Why is the rex.w prefix not generated for certain instructions in inline assembler blocks?

[Joseph Cassman]

The following artificial code sample fails to compile (DMD 
2.063.2 run on Ubuntu 13.04 on an AMD Athlon II X4 635 processor)

     void main()
     {
         asm
         {
             mov   RAX,0x1ffffffffUL;
             mov   R8,0x1ffffffffUL;
             and   RAX,0xffffffffUL;
             and   R8,0xffffffffUL;
             and   RAX,0x1ffffffffUL;
         }
     }

with this error

     phi/rex.d(9): Error: bad type/size of operands 'and'
     Failed: 'dmd' '-v' '-o-' 'phi/rex.d' '-Iphi'

The error also appears for registers RBX,RCX,RDX,R8 through R15 
and the instructions or,xor,add,sub,cmp.

 From what I understand from the Intel documentation the registers 
R8 through R15 can be accessed by prefixing an instruction with 
an REX.R opcode. And an opcode prefix of REX.W promotes an 
instruction to 64-bits. I was thinking that this opcode was not 
being generated by the compiler. But the disassembly I get (using 
obj2asm, after removing the last statement that will not compile) 
leads me to believe that no particular opcode is provided.

     mov RAX,01FFFFFFFFh
     mov R8,01FFFFFFFFh
     and EAX,0FFFFFFFFh
     and R8,0FFFFFFFFh

So I'm out of ideas on where the error is coming from. Anyone got 
any ideas on what's going on here?

Thanks

Joseph