Bug 189326

Summary:

[WHLSL] The interpreter should evaluate arguments right-to-left

Product:

WebKit

Reporter:

Thomas Denney <tdenney>

Component:

WebGPU

Assignee:

Thomas Denney <tdenney>

Status:

RESOLVED DUPLICATE

Severity:

Normal

CC:

achristensen, dino, jonlee, mmaxfield, tdenney, webkit-bug-importer

Priority:

Keywords:

InRadar

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

Bug Depends on:

189360

Bug Blocks:

176199, 188402, 189202

Attachments:

Description	Flags
Patch	none
Patch	none
WIP	none

Description Thomas Denney 2018-09-05 16:17:52 PDT

In order to be consistent with C, the arguments of function calls should be evaluated right-to-left. C doesn’t define an evaluation order for operators (like +) but because we treat them as “native functions” we should strictly evaluate them right-to-left.

Comment 1 Thomas Denney 2018-09-05 16:21:52 PDT

Created attachment 348978 [details]
Patch

Comment 2 Thomas Denney 2018-09-05 17:12:43 PDT

Created attachment 348982 [details]
Patch

Comment 3 Alex Christensen 2018-09-05 18:20:20 PDT

Comment on attachment 348982 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=348982&action=review

This order is not determined in C or C++, but it is commonly evaluated in a consistent order for reasons.  See https://en.cppreference.com/w/c/language/eval_order
I think it would be great if WHLSL had a defined order, but don't claim it's to be consistent with C.

> Tools/ChangeLog:8
> +        The behavior of the interpreter now matches the behavior of the compiler

What compiler are you talking about?  It's possible the behavior of that compiler is unspecified but it happens to be right-to-left in all the cases you've checked.

Comment 4 Myles C. Maxfield 2018-09-05 19:12:39 PDT

Comment on attachment 348982 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=348982&action=review

> Tools/WebGPUShadingLanguageRI/Test.js:7637
> +        int foo() { return *bar(10) + *bar(20); }
> +
> +        thread int* bar(int value)
> +        {
> +            int x = value;
> +            return &x;
> +        }

I don't think we should commit a test that is fundamentally wrong.

Comment 5 Thomas Denney 2018-09-05 19:26:10 PDT

(In reply to Alex Christensen from comment #3)
> Comment on attachment 348982 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=348982&action=review
> 
> This order is not determined in C or C++, but it is commonly evaluated in a
> consistent order for reasons.  See
> https://en.cppreference.com/w/c/language/eval_order
> I think it would be great if WHLSL had a defined order, but don't claim it's
> to be consistent with C.
> 
> > Tools/ChangeLog:8
> > +        The behavior of the interpreter now matches the behavior of the compiler
> 
> What compiler are you talking about?  It's possible the behavior of that
> compiler is unspecified but it happens to be right-to-left in all the cases
> you've checked.

The WHLSL -> Metal code generation generates code so that the arguments are explicitly evaluated right-to-left before the function call and are then passed separately.

Comment 6 Thomas Denney 2018-09-06 11:24:10 PDT

Created attachment 349046 [details]
WIP

Comment 7 Thomas Denney 2018-09-10 16:22:43 PDT

The most recent patch of https://bugs.webkit.org/show_bug.cgi?id=188641 resolves this, and it would only be a two line change to that patch to resolve this bug.

*** This bug has been marked as a duplicate of bug 188641 ***

Comment 8 Radar WebKit Bug Importer 2018-09-12 18:41:25 PDT

<rdar://problem/44402790>

Comment 9 Myles C. Maxfield 2018-10-13 14:35:40 PDT

Migrated to https://github.com/gpuweb/WHLSL/issues/42