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Re: [PATCH] x86: Add .nop directive to assembler
On Mon, Feb 19, 2018 at 6:17 AM, Michael Matz <firstname.lastname@example.org> wrote:
> On Mon, 19 Feb 2018, Maciej W. Rozycki wrote:
>> > OK, except for one quibble with the default md_generate_nops. I think
>> > that should error rather than filling with zeros (which is likely to
>> > be an illegal instruction or trap).
>> I have a feeling the default should wire in HANDLE_ALIGN somehow. For
>> many targets, such as fixed instruction width RISC processors, there is
>> only going to be one way of filling a given amount of space with no-op
>> instructions, so I think there's no point in having code duplication
>> here. And even if there are more ways possible for a given target, then
>> the `.align' way is still right even if suboptimal.
> How would you propose to express "I need three nop
> instructions aka 12 bytes from here" with just .align? (Note: no matter
> how "here" is currently aligned!)
.align isn't the same as .nop. However, HANDLE_ALIGN can be updated
to shared the same code with md_generate_nops, like what I did for x86.