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Date: Thu, 25 Jan 2007 20:30:00 -0000
From: Joern Rennecke <joernr@arc.com>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: cgen@sources.redhat.com
Subject: Re: CGEN_DIS_HASH: how to get endianness and/or instruction size?
Message-ID: <20070125203011.GB18395@elsdt-razorfish.arc.com>
References: <20070125142036.GA18395@elsdt-razorfish.arc.com> <20070125145950.GA30933@redhat.com>
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On Thu, Jan 25, 2007 at 09:59:50AM -0500, Frank Ch. Eigler wrote:
> Use the "value" parameter (a host-endian copy of the "base insn")
> rather than the "buffer" parameter.
> 
> > If I want to use the passed instruction value, I need to know what
> > size it is.  [...]
> 
> See m32r_cgen_dis_hash: a hand-written baby insn classifier routine.

I've seen that, but it assumes that if the top 16 its are zero,
the instruction can be hashed as a 16 bit instruction.  That is not
the case for ARCompact.
Branch Conditionally is a 32 bit instuction can have all the top 16 bits
zeroed, and its bottom 16 bits are all operand.

> It is important to realize though that this disassembler hashing
> widget is strictly an optimization.  You can try hard-coding the hash
> value to 0 like some other cgen platforms, and see if the performance
> is bearable.

I can only verify this positively when I've completely finished the
port so that other people can use it...