Test safe237

PPC safe237
"SyncdWW Rfe SyncdRW Rfe DpdR Fri Rfe SyncdRW Wse"
Cycle=SyncdWW Rfe SyncdRW Rfe DpdR Fri Rfe SyncdRW Wse
Relax=
Safe=Fri Wse DpdR ACSyncdRW BCSyncdWW BCSyncdRW
{
0:r2=x; 0:r4=y;
1:r2=y; 1:r5=z;
2:r2=z; 2:r4=a;
3:r2=a; 3:r4=x;
}
 P0           | P1            | P2           | P3           ;
 lwz r1,0(r2) | lwz r1,0(r2)  | lwz r1,0(r2) | li r1,2      ;
 sync         | xor r3,r1,r1  | sync         | stw r1,0(r2) ;
 li r3,1      | lwzx r4,r3,r5 | li r3,1      | sync         ;
 stw r3,0(r4) | li r6,1       | stw r3,0(r4) | li r3,1      ;
              | stw r6,0(r5)  |              | stw r3,0(r4) ;
exists
(a=2 /\ 0:r1=1 /\ 1:r1=1 /\ 1:r4=0 /\ 2:r1=1)