Assemble something like this:
movl 0(%edi),%eax
An explicit zero byte of displacment is being emitted into the code making this
a 3 byte instruction rather than two bytes. The latest source I examined
looked like this was probably somewhat easy to fix in the instruction emitter
by just checking if a displacement was included (and zero) then whacking the
disp field pointer to null, or something along those lines. That should keep
the existing "fake EBP 0" logic pretty intact and unaffected.
A lot of app header files I've seen seemed to use explicit zeros like above for
clarity reasons when there are a series of related displacements, or to make
the code line up nice on the page, etc. What tipped me off on this was I saw
the explicit zero displacement show up in an ASM listings of some of the Linux
387 emulator code and it jumped out at me.
--
Summary: Superfluous 0 displacment added in x86 code
Product: binutils
Version: unspecified
Status: NEW
Severity: enhancement
Priority: P2
Component: gas
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: cutaway at bellsouth dot net
CC: bug-binutils at gnu dot org
http://sources.redhat.com/bugzilla/show_bug.cgi?id=976
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