Status: New
Owner: ----
Labels: Type-Bug Priority-Medium
New issue 1212 by [email protected]: Speedup invocation of methods on
primitive string values.
http://code.google.com/p/v8/issues/detail?id=1212
String.prototype.a = function () { };
var N = 1e7;
function foo () {
var a = "a";
String.prototype.a = function () { };
for (var i = 0; i < N; i++) {
a.a();
}
}
function bar () {
var a = "a";
for (var i = 0; i < N; i++) {
new String(a).a();
}
}
function baz () {
var a = new String("a");
for (var i = 0; i < N; i++) {
a.a();
}
}
function m (f) {
var s = Date.now();
f();
print(Date.now() - s);
}
m(foo);
m(bar);
m(baz);
$ ./shell test-string.js
19750
175
89
100x times difference is unexpected.
There two major problems here:
1) we do not have specialized IC for calls that require coercion to object
so we constantly go to the runtime system.
2) something strange happened with GC: V8 is constantly hitting mark-sweep
(while it should be scavenging, and it was before I updated my clean
checkout to the bleeding_edge HEAD).
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