From owner-freebsd-hackers Wed Dec 13 15: 9:49 2000 From owner-freebsd-hackers@FreeBSD.ORG Wed Dec 13 15:09:45 2000 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from chopper.Poohsticks.ORG (chopper.poohsticks.org [63.227.60.73]) by hub.freebsd.org (Postfix) with ESMTP id 48E9837B69B for ; Wed, 13 Dec 2000 15:09:41 -0800 (PST) Received: from chopper.Poohsticks.ORG (drew@localhost.poohsticks.org [127.0.0.1]) by chopper.Poohsticks.ORG (8.10.1/8.10.1) with ESMTP id eBDN9eh29153 for ; Wed, 13 Dec 2000 16:09:40 -0700 Message-Id: <200012132309.eBDN9eh29153@chopper.Poohsticks.ORG> To: freebsd-hackers@FreeBSD.ORG Subject: Re: syscall assembly In-reply-to: Your message of "Wed, 13 Dec 2000 16:04:13 MST." <200012132304.QAA42447@harmony.village.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <29149.976748980.1@chopper.Poohsticks.ORG> Date: Wed, 13 Dec 2000 16:09:40 -0700 From: Drew Eckhardt Sender: drew@chopper.Poohsticks.ORG Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <200012132304.QAA42447@harmony.village.org>, imp@village.org writes: >In message Marc Tar >dif 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. Kocking 16 bytes off the stack pointer won't put it any closer to a 16 byte boundary. -- Home Page For those who do, no explanation is necessary. For those who don't, no explanation is possible. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message