959161 - Use eager allocation for Array(x) inlined in Ion

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

Bug 799122 fixed Array(x) to eagerly allocate for small arrays. This patch updates the Ion-inlined version to do the same.

See bug 626165 comment 6, this wins at least 20% there. The micro-benchmark below improves from 205 ms to 60 ms.

function f() {
    for (var i=0; i<100000; i++) {
	var a = new Array(80);
	for (var j=0; j<a.length; j++) {
	    a[j] = 0;
	}
    }
}
var t = new Date;
f();
print(new Date - t);

Comment 1

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/cc0ba35ea087

Comment 2

[Till Schneidereit [:till]]

fwiw, the micro-benchmark from comment 0 runs in 41ms in JSC and 19ms in v8 on my system (where our shell takes 220ms without the patch that just landed).

Comment 3

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/cc0ba35ea087