Altivec Linux support in GCC

[David Edelsohn]

>>>>> Aldy Hernandez writes:

>> -maltivec is the ISA selection flag.  -mabi=xxx is the ABI selection
>> flag.  There's an important distinction from the user's point of view
>> about which flags are ISA selection and which change the ABI, because
>> one set is safe and the other isn't.

Aldy> This set of defaults is not sane from a user's perspective, just 
Aldy> judging from the amount of mail I get on this.  As it stands I doubt 
Aldy> more than 10% of users understand this.

>> short names like -maltivec or -mstring; I believe I made a proposal to
>> change that but never got time to implement it.

Aldy> Well I propose to have -maltivec imply -mabi=altivec; it doesn't matter 
Aldy> if it historically it is an ISA selection flag.  I propose it, am 
Aldy> willing to code it, and dispel the average Joe's confusion.  For that 
Aldy> matter, the patch is included below.  If you propose something else and 
Aldy> not implement it, it really doesn't gain us anything.

	This is inconsistent with all other -mXXX options in the PowerPC
port and will confuse users assuming the rest of the options behave this
way.

David