GAS parser

[Ivan Pryanishnikov]

Hi,

I'm going to port binutils to a new target and looking at
the organization of the package.  

I have a question concerning GAS: some ports (eg, bfin) use 
lex/bison extensions (eg, bfin-lex.l, bfin-parse.y) to write their
parsers.

I was wandering about the reasons behind; possibly some of them
are:
 - it's easier (generally) in some sense
 - it's not possible to solve their parsing problems in a standard way
 - they had some non-gnu assembler and just adjust/reuse it for the 
   binutils assembler (because it's easier than to write from scratch)
 - ??

Could you please comment this issue.
Thanks,
Ivan