[PATCH] LowerBitSets: Use byte arrays instead of bit sets to represent in-memory bit sets.

[Kostya Serebryany]

================
Comment at: include/llvm/Transforms/IPO/LowerBitSets.h:34
@@ -35,1 +33,3 @@
+  // The indices of the set bits in the bitset.
+  std::set<uint64_t> Bits;
 
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Is this better than unordered_set?
(I don't know, just asking)

================
Comment at: include/llvm/Transforms/IPO/LowerBitSets.h:183
@@ +182,3 @@
+  /// set. AllocByteOffset is set to the offset within the byte array and
+  /// AllocMask is set to the bitmask for those bits. This uses the LPT
+  /// multiprocessor scheduling algorithm to lay out the bits efficiently;
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LPT == longest process time? 
Maybe mention the full name here? 

================
Comment at: lib/Transforms/IPO/LowerBitSets.cpp:34
@@ -33,3 +33,3 @@
 
-STATISTIC(NumBitSetsCreated, "Number of bitsets created");
+STATISTIC(NumByteArraysCreated, "Number of byte arrays created");
 STATISTIC(NumBitSetCallsLowered, "Number of bitset calls lowered");
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It would be interesting to see more details stats here, 
e.g. how many bits were packed into how many bytes.

http://reviews.llvm.org/D7954

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