Test iriwv4

PPC iriwv4 (PPCIriwFour)
"iriw, local deps, one writer with local deps"
{
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) ;
xor r3,r1,r1 |xor r3,r2,r2 |lwz r1,0(r4) ;
lwzx r2,r3,r5|lwzx r1,r3,r4|xor r3,r1,r1 ;
             |             |stwx r2,r3,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))