n",
1998 G.stats.total_allocated_under32);
1999 fprintf (stderr, "Total Overhead under 64B: %10lld\n",
2000 G.stats.total_overhead_under64);
2001 fprintf (stderr, "Total Allocated under 64B: %10lld\n",
2002 G.stats.total_allocated_under64);
2003 fprintf (stderr, "Total Overhead under 128B: %10lld\n",
2004 G.stats.total_overhead_under128);
2005 fprintf (stderr, "Total Allocated under 128B: %10lld\n",
2006 G.stats.total_allocated_under128);
2008 for (i = 0; i < NUM_ORDERS; i++)
2009 if (G.stats.total_allocated_per_order[i])
2011 fprintf (stderr, "Total Overhead page size %7d: %10lld\n",
2012 OBJECT_SIZE (i), G.stats.total_overhead_per_order[i]);
2013 fprintf (stderr, "Total Allocated page size %7d: %10lld\n",
2014 OBJECT_SIZE (i), G.stats.total_allocated_per_order[i]);
2022 struct ggc_pch_ondisk
2024 unsigned totals[NUM_ORDERS];
2026 size_t base[NUM_ORDERS];
2027 size_t written[NUM_ORDERS];
2030 struct ggc_pch_data *
2033 return XCNEW (struct ggc_pch_data);
2037 ggc_pch_count_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2038 size_t size, bool is_string ATTRIBUTE_UNUSED,
2039 enum gt_types_enum type ATTRIBUTE_UNUSED)
2044 order = size_lookup[size];
2048 while (size > OBJECT_SIZE (order))
2052 d->d.totals[order]++;
2056 ggc_pch_total_size (struct ggc_pch_data *d)
2061 for (i = 0; i < NUM_ORDERS; i++)
2062 a += ROUND_UP (d->d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2067 ggc_pch_this_base (struct ggc_pch_data *d, void *base)
2069 size_t a = (size_t) base;
2072 for (i = 0; i < NUM_ORDERS; i++)
2075 a += ROUND_UP (d->d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2081 ggc_pch_alloc_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2082 size_t size, bool is_string ATTRIBUTE_UNUSED,
2083 enum gt_types_enum type ATTRIBUTE_UNUSED)
2089 order = size_lookup[size];
2093 while (size > OBJECT_SIZE (order))
2097 result = (char *) d->base[order];
2098 d->base[order] += OBJECT_SIZE (order);
2103 ggc_pch_prepare_write (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
2104 FILE *f ATTRIBUTE_UNUSED)
2106 /* Nothing to do. */
2110 ggc_pch_write_object (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
2111 FILE *f, void *x, void *newx ATTRIBUTE_UNUSED,
2112 size_t size, bool is_string ATTRIBUTE_UNUSED)
2115 static const char emptyBytes[256];
2118 order = size_lookup[size];
2122 while (size > OBJECT_SIZE (order))
2126 if (fwrite (x, size, 1, f) != 1)
2127 fatal_error ("can't write PCH file: %m");
2129 /* If SIZE is not the same as OBJECT_SIZE(order), then we need to pad the
2130 object out to OBJECT_SIZE(order). This happens for strings. */
2132 if (size != OBJECT_SIZE (order))
2134 unsigned padding = OBJECT_SIZE(order) - size;
2136 /* To speed small writes, we use a nulled-out array that's larger
2137 than most padding requests as the source for our null bytes. This
2138 permits us to do the padding with fwrite() rather than fseek(), and
2139 limits the chance the OS may try to flush any outstanding writes. */
2140 if (padding <= sizeof(emptyBytes))
2142 if (fwrite (emptyBytes, 1, padding, f) != padding)
2143 fatal_error ("can't write PCH file");
2147 /* Larger than our buffer? Just default to fseek. */
2148 if (fseek (f, padding, SEEK_CUR) != 0)
2149 fatal_error ("can't write PCH file");
2153 d->written[order]++;
2154 if (d->written[order] == d->d.totals[order]
2155 && fseek (f, ROUND_UP_VALUE (d->d.totals[order] * OBJECT_SIZE (order),
2158 fatal_error ("can't write PCH file: %m");
2162 ggc_pch_finish (struct ggc_pch_data *d, FILE *f)
2164 if (fwrite (&d->d, sizeof (d->d), 1, f) != 1)
2165 fatal_error ("can't write PCH file: %m");
2169 /* Move the PCH PTE entries just added to the end of by_depth, to the
2173 move_ptes_to_front (int count_old_page_tables, int count_new_page_tables)
2177 /* First, we swap the new entries to the front of the varrays. */
2178 page_entry **new_by_depth;
2179 unsigned long **new_save_in_use;
2181 new_by_depth = XNEWVEC (page_entry *, G.by_depth_max);
2182 new_save_in_use = XNEWVEC (unsigned long *, G.by_depth_max);
2184 memcpy (&new_by_depth[0],
2185 &G.by_depth[count_old_page_tables],
2186 count_new_page_tables * sizeof (void *));
2187 memcpy (&new_by_depth[count_new_page_tables],
2189 count_old_page_tables * sizeof (void *));
2190 memcpy (&new_save_in_use[0],
2191 &G.save_in_use[count_old_page_tables],
2192 count_new_page_tables * sizeof (void *));
2193 memcpy (&new_save_in_use[count_new_page_tables],
2195 count_old_page_tables * sizeof (void *));
2198 free (G.save_in_use);
2200 G.by_depth = new_by_depth;
2201 G.save_in_use = new_save_in_use;
2203 /* Now update all the index_by_depth fields. */
2204 for (i = G.by_depth_in_use; i > 0; --i)
2206 page_entry *p = G.by_depth[i-1];
2207 p->index_by_depth = i-1;
2210 /* And last, we update the depth pointers in G.depth. The first
2211 entry is already 0, and context 0 entries always start at index
2212 0, so there is nothing to update in the first slot. We need a
2213 second slot, only if we have old ptes, and if we do, they start
2214 at index count_new_page_tables. */
2215 if (count_old_page_tables)
2216 push_depth (count_new_page_tables);
2220 ggc_pch_read (FILE *f, void *addr)
2222 struct ggc_pch_ondisk d;
2225 unsigned long count_old_page_tables;
2226 unsigned long count_new_page_tables;
2228 count_old_page_tables = G.by_depth_in_use;
2230 /* We've just read in a PCH file. So, every object that used to be
2231 allocated is now free. */
2233 #ifdef ENABLE_GC_CHECKING
2237 /* No object read from a PCH file should ever be freed. So, set the
2238 context depth to 1, and set the depth of all the currently-allocated
2239 pages to be 1 too. PCH pages will have depth 0. */
2240 gcc_assert (!G.context_depth);
2241 G.context_depth = 1;
2242 for (i = 0; i < NUM_ORDERS; i++)
2245 for (p = G.pages[i]; p != NULL; p = p->next)
2246 p->context_depth = G.context_depth;
2249 /* Allocate the appropriate page-table entries for the pages read from
2251 if (fread (&d, sizeof (d), 1, f) != 1)
2252 fatal_error ("can't read PCH file: %m");
2254 for (i = 0; i < NUM_ORDERS; i++)
2256 struct page_entry *entry;
2262 if (d.totals[i] == 0)
2265 bytes = ROUND_UP (d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2266 num_objs = bytes / OBJECT_SIZE (i);
2267 entry = xcalloc (1, (sizeof (struct page_entry)
2269 + BITMAP_SIZE (num_objs + 1)));
2270 entry->bytes = bytes;
2272 entry->context_depth = 0;
2274 entry->num_free_objects = 0;
2278 j + HOST_BITS_PER_LONG <= num_objs + 1;
2279 j += HOST_BITS_PER_LONG)
2280 entry->in_use_p[j / HOST_BITS_PER_LONG] = -1;
2281 for (; j < num_objs + 1; j++)
2282 entry->in_use_p[j / HOST_BITS_PER_LONG]
2283 |= 1L << (j % HOST_BITS_PER_LONG);
2285 for (pte = entry->page;
2286 pte < entry->page + entry->bytes;
2288 set_page_table_entry (pte, entry);
2290 if (G.page_tails[i] != NULL)
2291 G.page_tails[i]->next = entry;
2294 G.page_tails[i] = entry;
2296 /* We start off by just adding all the new information to the
2297 end of the varrays, later, we will move the new information
2298 to the front of the varrays, as the PCH page tables are at
2300 push_by_depth (entry, 0);
2303 /* Now, we update the various data structures that speed page table
2305 count_new_page_tables = G.by_depth_in_use - count_old_page_tables;
2307 move_ptes_to_front (count_old_page_tables, count_new_page_tables);
2309 /* Update the statistics. */
2310 G.allocated = G.allocated_last_gc = offs - (char *)addr;