On Fri, 22 Oct 1999, Dan Nelson wrote:
> In the last episode (Oct 22), Stephen Roome said:
> > The issues I was trying to raise were really about better
> > optimization for Athlons, and later generations of CPU's, as follows
>
> Optimization issues should be brought up on the egcs mailinglists,
> since that is the compiler we use.
I agree, although I'd still be concerned wether extra support needs to be
added, for example to :
/usr/src/sys/i386/i386/support.s
(perhaps some Athlon optimized bzero/bcopy - or is it totally unnecessary ?)
> > 2) Alignment. By default if code is compiled without -m486 we end up
> > with different alignment strategies taken by gcc. Should the 386
> > strategy still be the default ? (i.e. Should 386 still be considered
> > the expected hardware for FreeBSD)
>
> yes. Edit /etc/make.conf and add -march=i586 if you want to compile
> your machine with pentium-specific code.
I've not got an up to date version of gcc available at the moment (will get
-current over the weekend however and see how things change)
> > 3) Use of SIMD instructions, (MMX and 3DNow!). Are these used by
> > anything ?
>
> Don't the MMX instructions stomp on the floating-point regs?
Think so. Although gas can use them.
(Not sure why we have two version of gas in the source tree though ?)
-rw-r--r-- 1 root wheel 43061 Sep 6 1998
/usr/src/contrib/binutils/include/opcode/i386.h
-rw-r--r-- 1 root wheel 34662 Mar 29 1998
/usr/src/gnu/usr.bin/as/opcode/i386.h
One doesn't define the emms instruction and one does (this is, I believe, an
mmx instr), it seems the default version does have this, so I can't figure what
the other version is for.
On the other hand. How about 3DNow! support ? although I've seen some patches
for egcs to give this support on Athlons. (Again, I'll try this over the
weekend with -current when I can install it..) But they don't yet seem to be
in even the egcs cvs tree. (well they weren't on Wednesday)
Steve
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