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Bug 501230 - TM: fast path for String.toString (r=gal).

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This commit is contained in:
Brendan Eich
2009-07-15 17:36:24 -07:00
parent 139ea671e7
commit 0084508a18
3 changed files with 52 additions and 6 deletions
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42
js/src/jsobj.cpp
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@@ -4733,6 +4733,48 @@ js_DefaultValue(JSContext *cx, JSObject *obj, JSType hint, jsval *vp)
v = save = OBJECT_TO_JSVAL(obj);
switch (hint) {
case JSTYPE_STRING:
/*
* Optimize for String objects with standard toString methods. Support
* new String(...) instances whether mutated to have their own scope or
* not, as well as direct String.prototype references.
*/
if (OBJ_GET_CLASS(cx, obj) == &js_StringClass) {
jsid toStringId = ATOM_TO_JSID(cx->runtime->atomState.toStringAtom);
JS_LOCK_OBJ(cx, obj);
JSScope *scope = OBJ_SCOPE(obj);
JSScopeProperty *sprop = scope->lookup(toStringId);
if (!sprop && scope->object == obj) {
JSObject *proto = LOCKED_OBJ_GET_PROTO(obj);
if (proto && OBJ_GET_CLASS(cx, proto) == &js_StringClass) {
JS_UNLOCK_SCOPE(cx, scope);
JS_LOCK_OBJ(cx, proto);
scope = OBJ_SCOPE(proto);
sprop = scope->lookup(toStringId);
}
}
if (sprop &&
SPROP_HAS_STUB_GETTER(sprop) &&
SPROP_HAS_VALID_SLOT(sprop, scope)) {
jsval fval = LOCKED_OBJ_GET_SLOT(scope->object, sprop->slot);
if (VALUE_IS_FUNCTION(cx, fval)) {
JSObject *funobj = JSVAL_TO_OBJECT(fval);
JSFunction *fun = GET_FUNCTION_PRIVATE(cx, funobj);
if (FUN_FAST_NATIVE(fun) == js_str_toString) {
JS_UNLOCK_SCOPE(cx, scope);
*vp = obj->fslots[JSSLOT_PRIVATE];
return JS_TRUE;
}
}
}
JS_UNLOCK_SCOPE(cx, scope);
}
/*
* Propagate the exception if js_TryMethod finds an appropriate
* method, and calling that method returned failure.