From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40mtv23pC1zF28B for ; Fri, 18 May 2018 00:27:58 +1000 (AEST) Date: Thu, 17 May 2018 09:27:32 -0500 From: Segher Boessenkool To: Christophe LEROY Cc: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] powerpc/32be: use stmw/lmw for registers save/restore in asm Message-ID: <20180517142732.GU17342@gate.crashing.org> References: <7fbae252f24ec4d30f52f57a549901fa3f799f8f.1523984745.git.christophe.leroy@c-s.fr> <87zi0ymqj6.fsf@concordia.ellerman.id.au> <20180517131550.GR17342@gate.crashing.org> <74ce3f30-6c06-e884-f1ea-1539edbf1a74@c-s.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <74ce3f30-6c06-e884-f1ea-1539edbf1a74@c-s.fr> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, May 17, 2018 at 03:27:37PM +0200, Christophe LEROY wrote: > Le 17/05/2018 à 15:15, Segher Boessenkool a écrit : > >>I guess we've been enabling this for all 32-bit targets for ever so it > >>must be a reasonable option. > > > >On 603, load multiple (and string) are one cycle slower than doing all the > >loads separately, and store is essentially the same as separate stores. > >On 7xx and 7xxx both loads and stores are one cycle slower as multiple > >than as separate insns. > > That's in theory when the instructions are already in the cache. > > But loading several instructions into the cache takes time. Yes, of course, that's why I wrote: > >load/store multiple are nice for saving/storing registers. :-) Segher