[PATCH] D49362: [ThinLTO] Compute constant references

[Eugene Leviant via Phabricator via llvm-commits]

evgeny777 added a comment.

> My understanding of your patch is that there would be a 1-1 association between each bit in the RefAccessBits BitVector and ref edges on that same function

Correct. But we have RefEdgeList in a base class (GlobalValueSummary) and there could be references between 2 globals:

  static int Foo;
  static int *Bar = &Foo;

It doesn't make sense to have const attribute for such kind of references, because we need to know how `Bar` is accessed before we can say anything about `Foo`. 
That's why I put access bit list to derived class (FunctionSummary). IMO converting `std::vector<ValueInfo> refs;` to `std::vector<EdgeTy>` would be a waste of memory
(though not too big).

> If it is non-static to start with, but is globally read-only, then it can be imported as a local copy

This also implies internalizing global in the source module, correct?

> In order to do something with an opt pass, don't you also need global analysis during the thin link to ensure there are no writes anywhere?

True, but for some reason I thought that global var fixups to BC module would be easier to implement. I'll give "local copy" approach a try and see how it goes.


https://reviews.llvm.org/D49362