723959 - ES6: Tail-call optimization in IonMonkey

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[David Mandelin [:dmandelin]]

TCO is one of the ES6 proposals, and the proposal requires calls in "proper tail position" to get TCO'd.

There is a benchmark here:

  http://jsperf.com/tco#chart=bar

Comment 1

[Bruno George Moraes]

Hi, in here is a discussion about how TCO makes possible to use constant stack space, so is important in the view of memory consumption. 

http://www.mega-nerd.com/erikd/Blog/CodeHacking/fp-tail-js.html

Comment 2

[David Teller [:Yoric] - still alive but not very active]

I have seen often extracts that look like the following:

   foo();
   return;

Do these count as "proper tail position"?

Comment 3

[Sam Tobin-Hochstadt [:samth]]

(In reply to David Rajchenbach Teller [:Yoric] from comment #2)
> I have seen often extracts that look like the following:
> 
>    foo();
>    return;
> 
> Do these count as "proper tail position"?

No, that's not a proper tail position, because it wouldn't be ok to just return whatever `foo()` returns.  That extract must always return `undefined`.

Comment 5

[Marc Nieper-Wißkirchen]

WebKit is apparently the first widely used ES engine that supports proper tail call elimination:

https://www.webkit.org/blog/4054/es6-in-webkit/

Comment 6

[ebrahim]

https://bugs.chromium.org/p/v8/issues/detail?id=4698 Chrome also is done.

Comment 7

[Alexandre Folle de Menezes]

More details on Webkit:
https://webkit.org/blog/6240/ecmascript-6-proper-tail-calls-in-webkit/

Comment 8

[Andrey Bienkowski]

https://bugzilla.mozilla.org/show_bug.cgi?id=1548706