make.conf optimzations [was ports vs source]

[stheg olloydson]

it was said by Vulpes Velox:

>The ability to squeze the absolute max out using /etc/make.conf is
>what I love about ports.
>
>CPUTYPE?=athlon-xp
>CFLAGS= -O -m3dnow -msse -mmmx  -pipe
>CXXFLAGS+= -fmemoize-lookups -fsave-memoized -m3dnow -msse -mmmx

Hello,

This post raises a couple of questions I have concerning optimzation. I
just setup 5.2.1p9 on an athlon-xp box. I, too, used the "memoize"
options but I got this when doing a make buildworld:

>cc1plus: error: unrecognized command line option "-fmemoize-lookups"
>cc1plus: error: unrecognized command line option "-fsave-memoized"
>*** Error code 1

I checked the gcc 3.3.3 manual for info (because they worked under
3.2.2) and couldn't find any mention of them. Googling took me to
numerous sites that had the same gcc manpage (unknown version) that
said:

>-fmemoize-lookups 
>-fsave-memoized 
>Use heuristics to compile faster. These heuristics are not enabled by
>default, since they are only effective for certain input files. Other
>input files compile more slowly.

The gcc-1750 support site goes even further and adds:

>The code that implements these flags has rotted; you should probably
>avoid using them.

OK, that's fine. Does that mean, in the versions of gcc in 5.x, these
options are deprecated?

Also, concerning the -mmmx, -m3dnow, and -msse, I read somewhere
(bsdforum.org?) that cputype?=athlon-xp implies those three options,
but I couldn't find a mention of it in the gcc 3.3.3 manual (doesn't
mean it's not there). Is this true, or should they be explicit as in Mr
Velox's post?
Finally, what optimzations are people using on their production 5.2.1
boxen? -mfpmath=sse looks interesting, but is it safe? The manual says:


>The resulting code should be considerably faster in the majority of
>cases and avoid the numerical instability problems of 387 code, but
>may break some existing code that expects temporaries to be 80bit. 
>This is the default choice for the x86-64 compiler. 

Regards,

Stheg


		
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