Re: nasm over gas?

From: Pavel Machek <pavel@suse.cz>
To: insecure <insecure@mail.od.ua>
Cc: "Michael Frank" <mhf@linuxmail.org>,
	"Yann Droneaud" <yann.droneaud@mbda.fr>,
	"fruhwirth clemens" <clemens-dated-1063536166.2852@endorphin.org>,
	linux-kernel@vger.kernel.org,
	"Jörn Engel" <joern@wohnheim.fh-wedel.de>
Subject: Re: nasm over gas?
Date: Tue, 9 Sep 2003 22:56:27 +0200	[thread overview]
Message-ID: <20030909205626.GJ3944@openzaurus.ucw.cz> (raw)
In-Reply-To: <200309052028.37367.insecure@mail.od.ua>

Hi!

> A random example form one small unrelated program (gcc 3.2):
> 
> main:
>         pushl   %ebp
>         pushl   %edi
>         pushl   %esi
>         pushl   %ebx
>         subl    _32, %esp
>         xorl    %ebp, %ebp
>         cmpl    _1, 52(%esp)
>         movl    _0, 20(%esp)
>         movl    _1000000, %edi      <----
>         movl    _1000000, 16(%esp)  <----
>         movl    _0, 12(%esp)
>         movl    _.LC27, 8(%esp)
>         je      .L274
>         movl    _1, %esi
>         cmpl    52(%esp), %esi
>         jge     .L272
> 
> No sane human will do that.
> 
> main:
>         pushl   %ebp
>         pushl   %edi
>         pushl   %esi
>         pushl   %ebx
>         subl    _32, %esp
>         xorl    %ebp, %ebp
>         cmpl    _1, 52(%esp)
>         movl    _0, 20(%esp)
>         movl    _1000000, %edi
>         movl    %edi, 16(%esp)	<-- save 4 bytes
>         movl    %ebp, 12(%esp)  <-- save 4 bytes
>         movl    _.LC27, 8(%esp)

Hmm, but gcc version is likely faster. No sane person would write
multiply by 5 using single lea instruction, yet gcc will do that...
				Pavel 
-- 
				Pavel
Written on sharp zaurus, because my Velo1 broke. If you have Velo you don't need...