Test isa2v6

PPC isa2v6 (PPCIsaTwoSix)
"example 2, ISA p 415"
(* Variation sync/ls/ls/ll *)
{
x=0;y=0;
0:r4=x;                   2:r4=x;
0:r5=y; 1:r5=y ;
        1:r6=z ; 3:r6=z;
                 3:r7=t ; 2:r7=t ;
0:r1=1 ; 0:r2=2 ;
1:r3=3 ; 3:r3=4 ;
}
   P0        |  P1           |   P2         |  P3          ;
stw r1,0(r4) | lwz r2,0(r5)  | lwz r3,0(r7) | lwz r2,0(r6) ;
sync         | xor r9,r2,r2  | xor r9,r3,r3 | xor r9,r2,r2 ;
stw r2,0(r5) | stwx r3,r9,r6 | lwzx r1,r9,r4| stwx r3,r9,r7 ;

locations [1:r2; 2:r3; 2:r1; 3:r2; ]
(* Non-SC: 1:r2=2 /\ 3:r2=3 /\ 2:r3=4 /\ 2:r1=0 *)