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

[Hongyu Wang <wwwhhhyyy333@gmail.com>]

>    as_bad() is used to mark errors that result in what we
>    presume to be a useless object file.  Say, we ignored
>    something that might have been vital.
>    ...
>
>    as_warn() is used when we have an error from which we
>    have a plausible error recovery.  eg, masking the top
>    bits of a constant that is longer than will fit in the
>    destination.  In this case we will continue to assemble
>    the source, although we may have made a bad assumption,
>    and we will produce an object file and return normal exit
>    status (ie, no error).
>    ...
>
> It's obvious to me that just continuing to assemble the over-long
> instruction is a "plausible error recovery".  It's even more plausible
> than "masking the top bits of a constant".  Certainly an object file
> containing a byte sequence correspending to the overlong instruction is
> not "useless".

We have encountered such issue when running APX workloads with SDE.
The over-long instruction became either illegal or wrong instruction
when executing the program, then it crashes after long time running.
This definitely increases much effort for runtime diagnostics.
As the over-long instruction would actually break the program, say the
object crashes or returns with abnormal exit status, the default
should be an error for assembler and we can add an option to lower the
error to warning.