Re: PROPOSAL: Extend inline asm syntax with size spec

Richard Biener
2018-10-10T08:36:01Z

On Wed, 10 Oct 2018, Borislav Petkov wrote:

> On Wed, Oct 10, 2018 at 03:03:25AM -0500, Segher Boessenkool wrote:
> > The code immediately after this makes it size 1, even for things like
> > asm(""), I suppose this works better for the inliner. But that's a detail
> > (and it might change); the description says "consider this asm as minimum
> > length and cost for inlining decisions", which works for either 0 or 1.
>
> Thanks for implementing this, much appreciated. If you need people to
> test stuff, lemme know.
>
> > You can think of it as meaning "we want this asm inlined always", and then
> > whether that actually happens depends on if the function around it is
> > inlined or not.
>
> My only concern is how we would catch the other extremity where the
> inline asm grows too big and we end up inlining it everywhere and thus
> getting fat. The 0day bot already builds tinyconfigs but we should be
> looking at vmlinux size growth too.

Well, it's like always-inline functions, you have to be careful
and _not_ put it everywhere... It's also somewhat different to
always-inline functions as those lose their special-ness once
inlined (the inlined body is properly accounted for size).

Richard.