From fe03508abd5da11db43565b7bfbc62969730203d Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Wed, 3 Dec 2014 04:45:09 +0000
Subject: [PATCH] ADT: Add SmallVector<>::emplace_back()

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223201 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/ADT/SmallVector.h    |  45 ++++++++++
 unittests/ADT/SmallVectorTest.cpp | 131 ++++++++++++++++++++++++++++++
 2 files changed, 176 insertions(+)

diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h
index 21175413f09..8c29f5c498d 100644
--- a/include/llvm/ADT/SmallVector.h
+++ b/include/llvm/ADT/SmallVector.h
@@ -236,6 +236,51 @@ public:
     this->setEnd(this->end()-1);
     this->end()->~T();
   }
+
+#if LLVM_HAS_VARIADIC_TEMPLATES
+  template <typename... ArgTypes> void emplace_back(ArgTypes &&... Args) {
+    if (LLVM_UNLIKELY(this->EndX >= this->CapacityX))
+      this->grow();
+    ::new ((void *)this->end()) T(std::forward<ArgTypes>(Args)...);
+    this->setEnd(this->end() + 1);
+  }
+#else
+private:
+  template <typename Constructor> emplace_back_impl(Constructor emplace) {
+    if (LLVM_UNLIKELY(this->EndX >= this->CapacityX))
+      this->grow();
+    emplace((void *)this->end());
+    this->setEnd(this->end() + 1);
+  }
+
+public:
+  void emplace_back() {
+    emplace_back_impl([](void *Mem) { ::new (Mem) T(); });
+  }
+  template <typename T1> void emplace_back(T1 &&A1) {
+    emplace_back_impl([&](void *Mem) { ::new (Mem) T(std::forward<T1>(A1)); });
+  }
+  template <typename T1, typename T2> void emplace_back(T1 &&A1, T2 &&A2) {
+    emplace_back_impl([&](void *Mem) {
+      ::new (Mem) T(std::forward<T1>(A1), std::forward<T2>(A2));
+    });
+  }
+  template <typename T1, typename T2, typename T3>
+  void emplace_back(T1 &&A1, T2 &&A2, T3 &&A3) {
+    T(std::forward<T1>(A1), std::forward<T2>(A2), std::forward<T3>(A3));
+    emplace_back_impl([&](void *Mem) {
+      ::new (Mem)
+          T(std::forward<T1>(A1), std::forward<T2>(A2), std::forward<T3>(A3));
+    });
+  }
+  template <typename T1, typename T2, typename T3, typename T4>
+  void emplace_back(T1 &&A1, T2 &&A2, T3 &&A3, T4 &&A4) {
+    emplace_back_impl([&](void *Mem) {
+      ::new (Mem) T(std::forward<T1>(A1), std::forward<T2>(A2),
+                    std::forward<T3>(A3), std::forward<T4>(A4));
+    });
+  }
+#endif // LLVM_HAS_VARIADIC_TEMPLATES
 };
 
 // Define this out-of-line to dissuade the C++ compiler from inlining it.
diff --git a/unittests/ADT/SmallVectorTest.cpp b/unittests/ADT/SmallVectorTest.cpp
index 95bf33e5bfb..a18785af254 100644
--- a/unittests/ADT/SmallVectorTest.cpp
+++ b/unittests/ADT/SmallVectorTest.cpp
@@ -699,4 +699,135 @@ TEST(SmallVectorTest, MidInsert) {
     EXPECT_TRUE(m.hasValue);
 }
 
+enum EmplaceableArgState {
+  EAS_Defaulted,
+  EAS_Arg,
+  EAS_LValue,
+  EAS_RValue,
+  EAS_Failure
+};
+template <int I> struct EmplaceableArg {
+  EmplaceableArgState State;
+  EmplaceableArg() : State(EAS_Defaulted) {}
+  EmplaceableArg(EmplaceableArg &&X)
+      : State(X.State == EAS_Arg ? EAS_RValue : EAS_Failure) {}
+  EmplaceableArg(EmplaceableArg &X)
+      : State(X.State == EAS_Arg ? EAS_LValue : EAS_Failure) {}
+
+  explicit EmplaceableArg(bool) : State(EAS_Arg) {}
+
+private:
+  EmplaceableArg(const EmplaceableArg &X) LLVM_DELETED_FUNCTION;
+  EmplaceableArg &operator=(EmplaceableArg &&) LLVM_DELETED_FUNCTION;
+  EmplaceableArg &operator=(const EmplaceableArg &) LLVM_DELETED_FUNCTION;
+};
+
+enum EmplaceableState { ES_Emplaced, ES_Moved };
+struct Emplaceable {
+  EmplaceableArg<0> A0;
+  EmplaceableArg<1> A1;
+  EmplaceableArg<2> A2;
+  EmplaceableArg<3> A3;
+  EmplaceableState State;
+
+  Emplaceable() : State(ES_Emplaced) {}
+
+  template <class A0Ty>
+  explicit Emplaceable(A0Ty &&A0)
+      : A0(std::forward<A0Ty>(A0)), State(ES_Emplaced) {}
+
+  template <class A0Ty, class A1Ty>
+  Emplaceable(A0Ty &&A0, A1Ty &&A1)
+      : A0(std::forward<A0Ty>(A0)), A1(std::forward<A1Ty>(A1)),
+        State(ES_Emplaced) {}
+
+  template <class A0Ty, class A1Ty, class A2Ty>
+  Emplaceable(A0Ty &&A0, A1Ty &&A1, A2Ty &&A2)
+      : A0(std::forward<A0Ty>(A0)), A1(std::forward<A1Ty>(A1)),
+        A2(std::forward<A2Ty>(A2)), State(ES_Emplaced) {}
+
+  template <class A0Ty, class A1Ty, class A2Ty, class A3Ty>
+  Emplaceable(A0Ty &&A0, A1Ty &&A1, A2Ty &&A2, A3Ty &&A3)
+      : A0(std::forward<A0Ty>(A0)), A1(std::forward<A1Ty>(A1)),
+        A2(std::forward<A2Ty>(A2)), A3(std::forward<A3Ty>(A3)),
+        State(ES_Emplaced) {}
+
+  Emplaceable(Emplaceable &&) : State(ES_Moved) {}
+  Emplaceable &operator=(Emplaceable &&) {
+    State = ES_Moved;
+    return *this;
+  }
+
+private:
+  Emplaceable(const Emplaceable &) LLVM_DELETED_FUNCTION;
+  Emplaceable &operator=(const Emplaceable &) LLVM_DELETED_FUNCTION;
+};
+
+TEST(SmallVectorTest, EmplaceBack) {
+  EmplaceableArg<0> A0(true);
+  EmplaceableArg<1> A1(true);
+  EmplaceableArg<2> A2(true);
+  EmplaceableArg<3> A3(true);
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back();
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A1.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A2.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A3.State == EAS_Defaulted);
+  }
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back(std::move(A0));
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_RValue);
+    EXPECT_TRUE(V.back().A1.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A2.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A3.State == EAS_Defaulted);
+  }
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back(A0);
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_LValue);
+    EXPECT_TRUE(V.back().A1.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A2.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A3.State == EAS_Defaulted);
+  }
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back(A0, A1);
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_LValue);
+    EXPECT_TRUE(V.back().A1.State == EAS_LValue);
+    EXPECT_TRUE(V.back().A2.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A3.State == EAS_Defaulted);
+  }
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back(std::move(A0), std::move(A1));
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_RValue);
+    EXPECT_TRUE(V.back().A1.State == EAS_RValue);
+    EXPECT_TRUE(V.back().A2.State == EAS_Defaulted);
+    EXPECT_TRUE(V.back().A3.State == EAS_Defaulted);
+  }
+  {
+    SmallVector<Emplaceable, 3> V;
+    V.emplace_back(std::move(A0), A1, std::move(A2), A3);
+    EXPECT_TRUE(V.size() == 1);
+    EXPECT_TRUE(V.back().State == ES_Emplaced);
+    EXPECT_TRUE(V.back().A0.State == EAS_RValue);
+    EXPECT_TRUE(V.back().A1.State == EAS_LValue);
+    EXPECT_TRUE(V.back().A2.State == EAS_RValue);
+    EXPECT_TRUE(V.back().A3.State == EAS_LValue);
+  }
 }
+
+} // end namespace