RFC: MIPS paired single vector support

[Nigel Stephens]

cgd@broadcom.com wrote:

>However, even that is debatable.  For instance, say you're on
><some-OS> on a processor that supports .PS.  Does the OS FP Emulator
>support Paired Single?  Maybe it doesn't matter -- maybe you're
>running in a configuration that will never trap to the FPE...  but
>maybe not.
>
>  
>

Good point -  it should probably remain an explicit target option for 
now, and it will needs to be mentioned in the documentation that it may 
require extra OS support that won't be available on all CPUs.

(BTW we're going to need to rethink how ASEs and optional extensions 
like this are encoded in the ELF file header, we're running out of bits 
in the machine-specific flags there).

>MIPS folks: Do you have a CPP predefine that you would like to be
>turned on when -mpaired-single is specified?
>
>  
>

No preference. Jim's suggested __mips_paired_single_float is fine.

>(I didn't actually look into Jim's patch to see if there was one
>there.)
>  
>

Yeah, I think that we missed it too.

Nigel