On Fri, Jun 07, 2013 at 02:30:10PM +0100, Michael Brown wrote: > On 07/06/13 14:22, Daniel P. Berrange wrote: > >This doesn't look right: > > > >- "addw $4, %%sp\n\t" ) > >+ "popl %%ebp\n\t" /* discard */ > >+ "popl %%ebp\n\t" /* gcc bug */ ) > > > >In the original patch it was > >- "addw $4, %%sp\n\t" ) > >+ "addw $4, %%sp\n\t" > >+ "popl %%ebp\n\t" ) > > > >You've accidentally transposed the 'addw' into a second 'popl'. > > That's deliberate: since %ebp is about to get overwritten anyway, we > can use it as a discard register for the "popl", which increments > %sp by 4 using only two bytes of code rather than three. > > You can see several other instances of this pattern within the codebase: > > git grep "pop.*discard"
Ok, I'll assume you're right since my assembler knowledge is tiny :-) Just wanted to make sure it wasn't an accidental typo. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ ipxe-devel mailing list ipxe-devel@lists.ipxe.org https://lists.ipxe.org/mailman/listinfo.cgi/ipxe-devel
