[llvm] r354199 - Make Optional<T> Trivially Copyable when T is trivially copyable

[Serge Guelton via llvm-commits]

Author: serge_sans_paille
Date: Sat Feb 16 01:19:58 2019
New Revision: 354199

URL: http://llvm.org/viewvc/llvm-project?rev=354199&view=rev
Log:
Make Optional<T> Trivially Copyable when T is trivially copyable

This is another attempt in the process, works nicely on my setup,
let's check how it behaves on other targets.

Modified:
    llvm/trunk/include/llvm/ADT/Optional.h
    llvm/trunk/unittests/ADT/OptionalTest.cpp

Modified: llvm/trunk/include/llvm/ADT/Optional.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/Optional.h?rev=354199&r1=354198&r2=354199&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/Optional.h (original)
+++ llvm/trunk/include/llvm/ADT/Optional.h Sat Feb 16 01:19:58 2019
@@ -108,6 +108,59 @@ template <typename T, bool = is_triviall
     return reinterpret_cast<const T *>(storage.buffer);
   }
 };
+template <typename T> struct OptionalStorage<T, true> {
+  AlignedCharArrayUnion<T> storage;
+  bool hasVal = false;
+
+  OptionalStorage() = default;
+
+  OptionalStorage(const T &y) : hasVal(true) { new (storage.buffer) T(y); }
+  OptionalStorage(const OptionalStorage &O)  = default;
+  OptionalStorage(T &&y) : hasVal(true) {
+    new (storage.buffer) T(std::forward<T>(y));
+  }
+  OptionalStorage(OptionalStorage &&O) = default;
+
+  OptionalStorage &operator=(T &&y) {
+    if (hasVal)
+      *getPointer() = std::move(y);
+    else {
+      new (storage.buffer) T(std::move(y));
+      hasVal = true;
+    }
+    return *this;
+  }
+  OptionalStorage &operator=(OptionalStorage &&O) = default;
+
+  OptionalStorage &operator=(const T &y) {
+    if (hasVal)
+      *getPointer() = y;
+    else {
+      new (storage.buffer) T(y);
+      hasVal = true;
+    }
+    return *this;
+  }
+  OptionalStorage &operator=(const OptionalStorage &O) = default;
+
+  ~OptionalStorage() = default;
+
+  void reset() {
+    if (hasVal) {
+      (*getPointer()).~T();
+      hasVal = false;
+    }
+  }
+
+  T *getPointer() {
+    assert(hasVal);
+    return reinterpret_cast<T *>(storage.buffer);
+  }
+  const T *getPointer() const {
+    assert(hasVal);
+    return reinterpret_cast<const T *>(storage.buffer);
+  }
+};
 
 } // namespace optional_detail
 

Modified: llvm/trunk/unittests/ADT/OptionalTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/OptionalTest.cpp?rev=354199&r1=354198&r2=354199&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/OptionalTest.cpp (original)
+++ llvm/trunk/unittests/ADT/OptionalTest.cpp Sat Feb 16 01:19:58 2019
@@ -14,8 +14,15 @@
 
 #include <array>
 
+
 using namespace llvm;
 
+static_assert(llvm::is_trivially_copyable<Optional<int>>::value,
+              "trivially copyable");
+
+static_assert(llvm::is_trivially_copyable<Optional<std::array<int, 3>>>::value,
+              "trivially copyable");
+
 namespace {
 
 struct NonDefaultConstructible {