[ruby-core:96761] [Ruby master Misc#16487] Potential for SIMD usage in ruby-core

[email protected] Fri, 10 Jan 2020 12:20:43 +0000 (UTC)
Newsgroups gmane.comp.lang.ruby.core
Message-ID <redmine.journal-83754.20200110122042.3b69fc6dff5617af@ruby-lang.org>
Issue #16487 has been updated by byroot (Jean Boussier).


> for maximum portability, you should use -march=3Dx86-64

Oh I see what you mean now.

Apparently the solution for this is to use `__target__` attributes  https:/=
/gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-target-fu=
nction-attribute



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Misc #16487: Potential for SIMD usage in ruby-core
https://bugs.ruby-lang.org/issues/16487#change-83754

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Assignee: =

----------------------------------------
### Context

There are several ruby core methods that could be optimized with the use of=
 SIMD instructions.

I experimented a bit on `coderange_scan` https://github.com/Shopify/ruby/pu=
ll/2, and Pavel Rosick=FD experimented on `String#strip` https://github.com=
/ruby/ruby/pull/2815.

### Problem

The downside of SIMD instructions is that they are not universally availabl=
e.
So it means maintaining several versions of the same code, and switching th=
em either statically or dynamically.

And since most Ruby users use precompiled binaries from repositories and su=
ch, it would need to be dynamic if we want most users to benefit from it.

So it's not exactly "free speed", as it means a complexified codebase.

### Question

So the question is to know wether ruby-core is open to patches using SIMD i=
nstructions ? And if so under which conditions.

cc @shyouhei





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