Add new tail-call WASM features

[pepelsbey]

Description

• Adds two new tail-call versions of the call function: return_call and return_call_indirect.
• Mentions two sources of information on the WASM tail call functions.

Motivation

To support enabled tail calls in Firefox 121.

Related issues and pull requests

• [WASM] Enable Wasm tail calls by default in release #30333
• Add return_call example for WASM interactive-examples#2693 — potential demo for the return_call

[pepelsbey]

@eqrion could you please have a look?

[github-actions]

Preview URLs

• /en-US/docs/WebAssembly/Reference/Control_flow/call

External URLs (2)

URL: /en-US/docs/WebAssembly/Reference/Control_flow/call
Title: call

• https://github.com/WebAssembly/tail-call/blob/main/proposals/tail-call/Overview.md (1 time) (Note! This may be a new URL 👀)
• https://v8.dev/blog/wasm-tail-call (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2023-12-19 09:57:13)

[yurydelendik]

The specification also adds return_call_ref instruction. This instruction added to complement call_ref, and was part of the function references / GC specification as well (which are landed before tail calls). See https://github.com/WebAssembly/function-references/blob/main/proposals/function-references/Overview.md

[pepelsbey]

@yurydelendik the question is the browser support, we don’t document spec-only features, only the ones that are implemented in browsers. Do you know anything about it?

[yurydelendik]

@yurydelendik the question is the browser support, we don’t document spec-only features, only the ones that are implemented in browsers. Do you know anything about it?

Firefox implements function references and GC proposal in version 120, and tail calls proposal in 121. (Chrome implemented them in other order)

[yurydelendik]

See also https://webassembly.org/roadmap/

[pepelsbey]

Firefox implements function references and GC proposal in version 120, and tail calls proposal in 121

Yes! That’s the reason we’re updating the docs. But is it just return_call and return_call_indirect or return_call_ref is also implemented in Chrome and Firefox? I don’t see V8 mentioning it in the blog post.

[yurydelendik]

I don’t see V8 mentioning it in the blog post.

The V8 implemented it with Wasm GC proposal since they released tail calls long ago -- the return_call_ref is part of both proposals (GC and tail calls).

[pepelsbey]

Right, so the return_call_ref instruction is not part of the tail-call proposal, but GC one. Did I get it right? If so, I’ll file another issue to document return_call_ref on the same page.

[yurydelendik]

If so, I’ll file another issue to document return_call_ref on the same page.

That's fine. This detail is not really important since it was discussed internally in the Wasm WG meetings. return_call_ref can be documented with any proposals.

[bsmth]

Thank you!