From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755956AbYCAD44 (ORCPT ); Fri, 29 Feb 2008 22:56:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750878AbYCAD4s (ORCPT ); Fri, 29 Feb 2008 22:56:48 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:62237 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbYCAD4s (ORCPT ); Fri, 29 Feb 2008 22:56:48 -0500 Date: Fri, 29 Feb 2008 22:56:45 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Benjamin Herrenschmidt cc: paulus@samba.org, linuxppc-dev@ozlabs.org, LKML Subject: Re: [PATCH] add strncmp to PowerPC In-Reply-To: <1204340690.15052.457.camel@pasglop> Message-ID: References: <1204301097.14759.6.camel@localhost.localdomain> <1204340690.15052.457.camel@pasglop> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 1 Mar 2008, Benjamin Herrenschmidt wrote: > > Do we have any indication that it performs better than the C one ? See below. > > Ben. > > > > > +_GLOBAL(strncmp) > > + mtctr r5 > > + addi r5,r3,-1 > > + addi r4,r4,-1 > > +1: lbzu r3,1(r5) > > + cmpwi 1,r3,0 > > + lbzu r0,1(r4) > > + subf. r3,r0,r3 > > + beqlr 1 > > + bdnzt eq,1b > > + blr > > + And here's the objdump of the C version: 0000000000000080 <.strncmp>: 80: fb e1 ff f0 std r31,-16(r1) 84: f8 21 ff c1 stdu r1,-64(r1) 88: 7c 69 1b 78 mr r9,r3 8c: 7c a0 2b 79 mr. r0,r5 90: 38 60 00 00 li r3,0 94: 7c 09 03 a6 mtctr r0 98: 7c 3f 0b 78 mr r31,r1 9c: 41 82 00 68 beq- 104 <.strncmp+0x84> a0: 89 69 00 00 lbz r11,0(r9) a4: 88 04 00 00 lbz r0,0(r4) a8: 7c 00 58 50 subf r0,r0,r11 ac: 78 00 06 20 clrldi r0,r0,56 b0: 2f a0 00 00 cmpdi cr7,r0,0 b4: 7c 00 07 74 extsb r0,r0 b8: 7c 03 03 78 mr r3,r0 bc: 40 9e 00 48 bne- cr7,104 <.strncmp+0x84> c0: 2f ab 00 00 cmpdi cr7,r11,0 c4: 41 9e 00 40 beq- cr7,104 <.strncmp+0x84> c8: 38 84 00 01 addi r4,r4,1 cc: 38 69 00 01 addi r3,r9,1 d0: 42 40 00 30 bdz- 100 <.strncmp+0x80> d4: 88 03 00 00 lbz r0,0(r3) d8: 89 24 00 00 lbz r9,0(r4) dc: 38 63 00 01 addi r3,r3,1 e0: 38 84 00 01 addi r4,r4,1 e4: 2f 20 00 00 cmpdi cr6,r0,0 e8: 7c 09 00 50 subf r0,r9,r0 ec: 78 00 06 20 clrldi r0,r0,56 f0: 2f a0 00 00 cmpdi cr7,r0,0 f4: 7c 00 07 74 extsb r0,r0 f8: 40 9e 00 08 bne- cr7,100 <.strncmp+0x80> fc: 40 9a ff d4 bne+ cr6,d0 <.strncmp+0x50> 100: 7c 03 03 78 mr r3,r0 104: e8 21 00 00 ld r1,0(r1) 108: eb e1 ff f0 ld r31,-16(r1) 10c: 4e 80 00 20 blr I'll let you decide ;-) Even if it was logically faster (which I still doubt) it's a hell of a lot of cache lines to waste. -- Steve