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[PATCH v2 5/9] x86: improve handling of insns with ambiguous operand sizes

Jan Beulich jbeulich@suse.com
Fri Nov 15 08:40:00 GMT 2019 
On 14.11.2019 20:16, H.J. Lu wrote:
> On Thu, Nov 14, 2019 at 1:00 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> On 13.11.2019 22:12,  H.J. Lu  wrote:
>>> What do you mean by improving AT&T syntax?  AT&T syntax has
>>> many quirks.  We should leave them alone if we can.
>>
>> May I kindly ask you to read the description of this patch again.
>> Current AT&T behavior is, as far as I'm concerned, intolerably
>> dangerous (and in the course of putting together this change
>> over the last couple of years it has helped point out actual
>> mistakes in other projects that I've been building with early
>> versions of this change in place).
>>
> 
> The default size is one of quirks.  Changing it can make previously
> working assembly codes stop working.  If one is writing the new
> assembly codes in AT&T syntax, she/he should avoid default size
> when in doubt.   We can add a command-line switch to check these
> quirks.

I.e. you want to effectively tell people that PUSH/POP/PUSHF/POPF
etc _have_ to have suffixes in AT&T mode? Personally I wouldn't
expect this to be well received - to me, the more suffixes can
be omitted without risking wrong code generation, the better for
readability. Arguably this may be influenced by me having grown
up with Intel syntax, and hence considering suffixes to harm
readability, but anyway.

In any even - I'll see about finding time to investigate in how
far I can sensibly avoid at least some of the DefaultSize
additions.

Jan
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