[RFC] Adding a new attribute to function param to mark it as constant

[Segher Boessenkool]

On Wed, Aug 04, 2021 at 02:00:42PM +0100, Richard Earnshaw wrote:
> We don't want to have to resort to macros.  Not least because at some
> point we want to replace the content of arm_neon.h with a single #pragma
> directive to remove all the parsing of the header that's needed.  What's
> more, if we had a suitable pragma we'd stand a fighting chance of being
> able to extend support to other languages as well that don't use the
> pre-processor, such as Fortran or Ada (not that that is on the cards
> right now).

So how do you want to handle constants-that-are-not-yet-constant, say
before inlining?  And how do you want to deal with those possibly not
ever becoming constant, perhaps because you used a too low "n" in -On
(but there are very many random other causes)?  And, what *is* a
constant, anyway?  This is even more fuzzy if you consider those
other languages as well.

(Does skipping parsing of some trivial header save so much time?  Huh!)


Segher