From: fche@redhat.com (Frank Ch. Eigler)
To: cgen@sources.redhat.com
Subject: Re: escaping in syntax strings
Date: Mon, 26 Mar 2001 08:49:00 -0000 [thread overview]
Message-ID: <o5snk01nnf.fsf@toenail.toronto.redhat.com> (raw)
In-Reply-To: <o5wv9c1ojl.fsf.cygnus.local.cgen@toenail.toronto.redhat.com>
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
next prev parent reply other threads:[~2001-03-26 8:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-03-25 20:16 Ben Elliston
2001-03-26 5:10 ` Frank Ch. Eigler
2001-03-26 5:22 ` Ben Elliston
[not found] ` <15039.17056.78350.71117.cygnus.local.cgen@scooby.apac.redhat.com>
2001-03-26 8:30 ` Frank Ch. Eigler
[not found] ` <o5wv9c1ojl.fsf.cygnus.local.cgen@toenail.toronto.redhat.com>
2001-03-26 8:49 ` Frank Ch. Eigler [this message]
2001-03-26 9:11 ` Dave Brolley
2001-03-26 14:08 ` Ben Elliston
2001-03-26 14:15 ` Dave Brolley
2001-03-26 14:21 ` Frank Ch. Eigler
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