589 lines
12 KiB
C
589 lines
12 KiB
C
/* Simple garbage collection for the GNU compiler.
|
||
Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003
|
||
Free Software Foundation, Inc.
|
||
|
||
This file is part of GCC.
|
||
|
||
GCC is free software; you can redistribute it and/or modify it
|
||
under the terms of the GNU General Public License as published by
|
||
the Free Software Foundation; either version 2, or (at your option)
|
||
any later version.
|
||
|
||
GCC is distributed in the hope that it will be useful, but WITHOUT
|
||
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
|
||
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
|
||
License for more details.
|
||
|
||
You should have received a copy of the GNU General Public License
|
||
along with GCC; see the file COPYING. If not, write to the Free
|
||
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
|
||
02111-1307, USA. */
|
||
|
||
#include "config.h"
|
||
#include "system.h"
|
||
#include "coretypes.h"
|
||
#include "tm.h"
|
||
#include "rtl.h"
|
||
#include "tree.h"
|
||
#include "tm_p.h"
|
||
#include "flags.h"
|
||
#include "varray.h"
|
||
#include "ggc.h"
|
||
#include "toplev.h"
|
||
#include "timevar.h"
|
||
#include "params.h"
|
||
|
||
/* Debugging flags. */
|
||
|
||
/* Zap memory before freeing to catch dangling pointers. */
|
||
#undef GGC_POISON
|
||
|
||
/* Collect statistics on how bushy the search tree is. */
|
||
#undef GGC_BALANCE
|
||
|
||
/* Always verify that the to-be-marked memory is collectable. */
|
||
#undef GGC_ALWAYS_VERIFY
|
||
|
||
#ifdef ENABLE_GC_CHECKING
|
||
#define GGC_POISON
|
||
#define GGC_ALWAYS_VERIFY
|
||
#endif
|
||
|
||
#ifndef HOST_BITS_PER_PTR
|
||
#define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
|
||
#endif
|
||
|
||
/* We'd like a balanced tree, but we don't really want to pay for the
|
||
cost of keeping the tree balanced. We'll settle for the next best
|
||
thing -- nearly balanced.
|
||
|
||
In this context, the most natural key is the node pointer itself,
|
||
but due to the way memory managers work, we'd be virtually certain
|
||
to wind up with a completely degenerate straight line. What's needed
|
||
is to make something more variable, and yet predictable, be more
|
||
significant in the comparison.
|
||
|
||
The handiest source of variability is the low bits of the pointer
|
||
value itself. Any sort of bit/byte swap would do, but such machine
|
||
specific operations are not handy, and we don't want to put that much
|
||
effort into it. */
|
||
|
||
#define PTR_KEY(p) ((size_t)p << (HOST_BITS_PER_PTR - 8) \
|
||
| ((size_t)p & 0xff00) << (HOST_BITS_PER_PTR - 24) \
|
||
| (size_t)p >> 16)
|
||
|
||
/* GC'able memory; a node in a binary search tree. */
|
||
|
||
struct ggc_mem
|
||
{
|
||
/* A combination of the standard left/right nodes, indexable by `<'. */
|
||
struct ggc_mem *sub[2];
|
||
|
||
unsigned int mark : 1;
|
||
unsigned int context : 7;
|
||
unsigned int size : 24;
|
||
|
||
/* Make sure the data is reasonably aligned. */
|
||
union {
|
||
HOST_WIDEST_INT i;
|
||
long double d;
|
||
} u;
|
||
};
|
||
|
||
static struct globals
|
||
{
|
||
/* Root of the object tree. */
|
||
struct ggc_mem *root;
|
||
|
||
/* Data bytes currently allocated. */
|
||
size_t allocated;
|
||
|
||
/* Data objects currently allocated. */
|
||
size_t objects;
|
||
|
||
/* Data bytes allocated at time of last GC. */
|
||
size_t allocated_last_gc;
|
||
|
||
/* Current context level. */
|
||
int context;
|
||
} G;
|
||
|
||
/* Local function prototypes. */
|
||
|
||
static void tree_insert (struct ggc_mem *);
|
||
static int tree_lookup (struct ggc_mem *);
|
||
static void clear_marks (struct ggc_mem *);
|
||
static void sweep_objs (struct ggc_mem **);
|
||
static void ggc_pop_context_1 (struct ggc_mem *, int);
|
||
|
||
/* For use from debugger. */
|
||
extern void debug_ggc_tree (struct ggc_mem *, int);
|
||
|
||
#ifdef GGC_BALANCE
|
||
extern void debug_ggc_balance (void);
|
||
#endif
|
||
static void tally_leaves (struct ggc_mem *, int, size_t *, size_t *);
|
||
|
||
struct alloc_zone *rtl_zone = NULL;
|
||
struct alloc_zone *tree_zone = NULL;
|
||
struct alloc_zone *garbage_zone = NULL;
|
||
|
||
/* Insert V into the search tree. */
|
||
|
||
static inline void
|
||
tree_insert (struct ggc_mem *v)
|
||
{
|
||
size_t v_key = PTR_KEY (v);
|
||
struct ggc_mem *p, **pp;
|
||
|
||
for (pp = &G.root, p = *pp; p ; p = *pp)
|
||
{
|
||
size_t p_key = PTR_KEY (p);
|
||
pp = &p->sub[v_key < p_key];
|
||
}
|
||
*pp = v;
|
||
}
|
||
|
||
/* Return true if V is in the tree. */
|
||
|
||
static inline int
|
||
tree_lookup (struct ggc_mem *v)
|
||
{
|
||
size_t v_key = PTR_KEY (v);
|
||
struct ggc_mem *p = G.root;
|
||
|
||
while (p)
|
||
{
|
||
size_t p_key = PTR_KEY (p);
|
||
if (p == v)
|
||
return 1;
|
||
p = p->sub[v_key < p_key];
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
/* Typed allocation function. Does nothing special in this collector. */
|
||
|
||
void *
|
||
ggc_alloc_typed (enum gt_types_enum type ATTRIBUTE_UNUSED, size_t size)
|
||
{
|
||
return ggc_alloc (size);
|
||
}
|
||
|
||
/* Zone allocation function. Does nothing special in this collector. */
|
||
|
||
void *
|
||
ggc_alloc_zone (size_t size, struct alloc_zone *zone ATTRIBUTE_UNUSED)
|
||
{
|
||
return ggc_alloc (size);
|
||
}
|
||
|
||
/* Alloc SIZE bytes of GC'able memory. If ZERO, clear the memory. */
|
||
|
||
void *
|
||
ggc_alloc (size_t size)
|
||
{
|
||
struct ggc_mem *x;
|
||
|
||
x = xmalloc (offsetof (struct ggc_mem, u) + size);
|
||
x->sub[0] = NULL;
|
||
x->sub[1] = NULL;
|
||
x->mark = 0;
|
||
x->context = G.context;
|
||
x->size = size;
|
||
|
||
#ifdef GGC_POISON
|
||
memset (&x->u, 0xaf, size);
|
||
#endif
|
||
|
||
tree_insert (x);
|
||
G.allocated += size;
|
||
G.objects += 1;
|
||
|
||
return &x->u;
|
||
}
|
||
|
||
/* Mark a node. */
|
||
|
||
int
|
||
ggc_set_mark (const void *p)
|
||
{
|
||
struct ggc_mem *x;
|
||
|
||
x = (struct ggc_mem *) ((const char *)p - offsetof (struct ggc_mem, u));
|
||
#ifdef GGC_ALWAYS_VERIFY
|
||
if (! tree_lookup (x))
|
||
abort ();
|
||
#endif
|
||
|
||
if (x->mark)
|
||
return 1;
|
||
|
||
x->mark = 1;
|
||
G.allocated += x->size;
|
||
G.objects += 1;
|
||
|
||
return 0;
|
||
}
|
||
|
||
/* Return 1 if P has been marked, zero otherwise. */
|
||
|
||
int
|
||
ggc_marked_p (const void *p)
|
||
{
|
||
struct ggc_mem *x;
|
||
|
||
x = (struct ggc_mem *) ((const char *)p - offsetof (struct ggc_mem, u));
|
||
#ifdef GGC_ALWAYS_VERIFY
|
||
if (! tree_lookup (x))
|
||
abort ();
|
||
#endif
|
||
|
||
return x->mark;
|
||
}
|
||
|
||
/* Return the size of the gc-able object P. */
|
||
|
||
size_t
|
||
ggc_get_size (const void *p)
|
||
{
|
||
struct ggc_mem *x
|
||
= (struct ggc_mem *) ((const char *)p - offsetof (struct ggc_mem, u));
|
||
return x->size;
|
||
}
|
||
|
||
/* Unmark all objects. */
|
||
|
||
static void
|
||
clear_marks (struct ggc_mem *x)
|
||
{
|
||
x->mark = 0;
|
||
if (x->sub[0])
|
||
clear_marks (x->sub[0]);
|
||
if (x->sub[1])
|
||
clear_marks (x->sub[1]);
|
||
}
|
||
|
||
/* Free all objects in the current context that are not marked. */
|
||
|
||
static void
|
||
sweep_objs (struct ggc_mem **root)
|
||
{
|
||
struct ggc_mem *x = *root;
|
||
if (!x)
|
||
return;
|
||
|
||
sweep_objs (&x->sub[0]);
|
||
sweep_objs (&x->sub[1]);
|
||
|
||
if (! x->mark && x->context >= G.context)
|
||
{
|
||
struct ggc_mem *l, *r;
|
||
|
||
l = x->sub[0];
|
||
r = x->sub[1];
|
||
if (!l)
|
||
*root = r;
|
||
else if (!r)
|
||
*root = l;
|
||
else if (!l->sub[1])
|
||
{
|
||
*root = l;
|
||
l->sub[1] = r;
|
||
}
|
||
else if (!r->sub[0])
|
||
{
|
||
*root = r;
|
||
r->sub[0] = l;
|
||
}
|
||
else
|
||
{
|
||
*root = l;
|
||
do {
|
||
root = &l->sub[1];
|
||
} while ((l = *root) != NULL);
|
||
*root = r;
|
||
}
|
||
|
||
#ifdef GGC_POISON
|
||
memset (&x->u, 0xA5, x->size);
|
||
#endif
|
||
|
||
free (x);
|
||
}
|
||
}
|
||
|
||
/* The top level mark-and-sweep routine. */
|
||
|
||
void
|
||
ggc_collect (void)
|
||
{
|
||
/* Avoid frequent unnecessary work by skipping collection if the
|
||
total allocations haven't expanded much since the last
|
||
collection. */
|
||
size_t allocated_last_gc =
|
||
MAX (G.allocated_last_gc, (size_t)PARAM_VALUE (GGC_MIN_HEAPSIZE) * 1024);
|
||
|
||
size_t min_expand = allocated_last_gc * PARAM_VALUE (GGC_MIN_EXPAND) / 100;
|
||
|
||
if (G.allocated < allocated_last_gc + min_expand)
|
||
return;
|
||
|
||
#ifdef GGC_BALANCE
|
||
debug_ggc_balance ();
|
||
#endif
|
||
|
||
timevar_push (TV_GC);
|
||
if (!quiet_flag)
|
||
fprintf (stderr, " {GC %luk -> ", (unsigned long)G.allocated / 1024);
|
||
|
||
G.allocated = 0;
|
||
G.objects = 0;
|
||
|
||
clear_marks (G.root);
|
||
ggc_mark_roots ();
|
||
sweep_objs (&G.root);
|
||
|
||
G.allocated_last_gc = G.allocated;
|
||
|
||
timevar_pop (TV_GC);
|
||
|
||
if (!quiet_flag)
|
||
fprintf (stderr, "%luk}", (unsigned long) G.allocated / 1024);
|
||
|
||
#ifdef GGC_BALANCE
|
||
debug_ggc_balance ();
|
||
#endif
|
||
}
|
||
|
||
/* Called once to initialize the garbage collector. */
|
||
|
||
void
|
||
init_ggc (void)
|
||
{
|
||
}
|
||
|
||
/* Start a new GGC zone. */
|
||
|
||
struct alloc_zone *
|
||
new_ggc_zone (const char *name ATTRIBUTE_UNUSED)
|
||
{
|
||
return NULL;
|
||
}
|
||
|
||
/* Destroy a GGC zone. */
|
||
void
|
||
destroy_ggc_zone (struct alloc_zone *zone ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
/* Start a new GGC context. Memory allocated in previous contexts
|
||
will not be collected while the new context is active. */
|
||
|
||
void
|
||
ggc_push_context (void)
|
||
{
|
||
G.context++;
|
||
|
||
/* We only allocated 7 bits in the node for the context. This
|
||
should be more than enough. */
|
||
if (G.context >= 128)
|
||
abort ();
|
||
}
|
||
|
||
/* Finish a GC context. Any uncollected memory in the new context
|
||
will be merged with the old context. */
|
||
|
||
void
|
||
ggc_pop_context (void)
|
||
{
|
||
G.context--;
|
||
if (G.root)
|
||
ggc_pop_context_1 (G.root, G.context);
|
||
}
|
||
|
||
static void
|
||
ggc_pop_context_1 (struct ggc_mem *x, int c)
|
||
{
|
||
if (x->context > c)
|
||
x->context = c;
|
||
if (x->sub[0])
|
||
ggc_pop_context_1 (x->sub[0], c);
|
||
if (x->sub[1])
|
||
ggc_pop_context_1 (x->sub[1], c);
|
||
}
|
||
|
||
/* Dump a tree. */
|
||
|
||
void
|
||
debug_ggc_tree (struct ggc_mem *p, int indent)
|
||
{
|
||
int i;
|
||
|
||
if (!p)
|
||
{
|
||
fputs ("(nil)\n", stderr);
|
||
return;
|
||
}
|
||
|
||
if (p->sub[0])
|
||
debug_ggc_tree (p->sub[0], indent + 1);
|
||
|
||
for (i = 0; i < indent; ++i)
|
||
putc (' ', stderr);
|
||
fprintf (stderr, "%lx %p\n", (unsigned long)PTR_KEY (p), (void *) p);
|
||
|
||
if (p->sub[1])
|
||
debug_ggc_tree (p->sub[1], indent + 1);
|
||
}
|
||
|
||
#ifdef GGC_BALANCE
|
||
/* Collect tree balance metrics */
|
||
|
||
#include <math.h>
|
||
|
||
void
|
||
debug_ggc_balance (void)
|
||
{
|
||
size_t nleaf, sumdepth;
|
||
|
||
nleaf = sumdepth = 0;
|
||
tally_leaves (G.root, 0, &nleaf, &sumdepth);
|
||
|
||
fprintf (stderr, " {B %.2f,%.1f,%.1f}",
|
||
/* In a balanced tree, leaf/node should approach 1/2. */
|
||
(float)nleaf / (float)G.objects,
|
||
/* In a balanced tree, average leaf depth should approach lg(n). */
|
||
(float)sumdepth / (float)nleaf,
|
||
log ((double) G.objects) / M_LN2);
|
||
}
|
||
#endif
|
||
|
||
/* Used by debug_ggc_balance, and also by ggc_print_statistics. */
|
||
static void
|
||
tally_leaves (struct ggc_mem *x, int depth, size_t *nleaf, size_t *sumdepth)
|
||
{
|
||
if (! x->sub[0] && !x->sub[1])
|
||
{
|
||
*nleaf += 1;
|
||
*sumdepth += depth;
|
||
}
|
||
else
|
||
{
|
||
if (x->sub[0])
|
||
tally_leaves (x->sub[0], depth + 1, nleaf, sumdepth);
|
||
if (x->sub[1])
|
||
tally_leaves (x->sub[1], depth + 1, nleaf, sumdepth);
|
||
}
|
||
}
|
||
|
||
#define SCALE(x) ((unsigned long) ((x) < 1024*10 \
|
||
? (x) \
|
||
: ((x) < 1024*1024*10 \
|
||
? (x) / 1024 \
|
||
: (x) / (1024*1024))))
|
||
#define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
|
||
|
||
/* Report on GC memory usage. */
|
||
void
|
||
ggc_print_statistics (void)
|
||
{
|
||
struct ggc_statistics stats;
|
||
size_t nleaf = 0, sumdepth = 0;
|
||
|
||
/* Clear the statistics. */
|
||
memset (&stats, 0, sizeof (stats));
|
||
|
||
/* Make sure collection will really occur. */
|
||
G.allocated_last_gc = 0;
|
||
|
||
/* Collect and print the statistics common across collectors. */
|
||
ggc_print_common_statistics (stderr, &stats);
|
||
|
||
/* Report on tree balancing. */
|
||
tally_leaves (G.root, 0, &nleaf, &sumdepth);
|
||
|
||
fprintf (stderr, "\n\
|
||
Total internal data (bytes)\t%ld%c\n\
|
||
Number of leaves in tree\t%lu\n\
|
||
Average leaf depth\t\t%.1f\n",
|
||
SCALE(G.objects * offsetof (struct ggc_mem, u)),
|
||
LABEL(G.objects * offsetof (struct ggc_mem, u)),
|
||
(unsigned long)nleaf, (double)sumdepth / (double)nleaf);
|
||
|
||
/* Report overall memory usage. */
|
||
fprintf (stderr, "\n\
|
||
Total objects allocated\t\t%ld\n\
|
||
Total memory in GC arena\t%ld%c\n",
|
||
(unsigned long)G.objects,
|
||
SCALE(G.allocated), LABEL(G.allocated));
|
||
}
|
||
|
||
struct ggc_pch_data *
|
||
init_ggc_pch (void)
|
||
{
|
||
sorry ("Generating PCH files is not supported when using ggc-simple.c");
|
||
/* It could be supported, but the code is not yet written. */
|
||
return NULL;
|
||
}
|
||
|
||
void
|
||
ggc_pch_count_object (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
void *x ATTRIBUTE_UNUSED,
|
||
size_t size ATTRIBUTE_UNUSED,
|
||
bool is_string ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
size_t
|
||
ggc_pch_total_size (struct ggc_pch_data *d ATTRIBUTE_UNUSED)
|
||
{
|
||
return 0;
|
||
}
|
||
|
||
void
|
||
ggc_pch_this_base (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
void *base ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
|
||
char *
|
||
ggc_pch_alloc_object (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
void *x ATTRIBUTE_UNUSED,
|
||
size_t size ATTRIBUTE_UNUSED,
|
||
bool is_string ATTRIBUTE_UNUSED)
|
||
{
|
||
return NULL;
|
||
}
|
||
|
||
void
|
||
ggc_pch_prepare_write (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
FILE * f ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
void
|
||
ggc_pch_write_object (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
FILE *f ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
|
||
void *newx ATTRIBUTE_UNUSED,
|
||
size_t size ATTRIBUTE_UNUSED,
|
||
bool is_string ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
void
|
||
ggc_pch_finish (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
|
||
FILE *f ATTRIBUTE_UNUSED)
|
||
{
|
||
}
|
||
|
||
void
|
||
ggc_pch_read (FILE *f ATTRIBUTE_UNUSED, void *addr ATTRIBUTE_UNUSED)
|
||
{
|
||
/* This should be impossible, since we won't generate any valid PCH
|
||
files for this configuration. */
|
||
abort ();
|
||
}
|