Test iriwv6

PPC iriwv6 (PPCIriwSix)
"plain irw, one writer"
{
P0:r4=x ; P0:r5=y ;
P1:r4=x ; P1:r5=y ;
P2:r4=x ; P2:r5=y ;
P2:r1=1 ; P2:r2=2 ;
}

P0           |P1           |P2           ;
lwz r1,0(r4) |lwz r2,0(r5) |stw r1,0(r4) ;
lwz r2,0(r5) |lwz r1,0(r4) |stw r2,0(r5) ;
(* Four non seq-consistent behaviors *)
exists
((0:r1=0 /\ 0:r2=0 /\ 1:r1=0 /\ 1:r2=2) \/
 (0:r1=0 /\ 0:r2=2 /\ 1:r1=0 /\ 1:r2=2) \/
 (0:r1=1 /\ 0:r2=0 /\ 1:r1=0 /\ 1:r2=2) \/
 (0:r1=1 /\ 0:r2=2 /\ 1:r1=0 /\ 1:r2=2))