From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19868 invoked by alias); 15 Feb 2006 22:10:28 -0000 Received: (qmail 19859 invoked by uid 22791); 15 Feb 2006 22:10:27 -0000 X-Spam-Check-By: sourceware.org Received: from dair.pair.com (HELO dair.pair.com) (209.68.1.49) by sourceware.org (qpsmtpd/0.31) with SMTP; Wed, 15 Feb 2006 22:10:26 +0000 Received: (qmail 1097 invoked by uid 20157); 15 Feb 2006 22:10:24 -0000 Date: Wed, 15 Feb 2006 22:10:00 -0000 From: Hans-Peter Nilsson To: Sylvain Munaut cc: gcc@gcc.gnu.org Subject: Re: Design a microcontroller for gcc In-Reply-To: <43F2666E.70703@246tNt.com> Message-ID: References: <43F2666E.70703@246tNt.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-IsSubscribed: yes Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2006-02/txt/msg00270.txt.bz2 On Wed, 15 Feb 2006, Sylvain Munaut wrote: > * 2 flags Carry & Zero for testing. I think most of your questions have been answered, so let me just add that if nothing else, the port will be much simplified if you make sure that only specific compare instructions set condition codes, i.e. not as a nice side-effect of move, add and sub - or at least make such condition-code side-effects optional. It depends on too many undisclosed details like pipeline restrictions to say whether performance is generally better or worse, but I can tell for sure that the GCC port will be simpler with a specific set of condition-code setting insns. BTW, it depends on the compare (and branch) instructions whether just two flags are sufficient. brgds, H-P