Test safe520

PPC safe520
"SyncsWW Rfe SyncdRW Rfe DpsW Rfe SyncdRR Fre"
Cycle=SyncsWW Rfe SyncdRW Rfe DpsW Rfe SyncdRR Fre
Relax=
Safe=Fre DpsW ACSyncdRR BCSyncsWW BCSyncdRW
{
0:r2=y; 0:r4=x;
1:r2=x;
2:r2=x; 2:r4=y;
3:r2=y;
}
 P0           | P1            | P2           | P3           ;
 lwz r1,0(r2) | lwz r1,0(r2)  | lwz r1,0(r2) | li r1,1      ;
 sync         | xor r3,r1,r1  | sync         | stw r1,0(r2) ;
 li r3,1      | li r4,2       | lwz r3,0(r4) | sync         ;
 stw r3,0(r4) | stwx r4,r3,r2 |              | li r3,2      ;
              |               |              | stw r3,0(r2) ;
exists
(x=2 /\ y=2 /\ 0:r1=2 /\ 1:r1=1 /\ 2:r1=2 /\ 2:r3=0)