From owner-freebsd-hackers Wed Dec 13 15: 4:17 2000 From owner-freebsd-hackers@FreeBSD.ORG Wed Dec 13 15:04:16 2000 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from rover.village.org (rover.village.org [204.144.255.66]) by hub.freebsd.org (Postfix) with ESMTP id 1012737B404 for ; Wed, 13 Dec 2000 15:04:15 -0800 (PST) Received: from harmony.village.org (harmony.village.org [10.0.0.6]) by rover.village.org (8.11.0/8.11.0) with ESMTP id eBDN4Ds82656; Wed, 13 Dec 2000 16:04:13 -0700 (MST) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (localhost.village.org [127.0.0.1]) by harmony.village.org (8.9.3/8.8.3) with ESMTP id QAA42447; Wed, 13 Dec 2000 16:04:13 -0700 (MST) Message-Id: <200012132304.QAA42447@harmony.village.org> To: Marc Tardif Subject: Re: syscall assembly Cc: Alfred Perlstein , freebsd-hackers@FreeBSD.ORG In-reply-to: Your message of "Wed, 13 Dec 2000 17:12:40 EST." References: Date: Wed, 13 Dec 2000 16:04:13 -0700 From: Warner Losh Sender: imp@harmony.village.org Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message Marc Tardif writes: : So why is %esp displaced by 16 bytes when only 8 bytes : are necessary (4 for $0 and 4 for $.LC0)? And couldn't : the compiler use a single instruction such as : subl $16,%esp or addl $-16,%esp? Are two instructions : used for pipelining purposes, where subl is synchro- : nised with the first pushl and addl with the second : pushl? gcc tries to align stack to 16 byte boundaries as a speed optiminzation. Why it doesn't do this in one instruction is beyond me. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message