[LLVMdev] [RFC] Stripping unusable intrinsics

[Reid Kleckner]

On Sat, Dec 20, 2014 at 10:18 AM, Alex Rosenberg <alexr at leftfield.org>
wrote:

> This seems to indicate that the idea is a workable solution to your use
> case.
>
> We've still got some bikesheds to get through. (And I don't consider
> myself a good reviewer for Clang in this, so we need to identify who is.)
>

The patch looks pretty reasonable. You should send it to Aaron Ballman,
too. He's been doing all the Clang attribute machinery refactoring to make
them easy.

As background to this extension idea, let me say that I prefer the notion
> that developers, particularly perf-aware developers like gamedevs, will
> want to handle PGO via markup. The idea is for them to turn PGO
> measurements into consciously-chosen markup, since a given test run may not
> be fully expressive. (e.g. They may not play the whole game through each
> time.)
>
> So the idea is to have the enum be marked with a weight instead of just
> "impossible." The impossible value would be perhaps -inf. I'd suggest that
> weights could be either float 0 to 1 or 0 to 100, whichever works best with
> the PGO infrastructure.
>

Personally, I don't think we need to conflate impossible and improbable.
They seem different enough to warrant a second attribute. A separate
"enum_probability" attribute is interesting, though.
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