Make std::get_temporary_buffer respect overaligned types when possible

Patch by Chris Kennelly!

Differential Revision: https://reviews.llvm.org/D41746

llvm-svn: 324020
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 4e3195c9b37dea4a945480576ace65986a56b773
diff --git a/include/memory b/include/memory
index 2273731..2d9d75f 100644
--- a/include/memory
+++ b/include/memory
@@ -2004,7 +2004,38 @@
         __n = __m;
     while (__n > 0)
     {
+#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
+#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+        if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+#else
+        if (std::alignment_of<_Tp>::value >
+            std::alignment_of<std::max_align_t>::value)
+#endif
+        {
+            std::align_val_t __al =
+                std::align_val_t(std::alignment_of<_Tp>::value);
+            __r.first = static_cast<_Tp*>(::operator new(
+                __n * sizeof(_Tp), __al, nothrow));
+        } else {
+            __r.first = static_cast<_Tp*>(::operator new(
+                __n * sizeof(_Tp), nothrow));
+        }
+#else
+#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+        if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+#else
+        if (std::alignment_of<_Tp>::value >
+            std::alignment_of<std::max_align_t>::value)
+#endif
+        {
+            // Since aligned operator new is unavailable, return an empty
+            // buffer rather than one with invalid alignment.
+            return __r;
+        }
+
         __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
+#endif
+
         if (__r.first)
         {
             __r.second = __n;
@@ -2017,7 +2048,23 @@
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-void return_temporary_buffer(_Tp* __p) _NOEXCEPT {::operator delete(__p);}
+void return_temporary_buffer(_Tp* __p) _NOEXCEPT
+{
+#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
+#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+    if (std::alignment_of<_Tp>::value > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+#else
+    if (std::alignment_of<_Tp>::value >
+        std::alignment_of<std::max_align_t>::value)
+#endif
+    {
+        std::align_val_t __al = std::align_val_t(std::alignment_of<_Tp>::value);
+        ::operator delete(__p, __al);
+        return;
+    }
+#endif
+    ::operator delete(__p);
+}
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template <class _Tp>