[Bug binutils/25445] movsxd without REX_W prefix incorrectly disassembled

[jbeulich at suse dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25445

--- Comment #5 from Jan Beulich <jbeulich at suse dot com> ---
(In reply to H.J. Lu from comment #4)
> (In reply to Jan Beulich from comment #3)
> > (In reply to H.J. Lu from comment #0)
> > >    0:     66 63 08                movslq (%rax),%cx
> > 
> > Looks correct to me.
> 
> movslq is AT&T syntax for 32 bits -> 64 bits. It isn't accepted by
> assembler.  movsxd should be here.

MOVSXD, like MOVSX and MOVZX, is Intel syntax, and hence has nothing to do in
AT&T syntax disassembly.

> > (In reply to H.J. Lu from comment #1)
> > > Also
> > > 
> > > 63 08                     movslq (%rax),%ecx
> > 
> > This too looks correct to me.
> 
> movsxd should be here.

Same here.

> > The only anomaly I can think of because of the vendor difference would be a
> > memory operand in Intel syntax mode, which - if tagged by an operand size -
> > might want to be WORD PTR for the 16-bit case in Intel64 mode and DWORD PTR
> > in the AMD64 one.
> 
> Manual can be wrong.  The current Intel manual says that MOVSXD is valid
> for 32-bit. Can you double check MOVSXD on AMD processor to verify
> 
> movsxd (%rax), %cx
> 
> does load 4 bytes?

I did already around the time I put together

https://sourceware.org/ml/binutils/2019-12/msg00347.html

Both manuals accurately describe actual hardware behavior.

-- 
You are receiving this mail because:
You are on the CC list for the bug.