[PATCH] D99444: [ADT] Introduce lazy unique iterator

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: bkramer, dexonsmith, dblaikie, rriddle.
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You sometimes want to only deal with unique values of an underlying range.
Manually maintaining a set of already-dealt-with elements is cumbersome.

This introduces a `unique_iterator` forward iterator,
which lazily(!) tracks the elements of the range that were pointed-at already,
and skips them afterwards.

I've added some basic tests and adjusted a few places to use it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D99444

Files:
  llvm/include/llvm/ADT/UniqueRange.h
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/unittests/ADT/IteratorTest.cpp

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