[PATCH] Add similar function merging to MergeFunctions

[Tobias von Koch]

  Oh right - didn't realise commits wasn't on there! Also CCing Nick.

  There has been some work on MergeFunctions recently by Stepan so it probably needs to be rebased.

  Stepan - are you still working on this? If I recall correctly, you were considering implementing similar function merging on top of your ordering-based approach. I currently don't have the resources to completely rewrite the patch. If we want to support similar function merging right now, I see two options:

  a) try and add this as-is to MergeFunctions but this would likely mean we can't do your ordering-based merging,
  b) split MergeFunctions into two passes, one for merging identical functions (it could use your faster algorithm) and another just for similar function merging (based on parts of this patch).

  It would be nice to get this into trunk, because the results are good and it is in active use by customers. We also have an upcoming paper at LCTES with a more thorough evaluation.

http://reviews.llvm.org/D2591