/// integer literal can be used to specify an alignment constraint. Once built
/// up here, we can then begin to indirect between these using normal C++
/// template parameters.
-template <size_t Alignment> struct AlignedCharArrayImpl {};
-template <> struct AlignedCharArrayImpl<0> {
- typedef char type;
-};
-#if __cplusplus == 201103L || __has_feature(cxx_alignas)
-#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
- template <> struct AlignedCharArrayImpl<x> { \
- typedef char alignas(x) type; \
- }
-#elif defined(__clang__) || defined(__GNUC__)
+template <size_t Alignment> struct AlignedCharArrayImpl;
+
+// MSVC requires special handling here.
+#ifndef _MSC_VER
+
+#if __has_feature(cxx_alignas)
#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
template <> struct AlignedCharArrayImpl<x> { \
- typedef char type __attribute__((aligned(x))); \
+ char alignas(x) aligned; \
}
-#elif defined(_MSC_VER)
+#elif defined(__GNUC__) || defined(__IBM_ATTRIBUTES)
#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
template <> struct AlignedCharArrayImpl<x> { \
- typedef __declspec(align(x)) char type; \
+ char aligned __attribute__((aligned(x))); \
}
#else
# error No supported align as directive.
LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2048);
LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4096);
LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8192);
+
+#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
+
+#else // _MSC_VER
+
+// We provide special variations of this template for the most common
+// alignments because __declspec(align(...)) doesn't actually work when it is
+// a member of a by-value function argument in MSVC, even if the alignment
+// request is something reasonably like 8-byte or 16-byte.
+template <> struct AlignedCharArrayImpl<1> { char aligned; };
+template <> struct AlignedCharArrayImpl<2> { short aligned; };
+template <> struct AlignedCharArrayImpl<4> { int aligned; };
+template <> struct AlignedCharArrayImpl<8> { double aligned; };
+
+#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
+ template <> struct AlignedCharArrayImpl<x> { \
+ __declspec(align(x)) char aligned; \
+ }
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(512);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1024);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2048);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4096);
+LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8192);
// Any larger and MSVC complains.
#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
-/// \brief This class template exposes a typedef for type containing a suitable
-/// aligned character array to hold elements of any of up to four types.
+#endif // _MSC_VER
+
+/// \brief This union template exposes a suitably aligned and sized character
+/// array member which can hold elements of any of up to four types.
///
/// These types may be arrays, structs, or any other types. The goal is to
/// produce a union type containing a character array which, when used, forms
/// than four types can be added at the cost of more boiler plate.
template <typename T1,
typename T2 = char, typename T3 = char, typename T4 = char>
-class AlignedCharArray {
+union AlignedCharArrayUnion {
+private:
class AlignerImpl {
T1 t1; T2 t2; T3 t3; T4 t4;
};
public:
- // Sadly, Clang and GCC both fail to align a character array properly even
- // with an explicit alignment attribute. To work around this, we union
- // the character array that will actually be used with a struct that contains
- // a single aligned character member. Tests seem to indicate that both Clang
- // and GCC will properly register the alignment of a struct containing an
- // aligned member, and this alignment should carry over to the character
- // array in the union.
- union union_type {
- // This is the only member of the union which should be used by clients:
- char buffer[sizeof(SizerImpl)];
-
- // This member of the union only exists to force the alignment.
- struct {
- typename llvm::AlignedCharArrayImpl<AlignOf<AlignerImpl>::Alignment>::type
- nonce_inner_member;
- } nonce_member;
- };
+ /// \brief The character array buffer for use by clients.
+ ///
+ /// No other member of this union should be referenced. The exist purely to
+ /// constrain the layout of this character array.
+ char buffer[sizeof(SizerImpl)];
+
+private:
+ // Tests seem to indicate that both Clang and GCC will properly register the
+ // alignment of a struct containing an aligned member, and this alignment
+ // should carry over to the character array in the union.
+ llvm::AlignedCharArrayImpl<AlignOf<AlignerImpl>::Alignment> nonce_member;
};
} // end namespace llvm