[PATCH] [PR20893] Change SelectionDAG's DbgValueMap to have set semantics (NFC)

[David Blaikie]

as for testing - assuming these duplicates get deduplicated elsewhere (could you explain where?) then I doubt there's much to test - this is then just a perf optimization, not a change in any semantics. Maybe dumping MI could be testable, but I'm not sure what the dumping options (& whether they're available in non-asserts builds, etc) are like.

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Comment at: lib/CodeGen/SelectionDAG/SelectionDAG.cpp:6180
@@ +6179,3 @@
+      if (*Val == *V) return;
+    Vals.push_back(V);
+  }
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Could 'Vals' be an actual set of SDDbgValue*s?

Are SDDbgValue*s inherently uniqued such that pointer identity would be sufficient? (or do you need that equality comparison added above? Which could hopefully be adjusted to < comparison (or hashing) for a set-like structure)

http://reviews.llvm.org/D5451