[PATCH] D77038: Fix bug in BitVector DenseMap hashing

[Brad Moody via Phabricator via llvm-commits]

bmoody created this revision.
bmoody added a reviewer: zturner.
Herald added a subscriber: dexonsmith.
Herald added a project: LLVM.

BitVectors with equal contents but different capacities were getting
different hashes. This also changes the behaviour of BitVector::getData
to only return the in-use words in the allocated array, but it appears that
the hashing code was the only thing using getData.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77038

Files:
  llvm/include/llvm/ADT/BitVector.h
  llvm/unittests/ADT/BitVectorTest.cpp


Index: llvm/unittests/ADT/BitVectorTest.cpp
===================================================================
--- llvm/unittests/ADT/BitVectorTest.cpp
+++ llvm/unittests/ADT/BitVectorTest.cpp
@@ -1204,4 +1204,22 @@
   EXPECT_EQ(true, Set.erase(A));
   EXPECT_EQ(0U, Set.size());
 }
+
+/// Test that capacity doesn't affect hashing.
+TYPED_TEST(BitVectorTest, DenseMapHashing) {
+  using DMI = DenseMapInfo<TypeParam>;
+  {
+    TypeParam A;
+    A.resize(200);
+    A.set(100);
+
+    TypeParam B;
+    B.resize(200);
+    B.set(100);
+    B.reserve(1000);
+
+    EXPECT_EQ(DMI::getHashValue(A), DMI::getHashValue(B));
+  }
+}
+
 } // namespace
Index: llvm/include/llvm/ADT/BitVector.h
===================================================================
--- llvm/include/llvm/ADT/BitVector.h
+++ llvm/include/llvm/ADT/BitVector.h
@@ -759,7 +759,9 @@
   }
   bool isInvalid() const { return Size == (unsigned)-1; }
 
-  ArrayRef<BitWord> getData() const { return Bits; }
+  ArrayRef<BitWord> getData() const {
+    return Bits.take_front(NumBitWords(size()));
+  }
 
   //===--------------------------------------------------------------------===//
   // Portable bit mask operations.


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