Test dp4

PPC dp4 (PPCDPFour)
"examples of ppo;rf cycles (dp2 + intermediate rf)"
{
0:r5=x; 0:r6=y;
1:r6=y; 1:r7=z;
2:r7=z; 2:r5=x;
0:r8=t0;
1:r8=t1;
2:r8=t2;
x=0; y=0;

}
P0           |    P1       |  P2         ;
lwz r1,0(r5) |lwz r1,0(r6) |lwz r1,0(r7) ;
stw r1,0(r8) |stw r1,0(r8) |stw r1,0(r8) ;
lwz r3,0(r8) |lwz r3,0(r8) |lwz r3,0(r8) ;
cmpwi r3,0   |xor r9,r3,r3 |xor r9,r3,r3 ;
bne L0       |addi r2,r9,1 |li r2,1      ;
li r2,1      |stw r2,0(r7) |stwx r2,r9,r5;
stw r2,0(r6) |             |             ;
L0:          |             |             ;

locations [0:r1; 1:r1; 2:r1;]
~exists
(
(0:r1=1 /\ 1:r1=1)
)