[PATCH] x86: Add .nop directive to assembler

H.J. Lu hjl.tools@gmail.com
Tue Feb 20 01:03:00 GMT 2018


On Mon, Feb 19, 2018 at 4:05 PM, Alan Modra <amodra@gmail.com> wrote:
> On Mon, Feb 19, 2018 at 03:24:17PM -0800, H.J. Lu wrote:
>> On Mon, Feb 19, 2018 at 3:19 PM, Alan Modra <amodra@gmail.com> wrote:
>> > On Mon, Feb 19, 2018 at 10:08:38PM +0000, Maciej W. Rozycki wrote:
>> >> On Mon, 19 Feb 2018, Alan Modra wrote:
>> >>
>> >> > > .nop is similar to .skip, except that it fills with NOPs.  Yes, it can be used
>> >> > > wherever .skip can be used.
>> >> >
>> >> > Given https://sourceware.org/ml/binutils/2018-02/msg00322.html I'm
>> >> > inclined to think the name of the directive should change.
>> >> > .skipnops perhaps?
>> >>
>> >>  Just `.nops' maybe?  There doesn't appear to be any matching mnemonic in
>> >> opcodes/.
>> >
>> > I'd be happy with that too.
>>
>> There is no guarantee that one of those NO_PSEUDO_DOT targets or the new
>> NO_PSEUDO_DOT target won't have an instruction called nops or skipnops in
>> the future.
>
> If a target adds an instruction like that, then the target will need
> to deal with it.  For example, as the spu target deals with "set" and
> "equ" which existed as directives before the spu defined them as
> instructions.
>
> In this case the use of "nop" as an instruction existed before you
> decided to define ".nop" as a directive, and lack of testing resulted
> in not discovering the NO_PSEUDO_DOT clash.  I suspect we wouldn't be
> having this conversation if you had run a full test suite regression,
> rather than just testing x86.  You yourself would have chosen
> something other than ".nop" as a directive!

I would have chosen .nop and handled it for NO_PSEUDO_DOT targets.

Here is a patch to rename .nop to .nops.  OK for master?

-- 
H.J.
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