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

Renato Golin via llvm-dev
Wed, 09 Sep 2020 17:28:32 -0000

On Wed, 9 Sep 2020 at 18:15, Min-Yih Hsu via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> David mentioned in D87337 that LLVM has used similar techniques on code
> size (not sure what he was referencing, my guess will be something related
> to hot-cold code splitting).
>

IIUC, it's just using optsize instead of optnone. The idea is that, if the
code really doesn't run often/at all, then the performance impact of
reducing the size is negligible, but the size impact is considerable.

I'd wager that optsize could even be faster than optnone, as it would
delete a lot of useless code... but not noticeable, as it wouldn't run much.

This is an idea that we (Verona Language) are interested in, too.
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