Re: [gentoo-dev] Replacing cpu-feature USE flags

[Martin Schlemmer]

On Fri, 2006-07-07 at 02:08 +0200, Diego 'Flameeyes' Pettenò wrote:
> On Friday 07 July 2006 01:54, Ciaran McCreesh wrote:
> > | No, we never spent years telling them not to use your so-called
> > | "CFLAGS hacks" that are rather a proper usage of what the compiler
> > | gives you.
> > Wrong. We did.
> Then you were wrong. I could have spent time explaining them when they make
> sense and why they don't in their usecases. If you did, well, then you really
> need to know better what you do because you seem to me pretty confused
> yourself, and I feel pity for you.
>

Yes, we did.  Were we wrong?  Out of a purest point of view ... maybe.
The problem was though that earlier gcc's was very bad at generating
sse/sse2, and sometimes mmx code.

Users being what they are though (ricers should say it all), they
enabled every flag that sounded like it could make their old box two
times faster.  This included -msse, -msse2, etc.  Which quite frankly
produced bad code in many cases.  So we told the users to not add any
-m* flags, and let gcc do its job with the proper -march.

So yeah, I can see that general use flags for cpu features might become
more tedious with the many new modules of processors out there, but to
say handle it by adding -msse, etc to CFLAGS, will surely if not on
gcc4, but then on gcc3 systems just ask for trouble.

And yes, I know you are saying that that is not exactly what you are
proposing, but the users will see it as a clear passport to stick all
those nice sounding flags just right back in, and then it will be too
late to tell them its not proper thing to do when the bugs start
flooding in.

Anyway, I tried to give some history and some what ifs, but as I
admitted many times in the past, I am no great writer.  You had to be
'there' I guess, *shrug*.


-- 
Martin Schlemmer