1084959 - (a) = ...; aborts syntax parsing

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jan de Mooij [:jandem]]

I was just looking into JSBench performance and noticed we abort syntax parsing for (a) = ... (assignment with parentheses around LHS).

The abort happens in checkAndMarkAsAssignmentLhs, because pn is SyntaxParseHandler::NodeGeneric.

This should improve the facebook/chrome and facebook/firefox tests by about 10%.

Simple testcase:

function f() {
    function g() {
	var a;
	(a) = 3;
    }
    return 3;
}
f();

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Patch

Comment 2

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/d6d519cc677b

Comment 3

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/d6d519cc677b