[Bug gas/26685] Error: invalid register operand size for `movdir64b'

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26685

--- Comment #14 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Jan Beulich from comment #13)
> (In reply to H.J. Lu from comment #12)
> > (In reply to Jan Beulich from comment #11)
> > > (In reply to H.J. Lu from comment #10)
> > > > symbol(%rip) is similar to symbol and DISP.  There is no real register
> > > > in memory operand.
> > > 
> > > I disagree - the compiler ought to emit
> > > 
> > >   movdir64b       foo(%eip), %eax

This isn't necessary for x32.

> > > 
> > > or
> > > 
> > >   movdir64b       foo(%rip), %rax
> > 
> > This is wrong for x32.
> 
> You mean both, or (I assume) just the latter?
> 
> > > in this case, whatever fits the x32 model better. The compiler ought to in
> > > particular be aware that the register operand of this insn is
> > > address-size-prefix, not operand-size-/REX-prefix controlled.
> > 
> > There is no RIP register in GCC. It isn't a real register. GCC always
> > generate foo(%rip).
> 
> That's not interesting, it's a gcc internal thing how to arrange for correct
> code to be generated. At the insn template level it's only %<number> anyway.
> What is needed is some sort of flag to indicate that in this specific case
> it needs to be foo(%eip).

No, we don't want 0x67 prefix for RIP-relative addressing for x32.

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