Re: [rfc] Target-described register support for MIPS

[Thiemo Seufer <ths at networkno dot de>]

Maciej W. Rozycki wrote:
> On Tue, 12 Jun 2007, Daniel Jacobowitz wrote:
> 
> > >  Hmm, these look wrong -- no "ta" registers have been defined for old 
> > > ABIs.
> > 
> > OK, I'll drop them.  They came from O32_SYMBOLIC_REGISTER_NAMES in
> > gas/config/tc-mips.c.
> 
>  Hmm, it looks like they may have been defined so that some weird 
> handcoded assembly works for both o32 and n32 by using $t0-$t3 and 
> $ta0-$ta3 -- note how the definitions are swapped for the two ABIs.
> 
>  But the names make no sense for o32 -- "ta" stands for 
> "temporary/argument" and these are obviously not argument registers.  I do 
> not recall seeing any code using these names anyway and portable code will 
> probably refer to the registers by numbers as $4-$15 (once you have 
> recorded or discarded the arguments you are free to use all of these 
> registers as temporaries anyway), possibly hiding them under some 
> preprocessor macros.  And GCC does not care.

The "ta" aliases are supposed to help with writing multi-ABI assembler
code, and are occasionally used for that purpose. I don't think they
are useful for disassembling. When gdb knows the ABI it should IMHO
display the "real" names instead of the "ta" aliases.


Thiemo