Add AMD znver5 RMPREAD instruction

[Jan Beulich]

On 12.11.2024 13:07, Kalvakuntla, Umesh wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
> 
> Attached patch adds znver5 RMPREAD instruction.
> Details of the instruction are available in public document  https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24594.pdf

gas/doc/c-i386.texi also wants updating.

With you adding to ZNVER5 in i386-gen.c, the 2.42 NEWS entry then wasn't
really correct. Imo it is thus even more so important that you actually
add a fresh entry there as well, indicating that support is now indeed
complete (assuming of course it really is).

What is the intended way of specifying a segment override for %rcx? That
operand being a plain register rather than a normal memory operand makes
this (once again) odd ("once again" because we have pre-existing similar
insns, e.g. MONITOR).

As to the opcode table entry with operands (sorry, replying to patches
sent inline would be easier): Which of the operands does an address size
override actually affect? %rcx holding a linear address, it would seem
more likely that that's what the override applies to. Depending on the
answer, and depending on whether RMPUPDATE is behaving the same in this
regard, that insn may also need correcting in the table (alongside
adjusting the entry to be added).

Jan