RE: $ta0 .. $ta3 registers in O32 on MIPS

[<Paul_Koning@Dell.com>]

>The register names $ta0 .. $ta3 were added by SGI for N32 / N64 code.
>Because these reference $8 .. $11 just like $t0 .. $t3 in the O32 ABI their 
>availability in O32 as well appears dangerous, if not a bug:
>
>$ cat s.s 
>       addu    $ta0, $ta0
>$ mips-linux-as -o s.o s.s
>$ file s.o
>s.o: ELF 32-bit MSB relocatable, MIPS, MIPS-I version 1 (SYSV), not stripped $
>
>I was expecting an error message and I'm wondering, was this intentional?

I would say so.  I call this a feature.  It makes it easier to write assembly 
code that assembles without change in both O32 and N32/N64.  Consider a 
function that has 4 or fewer arguments, but needs a pile of scratch registers.  
It can use ta0-ta3 as four scratch registers, which is correct in all the ABIs.

        paul