[PATCH] D70366: Add new 'flatten' LLVM attribute to fix clang's 'flatten' function attribute

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith added a comment.

In D70366#1970758 <https://reviews.llvm.org/D70366#1970758>, @jdoerfert wrote:

> In D70366#1970526 <https://reviews.llvm.org/D70366#1970526>, @dexonsmith wrote:
>
> > In D70366#1970299 <https://reviews.llvm.org/D70366#1970299>, @LevitatingLion wrote:
> >
> > > Maybe we can add an additional string attribute when adding the noinline attribute to functions which are not marked noinline in the source code, something like "noinline-added-by-clang". I don't know if that's a legitimate use case for a string attribute, but it wouldn't be very invasive. What do you think?
> >
> >
> > Another option (not sure if it's better) would be to add a `noopt` LLVM attribute that Clang adds for `-O0` instead of `noinline`.  Two possibilities would be to update the inliner to pay attention to that as well (with special logic for `flatten`), or to change the always-inliner to add `noinline` to anything marked `noopt`.
>
>
> `noopt == optnone`? Both `optnone` and `noinline` are set in O0, so we could just not place `noinline` (I think).


Sure, that could work.  Or the noflatten idea is another possibility.  It would be good to hear what others think.


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