[ On Thursday, September 30, 2004 at 19:46:36 (+0200), Holger Weiss wrote: ]
> Subject: Re: What are you using port-sparc for?
>
> That's what I was referring to. "-mcpu=" sets both the instruction set
> and the scheduling parameters, "-mtune=" only sets the latter.

Yes but "-mcpu=" only sets "-mtune=" to the _default_ for the specified
CPU architecture (at least when "-mcpu=" is set to ``an architecture and
not an implementation'').  As far as I'm concerned it only ever really
makes sense to choose an architecture type for "-mcpu=" and an
implementation type for "-mtune=", but GNU option syntax being what it
is, esp. in GCC, all the choices are far too confusing for no good
reason whatsoever -- what a waste of code, no wonder GCC is bloated!)

> My point was that from reading the docs, I would have thought that
> adding "-mtune=supersparc" to "-mcpu=supersparc" wouldn't make _any_
> difference in the resulting code, but maybe I'm missing something?

We're definitely starting to pick nits but what I said was "-mcpu=v8"
(which is the value that makes most sense for this option on this class
of machines :-)

Although I'm not 100% sure (I've not looked at the code), I believe the
default for "-mcpu=v8" is indeed "-mtune=supersparc".

The point though was that it could also be set '-mtune=hypersparc' if
appropriate.  :-)

In any case it would be easy enough to test once one found some
canonical code that would trigger different instruction scheduling on
different implementations.

-- 
						Greg A. Woods
						Planix, Inc.

<woods@planix.com>     +1 416 489-5852 x122     http://www.planix.com/