630543 - Constant folding assumes `this` is truthy even in strict functions

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

function f() {
    "use strict";
    return !this;
}
assertEq(f.call(null), true);  // FAILS

Comment 1

[Mike Shaver (:shaver emeritus)]

Is that a valuable optimization to have, even when it's correct?

Comment 2

[Brendan Eich [:brendan]]

(In reply to comment #1)
> Is that a valuable optimization to have, even when it's correct?

It was a freebie in the pre-ES5-strict days, see Boolish. Easily fixed.

/be

Comment 3

[Brendan Eich [:brendan]]

http://hg.mozilla.org/tracemonkey/rev/41e2276b9b78

Jason, could you add comment 0's test? I'm sick at home here...

/be

Comment 4

[Jason Orendorff [:jorendorff]]

Nice patch! I'll push the test tonight; I have a few things to push.

Comment 5

[Brendan Eich [:brendan]]

This should ridealong into b12. We could even put it into m-c today for b11.

/be

Comment 6

[Phil Ringnalda (:philor)]

Backed the test out in http://hg.mozilla.org/tracemonkey/rev/819776ea6cce since it wasn't clear to me whether it was this or the other cset in the same push that caused make check to time out during jit-test/tests/basic/bug627609.js, but the tree was completely hosed.

Comment 7

[Phil Ringnalda (:philor)]

And relanded the test in http://hg.mozilla.org/tracemonkey/rev/a1cba95edcf9, since Brendan said to point the orange-stained Finger of Blame at bug 627692 instead.

Comment 8

[Chris Leary [:cdleary] (not checking bugmail)]

cdleary-bot mozilla-central merge info:
http://hg.mozilla.org/mozilla-central/rev/252f0e61e918
http://hg.mozilla.org/mozilla-central/rev/819776ea6cce (backout)
http://hg.mozilla.org/mozilla-central/rev/a1cba95edcf9