Merging r354128 and r354131:
r354128 | courbet | 2019-02-15 13:58:06 +0100 (Fri, 15 Feb 2019) | 1 line
[MergeICmps][NFC] Improve doc.
r354131 | courbet | 2019-02-15 15:17:17 +0100 (Fri, 15 Feb 2019) | 15 lines
[MergeICmps] Make base ordering really deterministic.
The idea is that we now manipulate bases through a unsigned BaseID based on
order of appearance in the comparison chain rather than through the Value*.
Subscribers: mgrang, jfb, jdoerfert, llvm-commits, hans