933760 - Have TI track a TypeRepresentation for each type descriptor

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Niko Matsakis [:nmatsakis]]

As of bug 898347, we associate a TypeRepresentation with typed object instances, but there is nothing in particular associated with *type descriptors*. Particularly when optimizing new object construction (bug 933277) we need the ability to figure out what type a type descriptor represents.

There are two options:

1. Give each type descriptor a singleton type.

2. Associate a type object with each type representation (canonical form of a type descriptor) and then use that type object for the type descriptor.

The latter seems more efficient (fewer type objects overall) so that's the path I've taken thus far.

Comment 1

[Niko Matsakis [:nmatsakis]]

Attachment: Bug933760.diff

Comment 2

[Brian Hackett [Laid off!]]

Comment on attachment 825987 [details] [diff] [review]
Bug933760.diff

Review of attachment 825987 [details] [diff] [review]:
-----------------------------------------------------------------

Sorry for the delay.

::: js/src/builtin/TypeRepresentation.h
@@ +22,5 @@
> +  this object is never exposed to user code (it is used by self-hosted
> +  code). Type representations are interned into a hashset in the
> +  compartment (typeReprs), meaning that you can compare two type
> +  representations for equality just using `==`. If they are equal,
> +  it means that they represent the same binary layout.

Preexisting, but can you change the format of this comment to match other block comments in js?

Comment 3

[Niko Matsakis [:nmatsakis]]

Attachment: Bug933760.diff

Carrying over r+ from bhackett

Comment 4

[Niko Matsakis [:nmatsakis]]

Try run: https://tbpl.mozilla.org/?tree=Try&rev=f3293d78542c (along with bug 922115)

Comment 5

[Niko Matsakis [:nmatsakis]]

Try run: https://tbpl.mozilla.org/?tree=Try&rev=804a94fb8dab (along with bug 922115)

Comment 6

[Niko Matsakis [:nmatsakis]]

https://tbpl.mozilla.org/?tree=Try&rev=804a94fb8dab

Comment 7

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/c996211971a8