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Re: [wwwdocs] Vectorizer's updates to 4.3.0 changes


Ira Rosen <IRAR@il.ibm.com> writes:

> Andi Kleen <andi@firstfloor.org> wrote on 11/03/2008 13:21:22:
>
>> On Tue, Mar 11, 2008 at 06:50:51AM -0400, Jakub Jelinek wrote:
>> > On Tue, Mar 11, 2008 at 11:41:32AM +0100, Andi Kleen wrote:
>> > You don't need sse2 nor altivec enabled (though of course vectorization
> is
>> > better if you do).  Consider say:
>>
>> I was actually aware of the integer vectorizations, but I expect you'll
>> only get significant benefits from the vectorizer with SSE2 (on x86 at
> least).
>> Ira mentioned this for PPC/Altivec too. So while you're technically
> correct
>> I expect for high level documentation purposes recommending SSE2/Altivec
>> would be still the right thing and most helpful to the users.
>
> Is this better?
>
> Ira
>
> Index: changes.html
> ===================================================================
> RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.3/changes.html,v
> retrieving revision 1.102
> diff -c -p -r1.102 changes.html
> *** changes.html        28 Feb 2008 00:53:41 -0000      1.102
> --- changes.html        12 Mar 2008 07:15:55 -0000
> ***************
> *** 154,159 ****
> --- 154,164 ----
>       <code>-fno-signed-zeros</code>, as it enables reassociation and thus
>       may introduce or remove traps.</li>
>
> +     <li>The <code>-ftree-vectorize</code> option is now on by default
> under
> +     <code>-O3</code>. In order to generate code for a SIMD extension, it
> +     has to be specified as well: use <code>-maltivec</code> for PowerPC
> +     platforms and <code>-msse/-msse2</code> for i?86 and x86_64.

You should not need -msse/-msse2 for x86-64 at all since that is the
default.  If you do not this, I would consider it a bug.

Andreas
-- 
 Andreas Jaeger, Director Platform / openSUSE, aj@suse.de
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