From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20420 invoked by alias); 14 Apr 2002 21:52:24 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 20411 invoked from network); 14 Apr 2002 21:52:23 -0000 Received: from unknown (HELO localhost.redhat.com) (24.112.240.27) by sources.redhat.com with SMTP; 14 Apr 2002 21:52:23 -0000 Received: from cygnus.com (localhost [127.0.0.1]) by localhost.redhat.com (Postfix) with ESMTP id 370C13C3F; Sun, 14 Apr 2002 17:52:30 -0400 (EDT) Message-ID: <3CB9FA1E.6090001@cygnus.com> Date: Sun, 14 Apr 2002 14:52:00 -0000 From: Andrew Cagney User-Agent: Mozilla/5.0 (X11; U; NetBSD macppc; en-US; rv:0.9.9) Gecko/20020328 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Kevin Buettner Cc: gdb-patches@sources.redhat.com Subject: Re: [PATCH] Add support for fpscr for Power / PowerPC targets References: <1020411191706.ZM3109@localhost.localdomain> <3CB5ED4D.8030603@cygnus.com> <1020411203947.ZM3483@localhost.localdomain> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2002-04/txt/msg00508.txt.bz2 > > > For PowerPC, the fpscr regnum is 70, which was an unused slot. For >> > Power, I chose to use the first available slot (71). The other change >> > that this patch makes is to make MQ unavailable for all PowerPC >> > targets except for the 601 processors (which is as it should be). > >> >> Kevin, is there any reason to not just use the same slot for both POWER >> and PowerPC? > > > It would be nice if we could, but I don't see how it can be done without > either > > 1) renumbering some registers for some processors. > or > 2) assigning fpscr to a really high slot that's larger than any > current register. > > I didn't want to do (1) because existing stubs would likely break. > (But see below). > > I didn't want to do (2) because that would introduce a really large > gap between fpscr and the rest of the registers for most processors. > > Slot 70 was an unused slot for PowerPC, but it was used for ``mq'' for > Power. The next available slot for Power was 71, so that's what I used > for Power. > > Also, for PowerPC, slot 70 was already in the set of PPC_UISA_SPRS and > that's exactly where fpscr belongs. > > If we don't mind a minor violation of (1), I could reassign mq to slot 71 > for Power. That would free up slot 70 so that Power would also have > fpscr available at the same slot number as PowerPC. This might be a > relatively safe thing to do since it's likely that there aren't many > (any?) existing stubs for the Power architecture. It'll require some > adjustments to rs6000-nat.c, but I'm willing to make those adjustments. > > Opinions? Thanks for explaining this. I guess just add the above as a comment. Andrew