[alignof] Put back the hack for old versions of GCC.

This works around a bug (PR56859) that is fixed in all versions of GCC I tested
with but was present in 4.8.0. Using 4.8.0 is of course a terrible idea, but looks
like we can't drop it just yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233916 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/AlignOf.h b/include/llvm/Support/AlignOf.h
index f30467d5440ded5ebbdd98c1cb805fed471c1d14..061d5acf2322b570ad197b753db150d10c2f1b4b 100644 (file)
--- a/include/llvm/Support/AlignOf.h
+++ b/include/llvm/Support/AlignOf.h
@@ -70,11 +70,38 @@ inline unsigned alignOf() { return AlignOf<T>::Alignment; }
 // MSVC requires special handling here.
 #ifndef _MSC_VER
 
+#if __has_feature(cxx_alignas)
 template<std::size_t Alignment, std::size_t Size>
 struct AlignedCharArray {
-  LLVM_ALIGNAS(Alignment) char buffer[Size];
+  alignas(Alignment) char buffer[Size];
 };
 
+#elif defined(__GNUC__) || defined(__IBM_ATTRIBUTES)
+/// \brief Create a type with an aligned char buffer.
+template<std::size_t Alignment, std::size_t Size>
+struct AlignedCharArray;
+
+#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
+  template<std::size_t Size> \
+  struct AlignedCharArray<x, Size> { \
+    __attribute__((aligned(x))) char buffer[Size]; \
+  };
+
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64)
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128)
+
+#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
+
+#else
+# error No supported align as directive.
+#endif
+
 #else // _MSC_VER
 
 /// \brief Create a type with an aligned char buffer.