Give SmallPtrSet move semantics when we have R-value references.

Somehow, this ADT got missed which is moderately terrifying considering
the efficiency of move for it.

The code to implement move semantics for it is pretty horrible
currently but was written to reasonably closely match the rest of the
code. Unittests that cover both copying and moving (at a basic level)
added.

llvm-svn: 195239

llvm/include/llvm/ADT/SmallPtrSet.h

@@ -60,8 +60,12 @@ protected:
   unsigned NumElements;
   unsigned NumTombstones;
 
-  // Helper to copy construct a SmallPtrSet.
-  SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl& that);
+  // Helpers to copy and move construct a SmallPtrSet.
+  SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that);
+#if LLVM_HAS_RVALUE_REFERENCES
+  SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
+                  SmallPtrSetImpl &&that);
+#endif
   explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize) :
     SmallArray(SmallStorage), CurArray(SmallStorage), CurArraySize(SmallSize) {
     assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
@@ -135,6 +139,9 @@ protected:
   void swap(SmallPtrSetImpl &RHS);
 
   void CopyFrom(const SmallPtrSetImpl &RHS);
+#if LLVM_HAS_RVALUE_REFERENCES
+  void MoveFrom(SmallPtrSetImpl &&RHS);
+#endif
 };
 
 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
@@ -242,6 +249,10 @@ class SmallPtrSet : public SmallPtrSetImpl {
 public:
   SmallPtrSet() : SmallPtrSetImpl(SmallStorage, SmallSizePowTwo) {}
   SmallPtrSet(const SmallPtrSet &that) : SmallPtrSetImpl(SmallStorage, that) {}
+#if LLVM_HAS_RVALUE_REFERENCES
+  SmallPtrSet(SmallPtrSet &&that)
+      : SmallPtrSetImpl(SmallStorage, SmallSizePowTwo, std::move(that)) {}
+#endif
 
   template<typename It>
   SmallPtrSet(It I, It E) : SmallPtrSetImpl(SmallStorage, SmallSizePowTwo) {
@@ -280,14 +291,20 @@ public:
     return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
   }
 
-  // Allow assignment from any smallptrset with the same element type even if it
-  // doesn't have the same smallsize.
-  const SmallPtrSet<PtrType, SmallSize>&
+  SmallPtrSet<PtrType, SmallSize> &
   operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
     CopyFrom(RHS);
     return *this;
   }
 
+#if LLVM_HAS_RVALUE_REFERENCES
+  SmallPtrSet<PtrType, SmallSize>&
+  operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
+    MoveFrom(std::move(RHS));
+    return *this;
+  }
+#endif
+
   /// swap - Swaps the elements of two sets.
   void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
     SmallPtrSetImpl::swap(RHS);

llvm/lib/Support/SmallPtrSet.cpp

@@ -186,6 +186,29 @@ SmallPtrSetImpl::SmallPtrSetImpl(const void **SmallStorage,
   NumTombstones = that.NumTombstones;
 }
 
+#if LLVM_HAS_RVALUE_REFERENCES
+SmallPtrSetImpl::SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
+                                 SmallPtrSetImpl &&that) {
+  SmallArray = SmallStorage;
+
+  // Copy over the basic members.
+  CurArraySize = that.CurArraySize;
+  NumElements = that.NumElements;
+  NumTombstones = that.NumTombstones;
+
+  // When small, just copy into our small buffer.
+  if (that.isSmall()) {
+    CurArray = SmallArray;
+    memcpy(CurArray, that.CurArray, sizeof(void *) * CurArraySize);
+    return;
+  }
+
+  // Otherwise, we steal the large memory allocation and no copy is needed.
+  CurArray = that.CurArray;
+  that.CurArray = that.SmallArray;
+}
+#endif
+
 /// CopyFrom - implement operator= from a smallptrset that has the same pointer
 /// type, but may have a different small size.
 void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
@@ -222,6 +245,27 @@ void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) {
   NumTombstones = RHS.NumTombstones;
 }
 
+#if LLVM_HAS_RVALUE_REFERENCES
+void SmallPtrSetImpl::MoveFrom(SmallPtrSetImpl &&RHS) {
+  if (!isSmall())
+    free(CurArray);
+
+  if (RHS.isSmall()) {
+    // Copy a small RHS rather than moving.
+    CurArray = SmallArray;
+    memcpy(CurArray, RHS.CurArray, sizeof(void*)*RHS.CurArraySize);
+  } else {
+    CurArray = RHS.CurArray;
+    RHS.CurArray = RHS.SmallArray;
+  }
+
+  // Copy the rest of the trivial members.
+  CurArraySize = RHS.CurArraySize;
+  NumElements = RHS.NumElements;
+  NumTombstones = RHS.NumTombstones;
+}
+#endif
+
 void SmallPtrSetImpl::swap(SmallPtrSetImpl &RHS) {
   if (this == &RHS) return;
 

llvm/unittests/ADT/SmallPtrSetTest.cpp

@@ -71,6 +71,55 @@ TEST(SmallPtrSetTest, GrowthTest) {
       EXPECT_EQ(1,buf[i]);
 }
 
+TEST(SmallPtrSetTest, CopyAndMoveTest) {
+  int buf[8];
+  for (int i = 0; i < 8; ++i)
+    buf[i] = 0;
+
+  SmallPtrSet<int *, 4> s1;
+  s1.insert(&buf[0]);
+  s1.insert(&buf[1]);
+  s1.insert(&buf[2]);
+  s1.insert(&buf[3]);
+  EXPECT_EQ(4U, s1.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s1.count(&buf[i]));
+    else
+      EXPECT_FALSE(s1.count(&buf[i]));
+
+  SmallPtrSet<int *, 4> s2(s1);
+  EXPECT_EQ(4U, s2.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s2.count(&buf[i]));
+    else
+      EXPECT_FALSE(s2.count(&buf[i]));
+
+  s1 = s2;
+  EXPECT_EQ(4U, s1.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s1.count(&buf[i]));
+    else
+      EXPECT_FALSE(s1.count(&buf[i]));
+
+  SmallPtrSet<int *, 4> s3(llvm_move(s1));
+  EXPECT_EQ(4U, s3.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s3.count(&buf[i]));
+    else
+      EXPECT_FALSE(s3.count(&buf[i]));
+
+  s1 = llvm_move(s3);
+  EXPECT_EQ(4U, s1.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s1.count(&buf[i]));
+    else
+      EXPECT_FALSE(s1.count(&buf[i]));
+}
 
 TEST(SmallPtrSetTest, SwapTest) {
   int buf[10];