Re: escaping in syntax strings

[Dave Brolley <brolley at redhat dot com>]

Yes -- see the fr30 for an example of this:

h-r13 -- hardware element
R13 -- special operand
r13base-ld -- pmacro for generating insns which have r13 hardwired but 
still specified

Dave

Frank Ch. Eigler wrote:

> I wrote:
> 
> : [...]
> : By the way, why do you need a "$" in the syntax string?  Are you
> : confusing register name keywords or hexadecimal constants with
> : the markers that actually belong into the syntax strings?
> 
> I just found what Ben was talking about.  It seems that some
> instructions in the assembly language for his target includes dummy
> operands that make explicit the implicit (not-encoded) operands.  For
> example, given a register keyword set such as "$0 .. $7", there are
> some instructions which are hard-wired to use only $0 as an input or
> output, in addition to other inputs/outputs.  Rather than leave the $0
> implicit, this assembly language expects the programmer to specify it.
> Say,
>         compare $0,$2,$3
> instead of
>         compare $2,$3
> 
> So, Ben is trying to implement this in the assembler by including the
> literal string "$0" in the syntax bytes of the instruction.  This is
> not too bad, though a possibly better way would be to associate a
> synthetic cgen operand with that slot, and to give it a parser that
> accepts only "$0", and emits a helpful error message for anything
> else.
> 
> - FChE
> 
>