Re: floating point sse & sse2

[Daniel Berlin <dan at dberlin dot org>]

On Fri, 1 Feb 2002, rkm@usol.com wrote:

> Hello,
> 
>   I am new to this mailing list, sorry if my question has
> already been discussed here.
>   I will soon have Redhat Linux 7.2 installed on a Pentium 4
> machine. I am trying to determine whether I can make use of the
> floating point streaming simd extensions (SSE,SSE2) with GCC
> or the AS assembler. I assume that if this is possible at all, I
> will probably have to write in-line assembly code with the SSE
> instructions, is that right?

Depends.
To make full use, yes.
However, the current CVS version of gcc can produce serial SSE code for 
floating point (IE use SSE instead of x87).

> However I have downloaded the
> latest version of the binutils I could find on ftp sites (version 2.11.2),
> and I looked at the info files for the AS assembler -- the info
> file says that AS currently does not support floating point SIMD
> for intel processors.
It needs to be updated, it does indeed support it.
> While I saw that the AS assembler can access
> the XMM registers, there are other registers required for SSE that
> are not mentioned in the info file (e.g. CR4).

However, they also work fine.
> Is the info file 
> out of date, or is it true that floating point SSE is not yet supported 
> in AS (or GCC) for intel Pentium processors?
The first.
SSE support in AS has been around for a while.

>  If it is not yet supported, 
> is this a project that is in the works for future versions?
>   Even if SSE is supported in GCC or AS, I also have questions
> whether the Linux kernel can support SSE. I have read that
> the kernel must support context switching for floating point SSE
> to work properly. I don't understand the implications of this, but
> Redhat 7.2 uses kernel version 2.4.7-10 -- Would I have to use
> a different version of the kernel to support SSE?

Nope, that version should work fine.
--Dan