Test c4

PPC c4 (BasicCFour)
"Simple sync test, store-sync-load|store-lwsync-load"
{
 0:r1=1; 0:r4=x; 0:r5=y;
 1:r1=1; 1:r4=x; 1:r5=y;
}

P0              | P1               ;
 stw r1,0,r4    | stw r1,0,r5      ;
 sync           | lwsync           ;
 lwz r2,0,r5    | lwz r2,0,r4      ;

exists (0:r2=0 /\ 1:r2=0)
(* because lwsync does not order store-load *)