Test b7

PPC b7 (BasicSeven)
"Simple sync test, effect of reg duplicates"
{0:r6=1; 0:r4=x; 0:r5=y; 1:r4=x; 1:r5=y; x=0; y=0; }

P0               | P1                ;
 stw r6,0(r4)    | lwz r1,0(r5)      ;
 lwsync          | mr r2,r1          ;
 stw r6,0(r5)    | lwz r1,0(r4)      ;


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