On Tue, Jul 07, 2009 at 02:40:02PM +0200, Andreas Schwab wrote: > Gabriel Paubert <paubert@xxxxxxx> writes: > > > On Fri, Jul 03, 2009 at 10:57:12PM +0200, Andreas Schwab wrote: > >> The 'Z' constraint is required for a memory operand for insns that don't > >> have an update form (which would be selected by the %U modifier). > > > > Hmmm, I believed that it was for instructions that only have an indexed > > form (all Altivec, byte reverse, and l?arx/st?cx for atomic operations). > > > > Of course none of these instructions have an update form, but they don't > > have an offset encoded in the instruction either. > > Yes, you are right. IIRC there are either all u/x/ux forms or only the > x form. AFAIR IBM (probably) managed to screw up by making an exception for lwa: lwa, lwax and lwaux exist, but not lwau! Gabriel
