Re: Fwd: Re: still no accelerated X ($#!$*)

	Hi,

In this particular case, the base address can change (but very very rarely
such as writing to one Aperature or Another on the Rage 128 card) and all of
the writes are made to either the card memory mapped io or the frame buffer
itself.

Then the memory clobber would force the compiler to reload base_addr
between 2 writes to the frame buffer.

Should I not include the : "memory" clobber in this case?  Will it hurt
performance much?

I think that it is not necessary: the best thing with a compiler which
performs alias analysis might be to tell the truth

asm ("stwbrx %1,%2,%3"
     : "=m" (*(volatile unsigned *)(base_addr+regindex))
     : "r" (regdata), "b" (base_addr), "r" (regindex));

Note we don't use %0, and it won't produce any aditional code. You may
want to check what the compiler would have generated as addressing mode
by appending " # %0" at the end of the code string.

I truly wish there were a constraint for indexed addressing modes (anyway
this will be necessary for proper Altivec support).

	Gabriel.


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