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Re: rearrange -mcpu= code for rs6000
- From: David Edelsohn <dje at watson dot ibm dot com>
- To: Geoffrey Keating <geoffk at apple dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 25 Sep 2003 00:53:27 -0400
- Subject: Re: rearrange -mcpu= code for rs6000
>>>>> Geoffrey Keating writes:
Geoff> I'll wait a bit before committing this, in the hope that someone can
Geoff> help me with the FIXME. In particular:
Geoff> - Does POWER3 have the GPOPT extensions?
Geoff> - What about POWER4? 620? 630?
Geoff> - Does the 8540 have Altivec?
Just because a processor supports GPOPT extensions, does not mean
that it is a performance benefit for the compiler to generate those
instructions.
Motorola does not mention Altivec support for the 8540 processor
in their documentation.
Also, processors with Altivec extensions are not always used in
settings with Altivec support enabled. MASK_ALTIVEC changes the behavior
of the GCC, especially on targets other than Darwin. I am concerned about
enabling MASK_ALTIVEC based solely on a processor choice.
David