[gentoo-user] Re: Gcc 4.3.4 ---> 4.4.1

[Nikos Chantziaras <realnc@arcor.de>]

On 08/15/2009 07:48 PM, Mark Knecht wrote:
> On Fri, Aug 14, 2009 at 5:43 PM, Nikos Chantziaras<realnc@arcor.de>  wrote:
>> [...]
>> I am doing an emerge -e system and emerge -e world anyway though since I
>> want to take advantage of the faster code 4.4 produces in general, but also
>> more specific whether or not the new "graphite" optimizer of GCC 4.4 (needs
>> "graphite" USE flag enabled for gcc) will give additional performance gain.
>>
>> (If anyone is interested in that, you need to first add:
>>
>>   -floop-interchange -floop-strip-mine -floop-block
>>
>> to CFLAGS/CXXFLAGS (the options enabling the Graphite optimizer) and then
>> "emerge -e" system and world.)
>
> Are there any Gentoo upgrade instructions for these flags or did you
> figure this out from other sources?

The upgrade instructions don't deal with CFLAGS.  The specific GCC flags 
are from GCC's documentation.  My CFLAGS were "-O2 -march=core2 -pipe" 
previously, and I just added to that the new GCC 4.4 graphite flags.


> If I was going to switch to 4.4
> seems like I'd want to get as much performance as I could safely get.

I'm afraid there's not enough testing on the graphite optimizer yet to 
tell if those flags are as safe as -O2.  In other words, you're on your own.


> I'm assuming that the list above is possibly not the complete list you
> might have in make.conf???

No, the complete list of CFLAGS/CXXFLAGS in my make.conf now is:

-march=core2 -O2 -floop-interchange -floop-strip-mine -floop-block -pipe

And that's it.  I was using very sane CFLAGS and I don't now if those 
three new "-floop" graphite flags count as "ricer CFLAGS" or not, since 
as I said previously, there's not enough testing yet :P