mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-23 11:18:54 +00:00
1952e2e1c1
These bits are taken from the FSF anoncvs repo on 1-Feb-2002 08:20 PST.
518 lines
11 KiB
C
518 lines
11 KiB
C
/* Simple garbage collection for the GNU compiler.
|
|
Copyright (C) 1998, 1999, 2000, 2001 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 "rtl.h"
|
|
#include "tree.h"
|
|
#include "tm_p.h"
|
|
#include "flags.h"
|
|
#include "varray.h"
|
|
#include "ggc.h"
|
|
#include "timevar.h"
|
|
|
|
/* Debugging flags. */
|
|
|
|
/* Zap memory before freeing to catch dangling pointers. */
|
|
#define GGC_POISON
|
|
|
|
/* Collect statistics on how bushy the search tree is. */
|
|
#undef GGC_BALANCE
|
|
|
|
/* Perform collection every time ggc_collect is invoked. Otherwise,
|
|
collection is performed only when a significant amount of memory
|
|
has been allocated since the last collection. */
|
|
#undef GGC_ALWAYS_COLLECT
|
|
|
|
/* 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
|
|
#ifdef ENABLE_GC_ALWAYS_COLLECT
|
|
#define GGC_ALWAYS_COLLECT
|
|
#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;
|
|
#ifdef HAVE_LONG_DOUBLE
|
|
long double d;
|
|
#else
|
|
double d;
|
|
#endif
|
|
} 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;
|
|
|
|
/* Skip garbage collection if the current allocation is not at least
|
|
this factor times the allocation at the end of the last collection.
|
|
In other words, total allocation must expand by (this factor minus
|
|
one) before collection is performed. */
|
|
#define GGC_MIN_EXPAND_FOR_GC (1.3)
|
|
|
|
/* Bound `allocated_last_gc' to 4MB, to prevent the memory expansion
|
|
test from triggering too often when the heap is small. */
|
|
#define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
|
|
|
|
/* Local function prototypes. */
|
|
|
|
static void tree_insert PARAMS ((struct ggc_mem *));
|
|
static int tree_lookup PARAMS ((struct ggc_mem *));
|
|
static void clear_marks PARAMS ((struct ggc_mem *));
|
|
static void sweep_objs PARAMS ((struct ggc_mem **));
|
|
static void ggc_pop_context_1 PARAMS ((struct ggc_mem *, int));
|
|
|
|
/* For use from debugger. */
|
|
extern void debug_ggc_tree PARAMS ((struct ggc_mem *, int));
|
|
|
|
#ifdef GGC_BALANCE
|
|
extern void debug_ggc_balance PARAMS ((void));
|
|
#endif
|
|
static void tally_leaves PARAMS ((struct ggc_mem *, int, size_t *, size_t *));
|
|
|
|
/* Insert V into the search tree. */
|
|
|
|
static inline void
|
|
tree_insert (v)
|
|
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 (v)
|
|
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;
|
|
}
|
|
|
|
/* Alloc SIZE bytes of GC'able memory. If ZERO, clear the memory. */
|
|
|
|
void *
|
|
ggc_alloc (size)
|
|
size_t size;
|
|
{
|
|
struct ggc_mem *x;
|
|
|
|
x = (struct ggc_mem *) 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 (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
|
|
|
|
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 (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 (p)
|
|
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 (x)
|
|
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 (root)
|
|
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 ()
|
|
{
|
|
#ifndef GGC_ALWAYS_COLLECT
|
|
if (G.allocated < GGC_MIN_EXPAND_FOR_GC * G.allocated_last_gc)
|
|
return;
|
|
#endif
|
|
|
|
#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;
|
|
if (G.allocated_last_gc < GGC_MIN_LAST_ALLOCATED)
|
|
G.allocated_last_gc = GGC_MIN_LAST_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 ()
|
|
{
|
|
G.allocated_last_gc = GGC_MIN_LAST_ALLOCATED;
|
|
}
|
|
|
|
/* Start a new GGC context. Memory allocated in previous contexts
|
|
will not be collected while the new context is active. */
|
|
|
|
void
|
|
ggc_push_context ()
|
|
{
|
|
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 ()
|
|
{
|
|
G.context--;
|
|
if (G.root)
|
|
ggc_pop_context_1 (G.root, G.context);
|
|
}
|
|
|
|
static void
|
|
ggc_pop_context_1 (x, c)
|
|
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 (p, indent)
|
|
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), 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 ()
|
|
{
|
|
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 (x, depth, nleaf, sumdepth)
|
|
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 ()
|
|
{
|
|
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%d\n\
|
|
Average leaf depth\t\t%.1f\n",
|
|
SCALE(G.objects * offsetof (struct ggc_mem, u)),
|
|
LABEL(G.objects * offsetof (struct ggc_mem, u)),
|
|
nleaf, (double)sumdepth / (double)nleaf);
|
|
|
|
/* Report overall memory usage. */
|
|
fprintf (stderr, "\n\
|
|
Total objects allocated\t\t%d\n\
|
|
Total memory in GC arena\t%ld%c\n",
|
|
G.objects,
|
|
SCALE(G.allocated), LABEL(G.allocated));
|
|
}
|