[PATCH] x86: Warn .insn instruction with length > 15 bytes

[Michael Matz]

Hello,

On Tue, 6 Feb 2024, H.J. Lu wrote:

> > > We issue a warning when something is wrong in input, but still manage
> > > to generate an instruction.   This is an error case.
> >
> > I disagree. It was a warning until you changed it (without me really
> > agreeing), and some hypothetical vendor could come and lift the limit,
> > on precisely the basis that there are legal encodings exceeding it. I'm
> > okay if this can be forced to be an error, but I continue to think that
> > it ought to be a warning only by default.
> >
> 
> It is an error on both Intel and AMD processors.   There is no
> valid reason not to be an error at the moment.

Jan gave you one.  I would prefer for the assembler to not be anally 
retentive.  An error that can be disabled is completely enough for this.

(I would wish for a general demote-all-errors-to-warnings option, like we 
already have a promote-all-warnings-to-errors; but lacking this an option 
to merely disable "errors" for avoiding specific random hardware behaviour 
would be fine as well)


Ciao,
Michael.