Test m3d2

PPC m3d2 (PPCMThreeDepTwo)
"write-to_read causality, boehm adve PLDI'08 (Fig 5.)"
{
P0:r5=x;
P1:r5=x; P1:r8=t; P1:r6=y;
P2:r5=x; P2:r6=y;
P0:r1=1; P0:r2=2; P1:r1=1;
P1:r7=z;
P0:r8=t ;
} 
      P0    |       P1     |   P2         ;
stw r1,0,r5 | lwz r2,0,r8  | lwz r2,0,r6  ;
sync        | xor r9,r2,r2 | xor r9,r2,r2 ;
stw r2,0,r8 | stwx r1,r9,r7| lwzx r1,r9,r5  ;
            | lwz r3,0,r7  |              ;
            | stw r3,0,r6  |              ;
exists (1:r2=2 /\ 2:r2=1 /\ 2:r1=0)