Gas can't handle prefix generated by gcc

H. J. Lu
Sat Jul 24 18:45:00 GMT 2004

On Fri, Jul 23, 2004 at 04:36:57PM -0700, Zack Weinberg wrote:
> "H. J. Lu" <> writes:
> >> 1) Make GAS accept cs;je and do the right thing.
> >> 2) Prove that cs/je, rep/stosl, etc are acceptable to all i386
> >>    assemblers since time immemorial.
> >> 3) Write the GCC patch yourself.  And I will not review it.
> >> 
> >> And yes, those are in order of decreasing preference.
> >
> > ';' is a line terminator for assembler. Assembler won't see the string
> > of "cs;je" at all. I don't think adding such a hack for gcc is a good
> > idea.
> My idea of the Right Thing would be to recognize an instruction
> consisting only of a prefix opcode (any prefix opcode - not just
> segment overrides), and save it to be combined with the next one.
> That would handle "cs;je", "rep\n\tmovsl", and so on.

There can be up to 4 prefixes. I have no interests in working such a
hack, given that gas supports the current prefix syntax at least since
1998. If anyone is concerned about the possible problems, they should
use the proper prefix syntax supported by gas.


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