Test isa1v6

PPC isa1v6 (PPCIsaOneSix)
"example 1, ISA p 415"
(* A variation with no barriers *)
{
x=0;y=0;
0:r4=x; 1:r4=x ; 2:r4=x;
        1:r5=y ; 2:r5=y;

0:r1=1 ; 1:r2=2 ;
}
   P0        |  P1           |   P2         ;
stw r1,0(r4) | lwz r1,0(r4)  | lwz r1,0(r5) ;
             | lwsync        | xor r3,r1,r1 ;
             | stw r2,0(r5)  | lwzx r2,r3,r4 ;
locations [1:r1; 2:r1; 2:r2;]
exists (1:r1=1 /\ 2:r1=2 /\ 2:r2=0)