On Thu, Nov 28, 2024 at 11:23:02AM +0100, Richard Biener wrote:
> Sorry for chiming in only late - to me this shows that the desire to inline
> a function more than another function, currently identified as
> DECL_DECLARED_INLINE_P overlaps with frontend semantic differences.
> But don't we reflect those semantic differences into the IL (via linkage,
> symtab details) already?
After handling it in the FE, yes, we do. We still want
DECL_DECLARED_INLINE_P also e.g. for debug info generation.
> So what would remain is a way for the user
> to distinguish between auto-inline (we have the corresponding -auto
> set of --params) and inline-inline. The middle-end interface after your
> change, where DECL_DECLARED_INLINE_P means inline-inline
> unless !DECL_OPTIMIZABLE_INLINE_P looks a bit awkward.
>
> Rather than clearing DECL_DECLARED_INLINE_P I'd suggest to
> split both completely and turn DECL_DISREGARD_INLINE_LIMITS,
> DECL_UNINLINABLE and auto-inline vs. inline-inline into a
> multi-bit enum and only use that for inlining decisions (ignoring
> DECL_DECLARED_INLINE_P for that purpose, but use that
> and feeble_inline to compute the enum value).
I think a 4 state flag { never_inline, default, auto_inline, always_inline }
would be fine. The question is how to call the macro(s) and values
and how to merge those from different decls and what we do currently
e.g. for noinline, always_inline, on the same or on different decls
of the same function.
> Note I've had to lookup what 'feeble' means - given we use -auto
feeble was used in the meaning of synonym to weak, as I wrote,
weak_inline could be confusing.
Another possibility would be weaker_inline though, that one can't
confuse with weak attribute.
> for --params I'd have chosen __attribute__((auto_inline)), possibly
> "completed" by __attribute__((inline)) to mark a function as
> wanting 'inline' heuristics but not 'inline' semantics.
I think auto_inline and inline would be just confusing, even in the negative
forms. We actually "auto-inline" even functions not declared inline, just
with different heuristics.
Jakub
