Test d4

PPC d4 (BasicDFour)
"Simple sync test, load-store deps, causal dep"
{
 0:r4=x; 0:r5=y;
 1:r4=x; 1:r5=y;
}

P0              | P1               ;
 lwz r1,0,r5    | lwz r1,0,r4      ;
 addi r1,r1,1   | addi r1,r1,2     ;
 stw r1,0,r4    | stw r1,0,r5      ;


exists (x=0 /\ y=0)