From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko Carstens Subject: Re: [PATCH 1/5] all: s390: move wrapper infrastructure to generic headers Date: Wed, 3 Feb 2016 09:01:59 +0100 Message-ID: <20160203080159.GA3369@osiris> References: <1453741047-5498-1-git-send-email-ynorov@caviumnetworks.com> <1453741047-5498-2-git-send-email-ynorov@caviumnetworks.com> <20160128121618.GB5418@osiris> <20160128163109.GA8529@yury-N73SV> <20160201114251.GB973@yury-N73SV> <20160202073913.GB3990@osiris> <20160202154331.GA3003@yury-N73SV> <20160202160826.GF3990@osiris> <20160202195434.GA3397@osiris> <20160202204156.GA27290@yury-N73SV> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20160202204156.GA27290@yury-N73SV> Sender: linux-arch-owner@vger.kernel.org List-Archive: List-Post: To: Yury Norov Cc: linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, arnd@arndb.de, pinskia@gmail.com, Prasun.Kapoor@caviumnetworks.com, catalin.marinas@arm.com, Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, agraf@suse.de, klimov.linux@gmail.com, broonie@kernel.org, joseph@codesourcery.com, schwidefsky@de.ibm.com, linux-arm-kernel@lists.infradead.org, christoph.muellner@theobroma-systems.com List-ID: On Tue, Feb 02, 2016 at 11:41:56PM +0300, Yury Norov wrote: > On Tue, Feb 02, 2016 at 08:54:34PM +0100, Heiko Carstens wrote: > > So I think I can summarize my point to: if you can enforce correctness, why > > shouldn't you do it if the performance impact is only a single instruction. > > For aarch64 it's 5 instructions. But what's more important (if ever), > another wrapper takes another i-cache line... > : > stp x29, x30, [sp,#-16]! > mov x29, sp > bl d40 > ldp x29, x30, [sp],#16 > ret Why does gcc allocate a stackframe here? Don't you have tail call optimization?