Re: Gas can't handle prefix generated by gcc

[Zack Weinberg <zack at codesourcery dot com>]

"H. J. Lu" <hjl@lucon.org> 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.

It's not just GCC that does this; take a look at the Linux kernel's
arch/i386 assembly files.

> I can write a patch. But who will review it?

Not me.

zw