[cfe-dev] [llvm-dev] [RFC] New Feature Proposal: De-Optimizing Cold Functions using PGO Info

[Renato Golin via cfe-dev]

On Thu, 10 Sep 2020 at 18:22, Min-Yih Hsu <minyihh at uci.edu> wrote:

> I totally agree with Wenlei that (somewhere in the future) we should have
> a unified FDO framework for both code size and compilation time. And I
> think Renato and Tobias's suggestions to do the same thing for
> size-oriented attributes (i.e. `minsize` and `optsize`) is the
> low-hanging fruit we can support in a short time.
> Engineering-wised I'll prefer to send out a separate review for the
> size-oriented attributes work, since `minsize` / `optsize` are kind of in
> conflict with `optnone` so I don't think it's a good idea to put them into
> one flag / feature set.
>

I'm happy for this unification to happen at a later stage. Just not too
long later.

I worry exposing the flags will get people to use it and then we'll change
it. The longer we leave it, the more people will be hit by the subtle
change.

Worse still if we release with one behaviour now and then with a different
behaviour in the next release.

Having conditional paths in build systems for different versions of the
compiler isn't fun.

--renato
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