SUMMARY: gcc running across various alpha chip sets

From: Matt Goebel <goebel_at_emunix.emich.edu>
Date: Thu, 16 Mar 2000 11:58:21 -0500 (EST)

Hello,

  I used "configure --host=alpha-dec-osf4.0f".

  I received a lot of suggestions and comments, and decided to build a totaly
generic alpha gcc compiler. It is now installed and appears to work like a
charm.

Many Thanks,
Matt Goebel

I edited the responses down a little to try and keep this summary short.
 
> From: Debra Alpert <alpert_at_fas.harvard.edu>
>
> Matt,
>
> There is a global specs file associated with the gcc distribution. In our
> case, gcc lives under the hierarchy /usr/local/gcc-2.95.2, and the specs
> file has the path:
>
> /usr/local/gcc-2.95.2/lib/gcc-lib/alphaev6-dec-osf4.0f/2.95.2/specs.
>
> Of course, this path will vary depending on your installation, but it's
> found in the appropriate lib subdirectory. In any case, you'll need to
> edit this file on your ev6 system. You'll have to add a line following the
> "*cc1:" directive as below:
>
> *cc1:
> -mcpu=ev56
>
> This will force gcc to use only those instructions that are in the ev56
> subset of the full ev6 set of instructions. By forcing this situation,
> there wiil be no need to emulate instructions when running a program on
> your ev56 systems which was compiled on your ev6 machine.
>
> Hope this helps!
>
> --Deb
>
> Debra Alpert
> Senior Unix Systems Administrator/Programmer
> Faculty of Arts and Sciences, Harvard University

----
> From: Oisin McGuinness <oisin_at_sbcm.com>
> 
> 
> 
> You will need to regenerate and reinstall gcc with the
> configure flag to force it to do generic alpha.
> It is fairly easy to tell what you built it for:
> ls /usr/local/lib/gcc-lib/
> I get alpha-dec-osf4.0d and you probably have something
> like alphaev5-dec-osf4.0d.
> 
> In the gcc build directory, run
> ./configure --build=alpha-dec-osf4.0d
> 
> to configure gcc for the generic alpha support.
> 
> 
-----
> From: Chad Price <cprice_at_molbio.unmc.edu>
> 
> You don't have much choice except to compile it on the system which 
> contains the chip. The EV56 and EV6 have different instruction sets and 
> will do emulation, but they also tell you about it.
> 
> (I have the same combination - an EV56 and an EV6 system...)
> 
-----
> From: Thomas Leitner <tom_at_radar.tu-graz.ac.at>
> 
> This is a problem with gcc. The default configuration always optimizes for
> the CPU it was built on. To turn this off, use the flag -mcpu=ev4 when
> compiling. You could also try to install gcc with -mcpu=ev4 as the
> defaults. This should be explained in the gcc docs.
> 
-----
> 
> From: Olle Eriksson <olle_at_cb.uu.se>
> 
> If you did build it on the EV6 it was built with EV6 specfic
> instructions.
> When you executes the compiler on an ev56, these instructions will be
> emulated, this is the compiler itself not the generated code.The way
> to prevent this is to configure it for an ev56, not for an ev6 processor.
> 
-----
> 
> From: "Frank Wortner" <frank_at_bondnet.com>
> 
> You might want to look at the "-mcpu=" options for GCC.  On the Alpha,  you
> can try specifying -mcpu=ev56 for your client boxes.  I'm guessing that the
> equivalent of a "generic" type would be -mcpu=ev4.   Details are in the
> "Using and Porting the GNU Compiler Collection (GCC)" info file.  It's also
> online at http://www.gnu.org/software/gcc/onlinedocs/gcc_toc.html.  Look
> under "Invoking GCC" and then under "Submodel Options."   You'll see an
> Alphas-specific section there.  It's also online at
> http://www.gnu.org/software/gcc/onlinedocs/gcc_2.html#SEC17.
> 
> Hope this helps.
> 
> Frank
> 
------
> From: "Sean O'Connell" <sean_at_stat.Duke.EDU>
> 
> Did you build gcc on the server?  I bet that it did a -tune host
> on the bootstrap build, and therefore used ev6 goodies.  You might
> consider building gcc from one of the clients (or force the cc
> flag on the intitial build to more pessimistic -> -tune generic).
> 
------
> From: Peter.Stern_at_weizmann.ac.il
> 
> I guess gcc just doesn't know how to take advantage of the
> processor-specific instruction tuning for the Alpha architecture so
> it is by default, generic.  If you want to optimize performance for
> a particular Alpha chip, you need to use a Compaq compiler.
> 
> Regards,
> Peter
> 
------
> From: dsr_at_mail.lns.cornell.edu (Daniel S. Riley)
> 
> I couldn't find a way to tweak this at runtime, so I rebuilt gcc
> with
> 
> configure --host=alpha-dec-osf4.0f
> 
> Which overrides the alphaev6-dec-osf4.0f that config.guess gets.
> If the ev56's are the oldest machine you have,
> 
> configure --host=alphaev56-dec-osf4.0f
> 
> should work for you, and be faster than the completely generic
> alpha-dec-osf4.0f.
----
-- 
Matt J. l. Goebel : goebel_at_emunix.emich.edu : LT staff _at_ EMU : Hail Eris
Neo-Student, Net Lurker, Donut consumer, and procrastinating Furry Fan.
"...When we were living in a dream world, Clouds got in the way
 We gave it up in a moment of madness, And threw it all away..." E.W. & A.P.

Received on Thu Mar 16 2000 - 16:59:16 NZDT