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New way to keep hints for table length

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Instead of using 'alimit' for keeping the size of the array and at
the same time being a hint for '#t', a table now keeps these two
values separate. The Table structure has a field 'asize' with the
size of the array, while the length hint is kept in the array itself.
That way, tables with no array part waste no space with that field.
Moreover, the space for the hint may have zero cost for small arrays,
if the array of tags plus the hint still fits in a single word.
This commit is contained in:
Roberto Ierusalimschy
2024-11-29 17:26:20 -03:00
parent 9329eeac3b
commit 002beeebe7
7 changed files with 146 additions and 249 deletions
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8
lgc.c
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@@ -486,7 +486,7 @@ static void traverseweakvalue (global_State *g, Table *h) {
Node *n, *limit = gnodelast(h);
/* if there is array part, assume it may have white values (it is not
worth traversing it now just to check) */
int hasclears = (h->alimit > 0);
int hasclears = (h->asize > 0);
for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
if (isempty(gval(n))) /* entry is empty? */
clearkey(n); /* clear its key */
@@ -508,7 +508,7 @@ static void traverseweakvalue (global_State *g, Table *h) {
** Traverse the array part of a table.
*/
static int traversearray (global_State *g, Table *h) {
unsigned asize = luaH_realasize(h);
unsigned asize = h->asize;
int marked = 0; /* true if some object is marked in this traversal */
unsigned i;
for (i = 0; i < asize; i++) {
@@ -604,7 +604,7 @@ static l_mem traversetable (global_State *g, Table *h) {
}
else /* not weak */
traversestrongtable(g, h);
return 1 + 2*sizenode(h) + h->alimit;
return 1 + 2*sizenode(h) + h->asize;
}
@@ -790,7 +790,7 @@ static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
Table *h = gco2t(l);
Node *n, *limit = gnodelast(h);
unsigned int i;
unsigned int asize = luaH_realasize(h);
unsigned int asize = h->asize;
for (i = 0; i < asize; i++) {
GCObject *o = gcvalarr(h, i);
if (iscleared(g, o)) /* value was collected? */