Test MP+rel+swpWZR-dmb.ld

AArch64 MP+rel+swpWZR-dmb.ld
(* Allowed, SWPA ..,WZR,.. by P1 does not have Acquire semantics *)
{
  x=0; y=0; z=0;
  0:X0=x; 1:X0=x;
  0:X1=y; 1:X1=y;
  1:X2=z;
}

  P0            |  P1                 ;
   MOV W9,#1    |   MOV W9,#2         ;
   STR W9,[X0]  |   SWP  W9, WZR,[X1] ;
   STLR W9,[X1] |   DMB LD            ;
                |   LDR W8,[X0]       ;

Observed
    y=2; 1:X8=0;