From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Meissner <meissner@osf.org>
To: hjl@nynexst.com
Cc: gas2@cygnus.com
Subject: An old gas bug
Date: Wed, 17 Aug 1994 06:08:00 -0000
Message-id: <9408171307.AA00342@pasta.osf.org>
References: <9408162303.AA17808@titanic.nynexst.com> <9408162303.AA17808@titanic.nynexst.com>
X-SW-Source: 1994/msg00070.html

| Hi,
| 
| This is a very old bug date back to 1.38.1. The reason no one really
| cares is gcc won't generate that kind of code, i.e., jump out of range.
| When some Linux people were working on X11R5, they used an Intel x86
| branch/loop instruction, jcxz, which has only byte displacements in
| the hand coded asm code. The AT&T as worked fine with expansion. But
| gas 1.38.1 generated some bogus codes. I fixed the bug for them. I
| think it is correct. The test case is very easy to produce. Please let
| me know if you need one.

While it should be certainly fixed in the assembler, the X11 code
should also replace the jcxz instruction with a compare against 0 and
jmp sequence, since that is faster on anything but an original 386.
See the optimization guides in the 486/pentium manuals.