Re: [gentoo-dev] Re: GCC 4.6.0

[Branko Badrljica]

On 03. 04. 2011 16:04, Mike Frysinger wrote:
> On Sun, Apr 3, 2011 at 6:19 AM, Ryan Hill wrote:
>> On Sun, 3 Apr 2011 05:50:32 Duncan wrote:
>>> Ryan Hill posted on Sat, 02 Apr 2011 22:11:12 -0600 as excerpted:
>>>>  You may also want to test your packages with the new -Ofast option to
>>>>  be sure it doesn't have any hardcoded assumptions about -O flags.
>>>
>>> The release description I've read for -Ofast says it includes -fast-math,
>>> among other things, a flag Gentoo has always strongly discouraged (you
>>> break with it, you keep the pieces) and which can get bugs resolved/
>>> invalid as a result.
>>>
>>> Now that gcc 4.6 itself is more strongly supporting it as enabled with one
>>> of the -O options, is that policy going to change, or is Gentoo going to
>>> officially not support -Ofast, as well?
>>
>> I doubt we will.  If a package breaks because of -Ofast there's really
>> nothing we can do about it.  It's not a bug in the compiler or the package,
>> it's that you explicitly told it to generate non-standard-conformant code.
>
> obviously we will look at ICEs and such, but in terms of apps
> misbehaving at runtime, most likely we'll write it up as not a bug
> like Ryan says
> -mike
>
>

Maybe slightly off topic, but still..

1. I've noticed that -Ofast and couple other bits on gcc which I have
seen on Open64 before. Are these new optimisations "imported" from
Open64 or is this simply the result of good old competition of both teams ?


2. Is there any info on gcc version that will support -march=Bulldozer ?
I have googled a couple of gcc-related posts about optimizing for this
CPU architecture intricacies and I have hoped to see support for it in
4.6... Is this stuff still in early development or is it just waiting
for AMD to ship the chips due to some kind of NDA ?