From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/14512 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Szabolcs Nagy Newsgroups: gmane.linux.lib.musl.general Subject: Re: Minor arm __syscall_cp_asm optimisation Date: Tue, 6 Aug 2019 15:07:10 +0200 Message-ID: <20190806130709.GD22009@port70.net> References: Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="255822"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.10.1 (2018-07-13) To: musl@lists.openwall.com Original-X-From: musl-return-14528-gllmg-musl=m.gmane.org@lists.openwall.com Tue Aug 06 15:07:25 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1huzBV-0014Sk-4g for gllmg-musl@m.gmane.org; Tue, 06 Aug 2019 15:07:25 +0200 Original-Received: (qmail 19625 invoked by uid 550); 6 Aug 2019 13:07:22 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 19606 invoked from network); 6 Aug 2019 13:07:22 -0000 Mail-Followup-To: musl@lists.openwall.com Content-Disposition: inline In-Reply-To: Xref: news.gmane.org gmane.linux.lib.musl.general:14512 Archived-At: * Patrick Oppenlander [2019-08-01 16:00:16 +1000]: > Hi all, > > while debugging something unrelated I noticed a minor optimisation we > can make to __syscall_cp_asm for arm. > > Unless I'm missing something the only reason we needed to preserve the > link register was because we were using a branch-link instruction to > branch to __cp_cancel. Replacing this with a branch means we can avoid > the save/restore as the link register is no longer modified. the change makes sense to me.