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Re: gcc 3.4 and altivec code generation?
- From: David Edelsohn <dje at watson dot ibm dot com>
- To: Jack Howarth <howarth at bromo dot med dot uc dot edu>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 12 Nov 2003 12:43:53 -0500
- Subject: Re: gcc 3.4 and altivec code generation?
- References: <200311121708.MAA87969@bromo.msbb.uc.edu>
>>>>> Jack Howarth writes:
Jack> I asked this awhile back but was wondering if
Jack> the situation had changed for gcc 3.4. I am wondering
Jack> if it is possible yet to force the gcc, g++ and g77
Jack> compilers to automatically generate code for math
Jack> operations on the altivec?
GCC does not yet have auto-vectorization support. That is being
developed in conjunction with the Tree-SSA infrastructure.
Jack> Also under
Jack> what circumstances would it make much of an impact
Jack> to switch from the FPU to the Altivec for calculations?
Altivec does not support double precision floating point types.
If you manually vectorize single precision floating point operations and
the data is properly aligned, you should see a performance improvement.
David