Re: [PATCH v3 10/10] x86-64: Intel64 adjustments for insns dealing with far pointers

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Jan 17, 2020 at 3:48 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 16.01.2020 21:24,  H.J. Lu  wrote:
> > We should improve gas documentation.  The current far branches
> > work fine.  Why bother to add new far branches without giving
> > developer a clue how to use them?
>
> That's the subject of CPU documentation, not that of any assembler.
> The current far branches "work fine" as far as they're being made
> accessible (encodable) by gas. The 64-bit forms Intel CPUs support
> didn't work fine at all (because one had to use hand crafted REX.W
> prefixes), as per Andrew's bug report. There's no difference here
> to the prior work you did to support the Intel64 / AMD64
> differences for certain other insns - you've simply made gas
> capable of properly encoding them in a vendor dependent manner.
> You didn't accompany this with any documentation explaining "how
> to use" these. If, retroactively, you think this should have been
> accompanied by such documentation, may I ask that you add such,

Yes, it is not very obvious how to use them, we should add some
documentation.   Which one do you have in mind?

> which will then allow me to see what I could (should as per your
> opinion) add for the corrected variants here? Recall - I _still_
> don't know what exactly you're after.
>
> This would then further allow me to know whether the remaining
> Intl64 / AMD64 differences that gas doesn't properly support yet
> will also need to be accompanied by doc updates when I get around
> to adjusting them.
>
> Jan



-- 
H.J.