[llvm] fb42d3a - [ADT] Fix bug in BitVector and SmallBitVector DenseMap hashing.

[Michael Kruse via llvm-commits]

Author: Brad Moody
Date: 2020-04-18T00:21:08-05:00
New Revision: fb42d3afad1d9f09bcb90680baa77a39ecb99140

URL: https://github.com/llvm/llvm-project/commit/fb42d3afad1d9f09bcb90680baa77a39ecb99140
DIFF: https://github.com/llvm/llvm-project/commit/fb42d3afad1d9f09bcb90680baa77a39ecb99140.diff

LOG: [ADT] Fix bug in BitVector and SmallBitVector DenseMap hashing.

BitVectors and SmallBitVectors with equal contents but different
capacities were getting different hashes.

Reviewed By: aganea

Differential Revision: https://reviews.llvm.org/D77038

Added: 
    

Modified: 
    llvm/include/llvm/ADT/BitVector.h
    llvm/include/llvm/ADT/SmallBitVector.h
    llvm/unittests/ADT/BitVectorTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/BitVector.h b/llvm/include/llvm/ADT/BitVector.h
index 89158f213110..a8d0f07af94a 100644
--- a/llvm/include/llvm/ADT/BitVector.h
+++ b/llvm/include/llvm/ADT/BitVector.h
@@ -759,7 +759,9 @@ class BitVector {
   }
   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.

diff  --git a/llvm/include/llvm/ADT/SmallBitVector.h b/llvm/include/llvm/ADT/SmallBitVector.h
index b7367d68bdae..14545e2b612d 100644
--- a/llvm/include/llvm/ADT/SmallBitVector.h
+++ b/llvm/include/llvm/ADT/SmallBitVector.h
@@ -668,8 +668,11 @@ class SmallBitVector {
   }
   bool isInvalid() const { return X == (uintptr_t)-1; }
 
-  ArrayRef<uintptr_t> getData() const {
-    return isSmall() ? makeArrayRef(X) : getPointer()->getData();
+  ArrayRef<uintptr_t> getData(uintptr_t &Store) const {
+    if (!isSmall())
+      return getPointer()->getData();
+    Store = getSmallBits();
+    return makeArrayRef(Store);
   }
 
 private:
@@ -717,8 +720,9 @@ template <> struct DenseMapInfo<SmallBitVector> {
     return V;
   }
   static unsigned getHashValue(const SmallBitVector &V) {
+    uintptr_t Store;
     return DenseMapInfo<std::pair<unsigned, ArrayRef<uintptr_t>>>::getHashValue(
-        std::make_pair(V.size(), V.getData()));
+        std::make_pair(V.size(), V.getData(Store)));
   }
   static bool isEqual(const SmallBitVector &LHS, const SmallBitVector &RHS) {
     if (LHS.isInvalid() || RHS.isInvalid())

diff  --git a/llvm/unittests/ADT/BitVectorTest.cpp b/llvm/unittests/ADT/BitVectorTest.cpp
index 7c9417966b16..efefd2b90be8 100644
--- a/llvm/unittests/ADT/BitVectorTest.cpp
+++ b/llvm/unittests/ADT/BitVectorTest.cpp
@@ -1204,4 +1204,34 @@ TYPED_TEST(BitVectorTest, DenseSet) {
   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));
+  }
+  {
+    TypeParam A;
+    A.resize(20);
+    A.set(10);
+
+    TypeParam B;
+    B.resize(20);
+    B.set(10);
+    B.reserve(1000);
+
+    EXPECT_EQ(DMI::getHashValue(A), DMI::getHashValue(B));
+  }
+}
+
 } // namespace