I misread Janis's latest patch that I approved. The patch was suppose to enable -mabi=altivec when -maltivec is enabled, not change the default ABI.
For other OSes, -mabi=altivec is the default, so -maltivec just works and produces correct code. If a user enables -maltivec on powerpc32-linux explicitly or implicitly (with -mcpu=970 or -mcpu=power6), presumably he or she want GCC to produce correct, self-consistent, ABI-compliant Altivec code. Because no other OSes require an explicit invocation of -mabi=altivec and most users do not expect to need multiple commandline options for correct operation, users are confused. Therefore, the plan is for -maltivec to imply -mabi=altivec for ppc32-linux. In summary, the patch is suppose to make -maltivec produce correct code on ppc32-linux. Mark, I appreciate your and Daniel's suggestions, but that is not what we wish to implement for ppc32-linux. Thanks, David