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Improve performance of variable resolver #668

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65 changes: 61 additions & 4 deletions quickjs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29156,17 +29156,58 @@ static void var_object_test(JSContext *ctx, JSFunctionDef *s,
s->jump_size++;
}

typedef struct VarCacheEntry {
JSAtom var_name;
int scope_level, var_idx;
} VarCacheEntry;

// sweet spot appears to be 12-16 entries
typedef struct VarCache {
uint8_t lru[16]; // indexes into |entries| offset by 1; 0 means free
VarCacheEntry entries[16];
} VarCache;

static BOOL probe_lru_cache(VarCache *c, JSAtom var_name, int scope_level)
{
uint8_t *p, *q, t;
VarCacheEntry *e;
BOOL hit;

hit = TRUE;
for (p = c->lru; p != endof(c->lru); p++) {
if (!*p) {
*p = 1 + (p - c->lru);
goto nohit;
}
e = &c->entries[*p - 1];
if (e->var_name == var_name)
if (e->scope_level == scope_level)
goto hit;
}
p--; // evict oldest entry
nohit:
hit = FALSE;
hit:
t = *p;
q = p;
while (q > c->lru)
*p-- = *--q;
*q = t;
return hit;
}

/* return the position of the next opcode */
static int resolve_scope_var(JSContext *ctx, JSFunctionDef *s,
JSAtom var_name, int scope_level, int op,
DynBuf *bc, uint8_t *bc_buf,
LabelSlot *ls, int pos_next)
LabelSlot *ls, int pos_next, VarCache *cache)
{
int idx, var_idx, is_put;
int label_done;
VarCacheEntry *e;
JSFunctionDef *fd;
JSVarDef *vd;
BOOL is_pseudo_var, is_arg_scope;
BOOL is_pseudo_var, is_arg_scope, cache_hit;

label_done = -1;

Expand All @@ -29177,6 +29218,14 @@ static int resolve_scope_var(JSContext *ctx, JSFunctionDef *s,
var_name == JS_ATOM_new_target ||
var_name == JS_ATOM_this);

cache_hit = probe_lru_cache(cache, var_name, scope_level);
e = &cache->entries[*cache->lru - 1];
if (cache_hit) {
var_idx = e->var_idx;
goto cache_hit; // XXX(bnoordhuis) wrong in presence of with keyword?
}
e->var_name = JS_ATOM_NULL; // invalidate entry

/* resolve local scoped variables */
var_idx = -1;
for (idx = s->scopes[scope_level].first; idx >= 0;) {
Expand Down Expand Up @@ -29222,6 +29271,12 @@ static int resolve_scope_var(JSContext *ctx, JSFunctionDef *s,
}
}
if (var_idx >= 0) {
*e = (VarCacheEntry){
.var_name = var_name,
.scope_level = scope_level,
.var_idx = var_idx,
};
cache_hit:
if ((op == OP_scope_put_var || op == OP_scope_make_ref) &&
!(var_idx & ARGUMENT_VAR_OFFSET) &&
s->vars[var_idx].is_const) {
Expand Down Expand Up @@ -30375,10 +30430,12 @@ static __exception int resolve_variables(JSContext *ctx, JSFunctionDef *s)
int pos, pos_next, bc_len, op, len, i, idx, line_num, col_num;
uint8_t *bc_buf;
JSAtom var_name;
VarCache cache;
DynBuf bc_out;
CodeContext cc;
int scope;

memset(cache.lru, 0, sizeof(cache.lru));
cc.bc_buf = bc_buf = s->byte_code.buf;
cc.bc_len = bc_len = s->byte_code.size;
js_dbuf_init(ctx, &bc_out);
Expand Down Expand Up @@ -30460,7 +30517,7 @@ static __exception int resolve_variables(JSContext *ctx, JSFunctionDef *s)
var_name = get_u32(bc_buf + pos + 1);
scope = get_u16(bc_buf + pos + 5);
pos_next = resolve_scope_var(ctx, s, var_name, scope, op, &bc_out,
NULL, NULL, pos_next);
NULL, NULL, pos_next, &cache);
JS_FreeAtom(ctx, var_name);
break;
case OP_scope_make_ref:
Expand All @@ -30473,7 +30530,7 @@ static __exception int resolve_variables(JSContext *ctx, JSFunctionDef *s)
ls = &s->label_slots[label];
ls->ref_count--; /* always remove label reference */
pos_next = resolve_scope_var(ctx, s, var_name, scope, op, &bc_out,
bc_buf, ls, pos_next);
bc_buf, ls, pos_next, &cache);
JS_FreeAtom(ctx, var_name);
}
break;
Expand Down
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