Date: Wed, 13 Dec 2000 17:12:40 -0500 (EST) From: Marc Tardif <intmktg@CAM.ORG> To: Alfred Perlstein <bright@wintelcom.net> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: syscall assembly Message-ID: <Pine.LNX.4.10.10012131707550.12495-100000@Gloria.CAM.ORG> In-Reply-To: <20001213141023.O16205@fw.wintelcom.net>
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On Wed, 13 Dec 2000, Alfred Perlstein wrote: > * Marc Tardif <intmktg@CAM.ORG> [001213 13:30] wrote: [ snip ] > > subl $8,%esp > > addl $-8,%esp > > pushl $0 > > pushl $.LC0 > > call open > > FreeBSD passes syscall args on the stack, Linux uses registers. > 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? To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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