Test m3d-correct

PPC m3d-correct (PPCMThreeDepCorrect)
"write-to_read causality, boehm adve PLDI'08 (Fig 5.)"
{
P0:r5=x;
P1:r5=x; P1:r6=y;
P2:r5=x; P2:r6=y;
P0:r1=1; P1:r1=1;
} 
      P0    |       P1    |   P2         ;
stw r1,0,r5 | lwz r2,0,r5 | lwz r2,0,r6  ;
            | xor r9,r2,r2| xor r9,r2,r2 ;
            | stwx r1,r9,r6 | lwzx r1,r9,r5  ;

exists (1:r2=1 /\ 2:r2=1 /\ 2:r1=0)
(* According to boehm failure would reveal non-atomicity of writes *)