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Minor ABLOCKS_BUSY cleanups in alloc.c

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* src/alloc.c (ABLOCKS_BUSY): Rename arg to avoid potential clash
with member ‘abase’ in definiens.
(lisp_align_malloc, lisp_align_free): Use bool for boolean.
Avoid compiler warning with fewer casts.
(lisp_align_free): Check busy-field values; this can help the
compiler a bit when optimizing, too.
This commit is contained in:
Paul Eggert 2016-06-20 02:05:39 +02:00
parent dd39c6fbeb
commit 9341142dc8
1 changed files with 25 additions and 20 deletions
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45
src/alloc.c
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@ -1178,16 +1178,18 @@ struct ablock
char payload[BLOCK_BYTES];
struct ablock *next_free;
} x;
/* `abase' is the aligned base of the ablocks. */
/* It is overloaded to hold the virtual `busy' field that counts
the number of used ablock in the parent ablocks.
The first ablock has the `busy' field, the others have the `abase'
field. To tell the difference, we assume that pointers will have
integer values larger than 2 * ABLOCKS_SIZE. The lowest bit of `busy'
is used to tell whether the real base of the parent ablocks is `abase'
(if not, the word before the first ablock holds a pointer to the
real base). */
/* ABASE is the aligned base of the ablocks. It is overloaded to
hold a virtual "busy" field that counts twice the number of used
ablock values in the parent ablocks, plus one if the real base of
the parent ablocks is ABASE (if the "busy" field is even, the
word before the first ablock holds a pointer to the real base).
The first ablock has a "busy" ABASE, and the others have an
ordinary pointer ABASE. To tell the difference, the code assumes
that pointers, when cast to uintptr_t, are at least 2 *
ABLOCKS_SIZE + 1. */
struct ablocks *abase;
/* The padding of all but the last ablock is unused. The padding of
the last ablock in an ablocks is not allocated. */
#if BLOCK_PADDING
@ -1206,18 +1208,18 @@ struct ablocks
#define ABLOCK_ABASE(block) \
(((uintptr_t) (block)->abase) <= (1 + 2 * ABLOCKS_SIZE) \
? (struct ablocks *)(block) \
? (struct ablocks *) (block) \
: (block)->abase)
/* Virtual `busy' field. */
#define ABLOCKS_BUSY(abase) ((abase)->blocks[0].abase)
#define ABLOCKS_BUSY(a_base) ((a_base)->blocks[0].abase)
/* Pointer to the (not necessarily aligned) malloc block. */
#ifdef USE_ALIGNED_ALLOC
#define ABLOCKS_BASE(abase) (abase)
#else
#define ABLOCKS_BASE(abase) \
(1 & (intptr_t) ABLOCKS_BUSY (abase) ? abase : ((void **)abase)[-1])
(1 & (intptr_t) ABLOCKS_BUSY (abase) ? abase : ((void **) (abase))[-1])
#endif
/* The list of free ablock. */
@ -1243,7 +1245,7 @@ lisp_align_malloc (size_t nbytes, enum mem_type type)
if (!free_ablock)
{
int i;
intptr_t aligned; /* int gets warning casting to 64-bit pointer. */
bool aligned;
#ifdef DOUG_LEA_MALLOC
if (!mmap_lisp_allowed_p ())
@ -1299,13 +1301,14 @@ lisp_align_malloc (size_t nbytes, enum mem_type type)
abase->blocks[i].x.next_free = free_ablock;
free_ablock = &abase->blocks[i];
}
ABLOCKS_BUSY (abase) = (struct ablocks *) aligned;
intptr_t ialigned = aligned;
ABLOCKS_BUSY (abase) = (struct ablocks *) ialigned;
eassert (0 == ((uintptr_t) abase) % BLOCK_ALIGN);
eassert ((uintptr_t) abase % BLOCK_ALIGN == 0);
eassert (ABLOCK_ABASE (&abase->blocks[3]) == abase); /* 3 is arbitrary */
eassert (ABLOCK_ABASE (&abase->blocks[0]) == abase);
eassert (ABLOCKS_BASE (abase) == base);
eassert (aligned == (intptr_t) ABLOCKS_BUSY (abase));
eassert ((intptr_t) ABLOCKS_BUSY (abase) == aligned);
}
abase = ABLOCK_ABASE (free_ablock);
@ -1341,12 +1344,14 @@ lisp_align_free (void *block)
ablock->x.next_free = free_ablock;
free_ablock = ablock;
/* Update busy count. */
ABLOCKS_BUSY (abase)
= (struct ablocks *) (-2 + (intptr_t) ABLOCKS_BUSY (abase));
intptr_t busy = (intptr_t) ABLOCKS_BUSY (abase) - 2;
eassume (0 <= busy && busy <= 2 * ABLOCKS_SIZE - 1);
ABLOCKS_BUSY (abase) = (struct ablocks *) busy;
if (2 > (intptr_t) ABLOCKS_BUSY (abase))
if (busy < 2)
{ /* All the blocks are free. */
int i = 0, aligned = (intptr_t) ABLOCKS_BUSY (abase);
int i = 0;
bool aligned = busy;
struct ablock **tem = &free_ablock;
struct ablock *atop = &abase->blocks[aligned ? ABLOCKS_SIZE : ABLOCKS_SIZE - 1];