Test b4

PPC b4 (BasicFour)
"Simple sync test, light barrier and isync"
{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         | isync        ;
 stw r6,0,r5    | lwz r2,0,r4  ;


Observed
    1:r1=1; 1:r2=0;