Bug 248995

Summary:	[WebAssembly SIMD] Emulate 8-bit shift instructions and i8x16.popcnt on Intel
Product:	WebKit	Reporter:	David Degazio <d_degazio>
Component:	WebAssembly	Assignee:	David Degazio <d_degazio>
Status:	RESOLVED FIXED
Severity:	Normal	CC:	webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified
See Also:	https://bugs.webkit.org/show_bug.cgi?id=248639
Bug Depends on:
Bug Blocks:	246345

Description David Degazio 2022-12-08 16:59:10 PST

While most other SIMD bitwise operations are tracked in https://bugs.webkit.org/show_bug.cgi?id=248639, I'm splitting off the following instructions:

 - i8x16.shl, i8x16.shr_s, i8x16.shr_u
 - i8x16.popcnt

into this bug so they don't hold up the other patch. None of these instructions are supported natively on Intel, at least without AVX-512, and they also
aren't easy to emulate. So they require some additional effort to implement necessary supporting instructions and figure out the best isel.

Comment 1 David Degazio 2022-12-08 17:03:14 PST

rdar://103159176

Comment 2 David Degazio 2022-12-12 10:36:08 PST

Looks like despite logical right-shift being supported for 64-bit elements, arithmetic right-shift is only supported with AVX-512 (which we really can't assume will be present). So we also need to emulate i64x2.shr_s.

Comment 3 David Degazio 2022-12-16 13:44:25 PST

Pull request: https://github.com/WebKit/WebKit/pull/7777

Comment 4 EWS 2022-12-19 12:45:57 PST

Committed 258089@main (7d8a35c36444): <https://commits.webkit.org/258089@main>

Reviewed commits have been landed. Closing PR #7777 and removing active labels.