From mboxrd@z Thu Jan  1 00:00:00 1970
From: mycroft@gnu.ai.mit.edu
To: dj@stealth.ctron.com
Cc: gas2@cygnus.com, hjl@nynexst.com, masaki@eie.minolta.co.jp, raeburn@cygnus.com
Subject: Re: [masaki@eie.monolta.co.jp: GAS bug and etc]
Date: Fri, 11 Nov 1994 13:42:00 -0000
Message-id: <9411112139.AA00683@goldman.gnu.ai.mit.edu>
X-SW-Source: 1994/msg00193.html

   The problem with using the 16-bit jcxz is that, even if the offset is
   small, if the target isn't in the first 64K of memory, the program is
   toast.  The reason is that %eip is masked to 0x0000ffff AFTER adding
   the offset.

The comment you're referring to:

rel16/32 indicates that these instructions map to two; one with a 16-bit
relative displacement, the other with a 32-bit relative displacement,
depending on the operand-size attribute of the instruction.

only applies to the `rel16/32' versions of the conditional jump
instructions.  The JCXZ and JECXZ instructions do not allow 16- or
32-bit displacements.

The `Operation' section for that instruction should be more clear.

BTW, why are you using JCXZ or JECXZ at all?  The equivalent sequence:

testl %ecx,%ecx
jz ...

is the same speed on the 386, but faster on the Pentium (and probably
the 486, but I don't have those timing specs).