Test isa2v7

PPC isa2v7 (PPCIsaTwoSeven)
"example 2, ISA p 415"
(* Variation lwsync/*/* *)
{
x=0;y=0;
0:r4=x;          2:r4=x;
0:r5=y; 1:r5=y ;
        1:r6=z ; 2:r6=z;
0:r1=1 ; 0:r2=2 ;
1:r3=3 ;
}
   P0        |  P1           |   P2         ;
stw r1,0(r4) | lwz r2,0(r5)  | lwz r3,0(r6) ;
lwsync       |               |              ;
stw r2,0(r5) | stwx r3,r0,r6 | lwzx r1,r0,r4;

locations [1:r2; 2:r3; 2:r1; ]
exists
  (1:r2=2 /\ 2:r3=3 /\ 2:r1=0)