Interface user provided vector functions with the vectorizer.

Greetings,

I am working on implementing the proposal in this thread. Please find the patch for review - [Login].

This first patch implements the SVFS(Search Vector Function System), with the interface as described in the proposal. This initial patch will be followed by another one that expose the SVFS via an analysis pass.

I kindly ask for feedback from everyone involved in this discussion. For now, I have added Simon Moll and Johannes Doerfert as reviewers, as they asked explicitly to be added.

Thank you.

Greetings,

As suggested in the previous review, I have now split my work into two separate patches.

I kindly ask for feedback from everyone involved in this discussion. I encourage others as well to be a part of this review process.

Please find the following patches for review -
[https://reviews.llvm.org/D66024\] - Name Demangling as specified in the Vector Function ABI
[https://reviews.llvm.org/D66025\] - SVFS implementation according to RFC: Interface user provided vector functions with the vectorizer. Builds on top of the previous patch.

Thank you.