Re: demand_empty_rest_of_line and ignore_rest_of_line

[Alan Modra <amodra@bigpond.net.au>]

On Mon, Apr 26, 2004 at 05:51:44PM -0700, Zack Weinberg wrote:
> Uh, when I said "collapse the parsing logic together" I meant "think
> of a way to get rid of the machine-dependent parsers to the maximum
> extent possible."  While thinking very carefully about how to make the
> parser go blazingly fast *without* special tricks.  I'm quite
> confident this is possible.  Assembly syntax - with or without extra
> added whitespace - is not complicated, nor does it vary that much
> across architectures supported by GAS.

One thing that complicates do_scrub_chars in gas, for very little gain,
is trying to remove all unneeded whitespace.  For example,

	foo:	mov	%eax, $2 + 3 +   4

is turned into

	foo: mov %eax,$2+3+4

The aim being to render whitespace removal unnecessary in target
dependent code.  That's a good idea until you encounter constructs like:

	foo: addr16 mov %eax,0

where the "opcode" part of the instruction itself has whitespace.
Without various hacks, do_scrub_chars would turn the above into

	foo: addr16 mov%eax,0

Other architectures have similar assembly constructs.  So I think you
underestimate the complexity in a general parser design.  Just
separating an assembly line into label, opcode, operands isn't so easy!

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre