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RAA subsystem: use shift instead of divide

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Make the RAA size always a power of two, so we can use shifts instead
of multiple, expensive divides.
This commit is contained in:
H. Peter Anvin 2008-01-21 16:33:00 -08:00
parent b4daadc0d8
commit c221523976
2 changed files with 23 additions and 23 deletions

28
nasmlib.c

@ -445,7 +445,7 @@ void standard_extension(char *inname, char *outname, char *extension,
#define LEAFSIZ (sizeof(RAA)-sizeof(RAA_UNION)+sizeof(RAA_LEAF))
#define BRANCHSIZ (sizeof(RAA)-sizeof(RAA_UNION)+sizeof(RAA_BRANCH))
#define LAYERSIZ(r) ( (r)->layers==0 ? RAA_BLKSIZE : RAA_LAYERSIZE )
#define LAYERSHIFT(r) ( (r)->layers==0 ? RAA_BLKSHIFT : RAA_LAYERSHIFT )
static struct RAA *real_raa_init(int layers)
{
@ -454,15 +454,13 @@ static struct RAA *real_raa_init(int layers)
if (layers == 0) {
r = nasm_zalloc(LEAFSIZ);
r->stepsize = 1L;
r->shift = 0;
} else {
r = nasm_malloc(BRANCHSIZ);
r->layers = layers;
for (i = 0; i < RAA_LAYERSIZE; i++)
r->u.b.data[i] = NULL;
r->stepsize = RAA_BLKSIZE;
while (--layers)
r->stepsize *= RAA_LAYERSIZE;
r->shift = (RAA_BLKSHIFT-RAA_LAYERSHIFT) + layers*RAA_LAYERSHIFT;
}
return r;
}
@ -485,13 +483,12 @@ void raa_free(struct RAA *r)
int64_t raa_read(struct RAA *r, int32_t posn)
{
if (posn >= r->stepsize * LAYERSIZ(r))
if ((uint32_t)posn >= (UINT32_C(1) << (r->shift + LAYERSHIFT(r))))
return 0; /* Return 0 for undefined entries */
while (r->layers > 0) {
ldiv_t l;
l = ldiv(posn, r->stepsize);
r = r->u.b.data[l.quot];
posn = l.rem;
int32_t l = posn >> r->shift;
posn &= (UINT32_C(1) << r->shift)-1;
r = r->u.b.data[l];
if (!r)
return 0; /* Return 0 for undefined entries */
}
@ -505,7 +502,7 @@ struct RAA *raa_write(struct RAA *r, int32_t posn, int64_t value)
if (posn < 0)
nasm_malloc_error(ERR_PANIC, "negative position in raa_write");
while (r->stepsize * LAYERSIZ(r) <= posn) {
while ((UINT32_C(1) << (r->shift+LAYERSHIFT(r))) <= (uint32_t)posn) {
/*
* Must add a layer.
*/
@ -516,7 +513,7 @@ struct RAA *raa_write(struct RAA *r, int32_t posn, int64_t value)
for (i = 0; i < RAA_LAYERSIZE; i++)
s->u.b.data[i] = NULL;
s->layers = r->layers + 1;
s->stepsize = LAYERSIZ(r) * r->stepsize;
s->shift = LAYERSHIFT(r) + r->shift;
s->u.b.data[0] = r;
r = s;
}
@ -524,14 +521,13 @@ struct RAA *raa_write(struct RAA *r, int32_t posn, int64_t value)
result = r;
while (r->layers > 0) {
ldiv_t l;
struct RAA **s;
l = ldiv(posn, r->stepsize);
s = &r->u.b.data[l.quot];
int32_t l = posn >> r->shift;
posn &= (UINT32_C(1) << r->shift)-1;
s = &r->u.b.data[l];
if (!*s)
*s = real_raa_init(r->layers - 1);
r = *s;
posn = l.rem;
}
r->u.l.data[posn] = value;

18
nasmlib.h

@ -266,13 +266,15 @@ void fwriteint64_t(uint64_t data, FILE * fp);
void fwriteaddr(uint64_t data, int size, FILE * fp);
/*
* Routines to manage a dynamic random access array of int32_ts which
* Routines to manage a dynamic random access array of int64_ts which
* may grow in size to be more than the largest single malloc'able
* chunk.
*/
#define RAA_BLKSIZE 32768 /* this many longs allocated at once */
#define RAA_LAYERSIZE 32768 /* this many _pointers_ allocated */
#define RAA_BLKSHIFT 15 /* 2**this many longs allocated at once */
#define RAA_BLKSIZE (1 << RAA_BLKSHIFT)
#define RAA_LAYERSHIFT 15 /* 2**this many _pointers_ allocated */
#define RAA_LAYERSIZE (1 << RAA_LAYERSHIFT)
typedef struct RAA RAA;
typedef union RAA_UNION RAA_UNION;
@ -288,14 +290,16 @@ struct RAA {
* structures.
*/
int layers;
/*
* Number of real data items spanned by one position in the
* `data' array at this level. This number is 1, trivially, for
* `data' array at this level. This number is 0 trivially, for
* a leaf (level 0): for a level 1 branch it should be
* RAA_BLKSIZE, and for a level 2 branch it's
* RAA_LAYERSIZE*RAA_BLKSIZE.
* RAA_BLKSHIFT, and for a level 2 branch it's
* RAA_LAYERSHIFT+RAA_BLKSHIFT.
*/
int32_t stepsize;
int shift;
union RAA_UNION {
struct RAA_LEAF {
int64_t data[RAA_BLKSIZE];