From: Ronald Hecht <ronald.hecht@uni-rostock.de>
To: cgen@sourceware.org
Subject: Re: Simulator: base_insn and insn in decode.c
Date: Mon, 07 Aug 2006 14:39:00 -0000 [thread overview]
Message-ID: <44D75159.8070804@uni-rostock.de> (raw)
In-Reply-To: <44D273E8.4040006@redhat.com>
Dave Brolley wrote:
> I forgot to address your other question which was about the difficulty
> of setting entire_insn before decoding. It's a bit of a chicken and
> egg situation isnt'y it? You can't set entire insn properly until you
> know something about the insn, but you can't call decode without
> setting entire_insn properly.
I agree, that's always the case.
>
> Your method of calling decode twice won't work because of this.
>
> Most existing ports determine the insn length by looking at a few bits
> in base_insn and use this information to fill entire_insn.
>
> I'm wondering if the decoder shouldn't be redesigned so that all it
> takes is base_insn, which should be all that is necessary to identify
> the insn. The extractors for each format would then read any
> additional bytes as needed. There is already support for this for ISAs
> with insns which are longer than an insn word.
That sounds good. Actually, I'm wondering a bit why the disassembler in
src/opcodes works so great and the simulator port only under certain
circumstances. Anyway. CGEN is great stuff. It helps a lot. Whould you
say that SID is a better choice? Does it work with gdb as SIM does?
Ronald
next prev parent reply other threads:[~2006-08-07 14:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-31 11:58 Ronald Hecht
2006-08-03 21:55 ` Dave Brolley
2006-08-03 22:08 ` Dave Brolley
2006-08-07 14:39 ` Ronald Hecht [this message]
2006-08-07 14:53 ` Ronald Hecht
2006-08-14 21:19 ` Dave Brolley
2006-08-15 8:39 ` Ronald Hecht
2006-08-04 8:51 ` Ronald Hecht
2006-08-14 20:34 ` Dave Brolley
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