Allow llvm::Optional to work with types without default constructors.

This generalizes Optional to require less from the T type by using aligned
storage for backing & placement new/deleting the T into it when necessary.

Also includes unit tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175580 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 221 insertions, 11 deletions

diff --git a/include/llvm/ADT/Optional.h b/include/llvm/ADT/Optional.h
index 6f58ffa..cc6065c 100644
--- a/include/llvm/ADT/Optional.h
+++ b/include/llvm/ADT/Optional.h
@@ -17,6 +17,7 @@
 #define LLVM_ADT_OPTIONAL_H
 
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/AlignOf.h"
 #include <cassert>
 
 #if LLVM_HAS_RVALUE_REFERENCES
@@ -27,14 +28,22 @@ namespace llvm {
 
 template<typename T>
 class Optional {
-  T x;
+  AlignedCharArrayUnion<T> storage;
   bool hasVal;
 public:
-  explicit Optional() : x(), hasVal(false) {}
-  Optional(const T &y) : x(y), hasVal(true) {}
+  explicit Optional() : hasVal(false) {}
+  Optional(const T &y) : hasVal(true) {
+    new (storage.buffer) T(y);
+  }
+  Optional(const Optional &O) : hasVal(O.hasVal) {
+    if (hasVal)
+      new (storage.buffer) T(*O);
+  }
 
 #if LLVM_HAS_RVALUE_REFERENCES
-  Optional(T &&y) : x(std::forward<T>(y)), hasVal(true) {}
+  Optional(T &&y) : hasVal(true) {
+    new (storage.buffer) T(std::forward<T>(y));
+  }
 #endif
 
   static inline Optional create(const T* y) {
@@ -42,22 +51,49 @@ public:
   }
 
   Optional &operator=(const T &y) {
-    x = y;
-    hasVal = true;
+    if (hasVal)
+      **this = y;
+    else {
+      new (storage.buffer) T(y);
+      hasVal = true;
+    }
+    return *this;
+  }
+
+  Optional &operator=(const Optional &O) {
+    if (!O)
+      Reset();
+    else
+      *this = *O;
     return *this;
   }
+
+  void Reset() {
+    if (hasVal) {
+      (*this)->~T();
+      hasVal = false;
+    }
+  }
+
+  ~Optional() {
+    Reset();
+  }
   
-  const T* getPointer() const { assert(hasVal); return &x; }
-  const T& getValue() const LLVM_LVALUE_FUNCTION { assert(hasVal); return x; }
+  const T* getPointer() const { assert(hasVal); return reinterpret_cast<const T*>(storage.buffer); }
+  T* getPointer() { assert(hasVal); return reinterpret_cast<T*>(storage.buffer); }
+  const T& getValue() const LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
+  T& getValue() LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
 
   operator bool() const { return hasVal; }
   bool hasValue() const { return hasVal; }
   const T* operator->() const { return getPointer(); }
-  const T& operator*() const LLVM_LVALUE_FUNCTION { assert(hasVal); return x; }
+  T* operator->() { return getPointer(); }
+  const T& operator*() const LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
+  T& operator*() LLVM_LVALUE_FUNCTION { assert(hasVal); return *getPointer(); }
 
 #if LLVM_HAS_RVALUE_REFERENCE_THIS
-  T&& getValue() && { assert(hasVal); return std::move(x); }
-  T&& operator*() && { assert(hasVal); return std::move(x); } 
+  T&& getValue() && { assert(hasVal); return std::move(*getPointer()); }
+  T&& operator*() && { assert(hasVal); return std::move(*getPointer()); }
 #endif
 };
 
diff --git a/unittests/ADT/CMakeLists.txt b/unittests/ADT/CMakeLists.txt
index 0f39e02..9aad793 100644
--- a/unittests/ADT/CMakeLists.txt
+++ b/unittests/ADT/CMakeLists.txt
@@ -19,6 +19,7 @@ set(ADTSources
   IntervalMapTest.cpp
   IntrusiveRefCntPtrTest.cpp
   MapVectorTest.cpp
+  OptionalTest.cpp
   PackedVectorTest.cpp
   SCCIteratorTest.cpp
   SmallPtrSetTest.cpp
diff --git a/unittests/ADT/OptionalTest.cpp b/unittests/ADT/OptionalTest.cpp
new file mode 100644
index 0000000..8bdea45
--- /dev/null
+++ b/unittests/ADT/OptionalTest.cpp
@@ -0,0 +1,173 @@
+//===- llvm/unittest/ADT/OptionalTest.cpp - Optional unit tests -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "gtest/gtest.h"
+#include "llvm/ADT/Optional.h"
+using namespace llvm;
+
+namespace {
+
+struct NonDefaultConstructible {
+  static unsigned CopyConstructions;
+  static unsigned Destructions;
+  static unsigned CopyAssignments;
+  explicit NonDefaultConstructible(int) {
+  }
+  NonDefaultConstructible(const NonDefaultConstructible&) {
+    ++CopyConstructions;
+  }
+  NonDefaultConstructible &operator=(const NonDefaultConstructible&) {
+    ++CopyAssignments;
+    return *this;
+  }
+  ~NonDefaultConstructible() {
+    ++Destructions;
+  }
+  static void ResetCounts() {
+    CopyConstructions = 0;
+    Destructions = 0;
+    CopyAssignments = 0;
+  }
+};
+
+unsigned NonDefaultConstructible::CopyConstructions = 0;
+unsigned NonDefaultConstructible::Destructions = 0;
+unsigned NonDefaultConstructible::CopyAssignments = 0;
+
+// Test fixture
+class OptionalTest : public testing::Test {
+};
+
+TEST_F(OptionalTest, NonDefaultConstructibleTest) {
+  Optional<NonDefaultConstructible> O;
+  EXPECT_FALSE(O);
+}
+
+TEST_F(OptionalTest, ResetTest) {
+  NonDefaultConstructible::ResetCounts();
+  Optional<NonDefaultConstructible> O(NonDefaultConstructible(3));
+  EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+  NonDefaultConstructible::ResetCounts();
+  O.Reset();
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, InitializationLeakTest) {
+  NonDefaultConstructible::ResetCounts();
+  Optional<NonDefaultConstructible>(NonDefaultConstructible(3));
+  EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(2u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, CopyConstructionTest) {
+  NonDefaultConstructible::ResetCounts();
+  {
+    Optional<NonDefaultConstructible> A(NonDefaultConstructible(3));
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+    Optional<NonDefaultConstructible> B(A);
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+  }
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(2u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, ConstructingCopyAssignmentTest) {
+  NonDefaultConstructible::ResetCounts();
+  {
+    Optional<NonDefaultConstructible> A(NonDefaultConstructible(3));
+    Optional<NonDefaultConstructible> B;
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+    B = A;
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+  }
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(2u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, CopyingCopyAssignmentTest) {
+  NonDefaultConstructible::ResetCounts();
+  {
+    Optional<NonDefaultConstructible> A(NonDefaultConstructible(3));
+    Optional<NonDefaultConstructible> B(NonDefaultConstructible(4));
+    EXPECT_EQ(2u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(2u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+    B = A;
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+  }
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(2u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, DeletingCopyAssignmentTest) {
+  NonDefaultConstructible::ResetCounts();
+  {
+    Optional<NonDefaultConstructible> A;
+    Optional<NonDefaultConstructible> B(NonDefaultConstructible(3));
+    EXPECT_EQ(1u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+    B = A;
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(1u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+  }
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+}
+
+TEST_F(OptionalTest, NullCopyConstructionTest) {
+  NonDefaultConstructible::ResetCounts();
+  {
+    Optional<NonDefaultConstructible> A;
+    Optional<NonDefaultConstructible> B;
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+    B = A;
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+    EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+    EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+    NonDefaultConstructible::ResetCounts();
+  }
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyConstructions);
+  EXPECT_EQ(0u, NonDefaultConstructible::CopyAssignments);
+  EXPECT_EQ(0u, NonDefaultConstructible::Destructions);
+}
+
+} // end anonymous namespace
+