From: GAMMELJL AT SLU DOT EDU
Date: Tue, 25 Aug 1998 08:37:55 -0500 (CDT)
Subject: assembly language
To: djgpp AT delorie DOT com
Message-id: <01J10IURTRN694HU4A@SLU.EDU>
Organization: SAINT LOUIS UNIVERSITY  St. Louis, MO
MIME-version: 1.0
Precedence: bulk

     Thanks to those who responded to my query about
        movl $0x0,%edx    vs    xorl %edx,%edx
The movl sets %edx to zero, whereas xorl sets %edx and the carry bit to
zero.  Thus the two statements above are not exactly the same thing.
This fact could make little difference to all but a few programmers,
and those few probably already know to avoid the xorl command when
writing codes in assembly language.  I find that the movl command
results in faster executables even when xorl can be used as above
(in those cases in which the carry bit does not matter).