[PATCH] D14829: [SLP] Vectorize gather-like idioms ending at non-consecutive loads.

[Nadav Rotem via llvm-commits]

nadav added a comment.

In http://reviews.llvm.org/D14829#307505, @mssimpso wrote:

> Hal,
>
> Thanks very much for the follow-up. Yes, I'm working on compile-time along with the type shrinking work I previously mentioned. I will post an updated revision soon.


@mssimpso, I don't think that this is the right approach. I think that this should be handled in SelectionDAG, and not in the SLP vectorizer. Your measurements show that there are no performance gains on Spec2000 (and the performance test suite?). Every new heuristic/scan that we add to the SLP vectorizer increases the compile times, and I don't think that adding code to scan loads and start a vec-tree at the load roots is a good heuristic. Many people are using LLVM as a JIT compiler and these people care deeply about compile times. I don't think that in the general case there are many opportunities for vectorization when you search from the address of loads, and I think that your measurements show that this is indeed the case. If you care about the specific pattern of load/store then you can optimize this in SelectionDAG.


http://reviews.llvm.org/D14829