[PATCH] D57504: RFC: Prototype & Roadmap for vector predication in LLVM

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally added a comment.

In D57504#1723586 <https://reviews.llvm.org/D57504#1723586>, @simoll wrote:

> DevMtg Summary
>
> - There will be a separate RFC for the generalized pattern rewriting logic in LLVM-VP (see `PatternMatch.h`). We do this because it is useful for other efforts as well, eg to make the existing pattern rewrites in InstSimplify/Combine, DAGCombiner work also for constrained fp (@uweigand ) and complex arithmetic (@greened) . This may actually speedup things since we can pursue VP and generalized pattern match in parallel.


I'd like to rant a little bit to see if anyone agrees with my probably unpopular opinion...

Code explosion is the symptom, not the sickness. It's caused by using experimental intrinsics. Experimental intrinsics are a detriment to progress. They end up creating a ton more work and are designed to be inevitably replaced.

I do understand the desire for these intrinsics by some -- i.e. devs that don't care about these new features aren't impacted. I think that's short sighted though. Hiding complexity behind utility functions will be painful when debugging tough problems. And updating existing code to use pattern matchers is a lot of churn -- probably more churn than making the constructs first-class citizens.

IMHO, we'd be better off baking these new features into LLVM right from the start. These 3 topics are fairly significant features. It would be hard to argue that any one will go out of style in the foreseeable future...


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