The speed of the compiler, was: Re: Combine four insns
Andi Kleen
andi@firstfloor.org
Tue Aug 10 20:23:00 GMT 2010
On Tue, Aug 10, 2010 at 01:51:46PM -0600, Tom Tromey wrote:
> >>>>> "Andi" == Andi Kleen <andi@firstfloor.org> writes:
>
> Richard> I'm sure there is a way to open-code this using integer math.
>
> Andi> I don't think so. Take a look at what PCMPESTRI does. There's no easy
> Andi> replacement, even if you use all the Hacker's Delight tricks
> Andi> (it's really a cool instruction, but also very complicated :-)
>
> This is still pending:
>
> http://gcc.gnu.org/ml/gcc-patches/2010-03/msg00526.html
I see. I suspect my version is faster though :-) (if you have a suitable
CPU)
Also I think David got the "buffer near end of page before hole" case wrong
(although I'm not fully sure that really happens in gcc)
>
> I think any sort of hackery in this area is fine, if it speeds up the
> compiler. All that is needed is someone with the time and motivation to
> do the testing.
My version passes testing, except for a few PCH test cases. I actually
ran it in parallel with the original cleanline and it gave the same
results. Any ideas why it could break PCH?
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
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