[ifcnv] Add comment explaining why it's OK to duplicate convergent MIs in ifcnv.
[ifcnv] Add comment explaining why it's OK to duplicate convergent MIs in ifcnv.

Summary:
Also add a comment briefly explaining what ifcnv is.

No functional changes.

Reviewers: resistor

Subscribers: echristo, tra, llvm-commits

Differential Revision: http://reviews.llvm.org/D17430

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@261543 91177308-0d34-0410-b5e6-96231b3b80d8

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