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Re: mips $12-$15 are named $t4-$t7


On Apr  8, 2003, Thiemo Seufer <ica2_ts at csv dot ica dot uni-stuttgart dot de> wrote:

>> Anyway, we do have a very serious problem now.  GCC does map t0..t3 to
>> $8..$11 regardless of the ABI, and changing this mapping now may break
>> code that declares register variables using the mnemonic name.

> I guess nothing in gcc uses the memnonic names.

Not in GCC, but if you compile with -mabi=n32 something like:

int i;
int main() {
  register int j asm ("t0");
  asm ("ld $12, %1" : "=r" (j) : "m" (i));
  return j;
}

you lose.  Admittedly, this should have used %0 instead of $12, but
one could conceive of more complex scenarios, such as passing
additional arguments to assembly functions by setting register
variables defined using the mnemonic names, that would indeed break.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva at {redhat dot com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva at {lsd dot ic dot unicamp dot br, gnu.org}
Free Software Evangelist                Professional serial bug killer


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