[PATCH] [Review Request] Numbering SDNode to discard SmallPtrSet in selection DAG

[Benjamin Kramer]

  Some high level comments:

  - SmallPtrSet is usually O(1) but falls back to linear search when it's small. SmallPtrSet<64> is way too large, have you benchmarked with the small capacity lowered to 8 or 16? This of course adds malloc overhead in more cases but we might get away with it.

  If the above fails:
  - I really don't see the point of FlagVector. Why not just use a SmallVector (or SmallBitVector as we're only storing bools) and resize appropriately when it's used. In any case, the class does not belong in SmallVector.h.

http://llvm-reviews.chandlerc.com/D1129