From owner-freebsd-current Tue Nov 30 9:36: 8 1999 Delivered-To: freebsd-current@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 3D89614F1A for ; Tue, 30 Nov 1999 09:35:54 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id JAA25885; Tue, 30 Nov 1999 09:35:34 -0800 (PST) (envelope-from dillon) Date: Tue, 30 Nov 1999 09:35:34 -0800 (PST) From: Matthew Dillon Message-Id: <199911301735.JAA25885@apollo.backplane.com> To: Ville-Pertti Keinonen Cc: marcel@scc.nl, current@FreeBSD.ORG Subject: Re: kernel: -mpreferred-stack-boundary=2 ?? References: <19991130133337.25847.qmail@ns.demophon.com> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> > Anyhow, I'll repeat it here - stack alignment does *not* break :> > link-compatibility. It does not change calling conventions, it just :> > adds padding after the args to ensure that local variables can be :> > predictably aligned. : :> So, how does aligning stackframes affect the inherently static property :> of code size then? : :Instructions are inserted to perform that alignment (add padding). :When the alignment is 2 (i.e. on 4-byte boundaries), no padding is :required in typical cases. I can't think of a single case where the stack isn't inherently 4-byte aligned already, whether you use the option or not. To whomever added the option: Did you actually test to see that this option resulted in an improvement? If not, I recommend removing it. It sounds like unnecessary extra junk to me. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message