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Field 'lastfree' changed (back) to 'Node *'

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Due to allignment, it is already using the space of a pointer, and
a pointer generates slightly simpler code.
This commit is contained in:
Roberto Ierusalimschy
2024-02-07 13:56:39 -03:00
parent 0c9bec0d38
commit 6063c47031
1 changed files with 16 additions and 14 deletions
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30
ltable.c
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@@ -40,24 +40,26 @@
/* /*
** Only tables with hash parts larget than LIMFORLAST has a 'lastfree' ** Only tables with hash parts larger than 2^LIMFORLAST has a 'lastfree'
** field that optimizes finding a free slot. Smaller tables do a ** field that optimizes finding a free slot. That field is stored just
** before the array of nodes, in the same block. Smaller tables do a
** complete search when looking for a free slot. ** complete search when looking for a free slot.
*/ */
#define LLIMFORLAST 2 /* log2 of LIMTFORLAST */ #define LIMFORLAST 2 /* log2 of real limit */
#define LIMFORLAST twoto(LLIMFORLAST)
/* /*
** Union to store an int field ensuring that what follows it in ** The union 'Limbox' stores 'lastfree' and ensures that what follows it
** memory is properly aligned to store a TValue. ** is properly aligned to store a Node.
*/ */
typedef struct { Node *dummy; Node follows_pNode; } Limbox_aux;
typedef union { typedef union {
int lastfree; Node *lastfree;
char padding[offsetof(struct { int i; TValue v; }, v)]; char padding[offsetof(Limbox_aux, follows_pNode)];
} Limbox; } Limbox;
#define haslastfree(t) ((t)->lsizenode > LLIMFORLAST) #define haslastfree(t) ((t)->lsizenode > LIMFORLAST)
#define getlastfree(t) (&((cast(Limbox *, (t)->node) - 1)->lastfree)) #define getlastfree(t) ((cast(Limbox *, (t)->node) - 1)->lastfree)
/* /*
@@ -593,13 +595,13 @@ static void setnodevector (lua_State *L, Table *t, unsigned int size) {
if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE) if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE)
luaG_runerror(L, "table overflow"); luaG_runerror(L, "table overflow");
size = twoto(lsize); size = twoto(lsize);
if (lsize <= LLIMFORLAST) /* no 'lastfree' field? */ if (lsize <= LIMFORLAST) /* no 'lastfree' field? */
t->node = luaM_newvector(L, size, Node); t->node = luaM_newvector(L, size, Node);
else { else {
size_t bsize = size * sizeof(Node) + sizeof(Limbox); size_t bsize = size * sizeof(Node) + sizeof(Limbox);
char *node = luaM_newblock(L, bsize); char *node = luaM_newblock(L, bsize);
t->node = cast(Node *, node + sizeof(Limbox)); t->node = cast(Node *, node + sizeof(Limbox));
*getlastfree(t) = size; /* all positions are free */ getlastfree(t) = gnode(t, size); /* all positions are free */
} }
t->lsizenode = cast_byte(lsize); t->lsizenode = cast_byte(lsize);
setnodummy(t); setnodummy(t);
@@ -776,8 +778,8 @@ void luaH_free (lua_State *L, Table *t) {
static Node *getfreepos (Table *t) { static Node *getfreepos (Table *t) {
if (haslastfree(t)) { /* does it have 'lastfree' information? */ if (haslastfree(t)) { /* does it have 'lastfree' information? */
/* look for a spot before 'lastfree', updating 'lastfree' */ /* look for a spot before 'lastfree', updating 'lastfree' */
while (*getlastfree(t) > 0) { while (getlastfree(t) > t->node) {
Node *free = gnode(t, --(*getlastfree(t))); Node *free = --getlastfree(t);
if (keyisnil(free)) if (keyisnil(free))
return free; return free;
} }