fs register syntax bug?

[Quentin Neill]

I have some old test code using the FS segment register that used to
assemble but now doesn't:

=== Code:
.intel_syntax noprefix
    mov rdi, qword [fs:rsp + rbp + 0x040000000]

=== Output:
GNU assembler version 2.20.51 (x86_64-unknown-linux-gnu) using BFD
version (GNU Binutils) 2.20.51.20100216
../src/gas/as-new -al fstst.s -o fstst.o
fstst.s: Assembler messages:
fstst.s:2: Error: invalid use of register


I went back a ways and found out that at one point it worked, for
example from December 2008:

=== Output:
GNU assembler version 2.19.51 (x86_64-toolchain-linux-gnu) using BFD
version (GNU Binutils) 2.19.51.20081203
/tools/toolchain.13.64/bin/as -al fstst.s -o fstst.o
GAS LISTING fstst.s                     page 1

   1                    .intel_syntax noprefix
   2 0000 64488BBC          mov rdi, qword [fs:rsp + rbp + 0x040000000]
   2      2C000000
   2      00
   3

I thought I'd post and see if anyone knew why this would happen before
I considered writing up a bug.
-- 
Quentin