Romcc Ramblings...

Peter Stuge stuge-linuxbios at cdy.org
Fri Dec 5 13:48:01 CET 2003


On Thu, Dec 04, 2003 at 11:22:08PM -0700, Eric W. Biederman wrote:
> > > 
> > > I would think it would hurt since x86 lets you use those little 
> > > sub-registers (puddle arithmetic), so using bigger registers reduces
> > > the number of registers available.
> > 
> > Yes, being able to use this from romcc would severely lower register
> > pressure I assume. Neither romcc nor the code compiled with it takes
> > care of this at the moment though.
> 
> I tried this at one point.  And the problem is that there
> is not a instruction sequence to move to/from the byte registers
> from a normal 32bit register.

Hmm, there's movzx and movsx for moving to 32 bit, but from 32 to 8 is
worse for esi, edi and ebp. 32->16 works fine of course.

I could be missing something though. :)


//Peter



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