Test RfiSwp

AArch64 RfiSwp
(*
  Test the specific total order case of atomicity,
  where extern write (by P0) is gmo-in-between
  of R and W of an atomic pair (by P1).
  P2 is here to force store-forwarding on P1.
  Swap version.
*)   
{
0:X1=x;
1:X1=x; 1:X5=y;
2:X1=x; 2:X5=y;

}
 P0          | P1                  | P2          ;
 MOV W0,#1   | MOV W0,#2           | MOV W0,#1   ;
 STR W0,[X1] | STR W0,[X1]         | STR W0,[X5] ;
             | MOV W3,#3           | DMB SY      ;
             | SWP W3,W2,[X1]      | LDR W2,[X1] ;
             | AND W9,W2,#128      |             ;
             | LDR W8,[X5,W9,SXTW] |             ;
Observed
    x=3; 2:X2=2; 1:X8=0; 1:X2=2;
and x=1; 2:X2=2; 1:X8=0; 1:X2=2;
and x=3; 2:X2=1; 1:X8=0; 1:X2=2;
and x=1; 2:X2=0; 1:X8=0; 1:X2=2;
and x=3; 2:X2=1; 1:X8=0; 1:X2=1;