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Re: [RFA:] Fix for lsb0? in -gen-extract-word, take 2.
- From: "Frank Ch. Eigler" <fche at redhat dot com>
- To: Hans-Peter Nilsson <hp at bitrange dot com>
- Cc: cgen at sources dot redhat dot com
- Date: Mon, 24 Jun 2002 23:47:46 -0400
- Subject: Re: [RFA:] Fix for lsb0? in -gen-extract-word, take 2.
- References: <Pine.BSF.4.30.0206242149010.46015-100000@dair.pair.com>
Hi -
On Mon, Jun 24, 2002 at 09:50:00PM -0400, Hans-Peter Nilsson wrote:
> Here's a less intrusive fix since I couldn't wrap my head around
> what adjustment there should be for the "<<" expression. I
> can't figure out whether it actually has lsb0?-issues at all, so
> I'll not touch it. Again, only tested on the CRIS (wip) target.
> [...]
Let me voice one note of caution regarding this area. cgen is
not fully developed with respect to variable-length instruction
sets, and some other odd cgen-isa parametrizations. This has
been making it necessary to use lsb0=#f for several cpu ports.
I'm worried that modification of something as low-level as
gen-extract-* can easily break these unusual ports.
Unfortunately, only "medium-weird" ports are on the sourceware
cgen repository, so it's possible that a change will break only
a port you don't (yet) have access to.
Anyway, please keep in mind that you're treading on fragile
territory.
- FChE