Test bc

PPC bc (BasicTwelve)
"Double sync test, with barriers"
{
 0:r6=1;
 0:r4=x; 0:r5=y;
 1:r4=x; 1:r5=y;
 2:r4=x; 2:r5=y;
}
P0               | P1                | P2 ;
 stw r6,0(r4)    | lwz r1,0(r5)      | lwz r1,0(r5) ;
 lwsync          | xor r7,r1,r1      | xor r7,r1,r1 ;
 stw r6,0(r5)    | lwzx r2,r7,r4     | lwzx r2,r7,r4 ;


exists (1:r1=1 /\ 1:r2=0 \/ 2:r1=1 /\ 2:r2=0)