#include "llvm/Support/Compiler.h"
#include <cstddef>
+#include <type_traits>
namespace llvm {
-template <typename T>
+namespace detail {
+
+// For everything other than an abstract class we can calulate alignment by
+// building a class with a single character and a member of the given type.
+template <typename T, bool = std::is_abstract<T>::value>
struct AlignmentCalcImpl {
char x;
+#if defined(_MSC_VER)
+// Disables "structure was padded due to __declspec(align())" warnings that are
+// generated by any class using AlignOf<T> with a manually specified alignment.
+// Although the warning is disabled in the LLVM project we need this pragma
+// as AlignOf.h is a published support header that's available for use
+// out-of-tree, and we would like that to compile cleanly at /W4.
+#pragma warning(suppress : 4324)
+#endif
T t;
private:
AlignmentCalcImpl() {} // Never instantiate.
};
+// Abstract base class helper, this will have the minimal alignment and size
+// for any abstract class. We don't even define its destructor because this
+// type should never be used in a way that requires it.
+struct AlignmentCalcImplBase {
+ virtual ~AlignmentCalcImplBase() = 0;
+};
+
+// When we have an abstract class type, specialize the alignment computation
+// engine to create another abstract class that derives from both an empty
+// abstract base class and the provided type. This has the same effect as the
+// above except that it handles the fact that we can't actually create a member
+// of type T.
+template <typename T>
+struct AlignmentCalcImpl<T, true> : AlignmentCalcImplBase, T {
+ virtual ~AlignmentCalcImpl() = 0;
+};
+
+} // End detail namespace.
+
/// AlignOf - A templated class that contains an enum value representing
/// the alignment of the template argument. For example,
/// AlignOf<int>::Alignment represents the alignment of type "int". The
/// compile-time constant (e.g., for template instantiation).
template <typename T>
struct AlignOf {
- enum { Alignment =
- static_cast<unsigned int>(sizeof(AlignmentCalcImpl<T>) - sizeof(T)) };
-
+#ifndef _MSC_VER
+ // Avoid warnings from GCC like:
+ // comparison between 'enum llvm::AlignOf<X>::<anonymous>' and 'enum
+ // llvm::AlignOf<Y>::<anonymous>' [-Wenum-compare]
+ // by using constexpr instead of enum.
+ // (except on MSVC, since it doesn't support constexpr yet).
+ static constexpr unsigned Alignment = static_cast<unsigned int>(
+ sizeof(detail::AlignmentCalcImpl<T>) - sizeof(T));
+#else
+ enum {
+ Alignment = static_cast<unsigned int>(sizeof(detail::AlignmentCalcImpl<T>) -
+ sizeof(T))
+ };
+#endif
enum { Alignment_GreaterEqual_2Bytes = Alignment >= 2 ? 1 : 0 };
enum { Alignment_GreaterEqual_4Bytes = Alignment >= 4 ? 1 : 0 };
enum { Alignment_GreaterEqual_8Bytes = Alignment >= 8 ? 1 : 0 };
enum { Alignment_LessEqual_4Bytes = Alignment <= 4 ? 1 : 0 };
enum { Alignment_LessEqual_8Bytes = Alignment <= 8 ? 1 : 0 };
enum { Alignment_LessEqual_16Bytes = Alignment <= 16 ? 1 : 0 };
-
};
+#ifndef _MSC_VER
+template <typename T> constexpr unsigned AlignOf<T>::Alignment;
+#endif
+
/// alignOf - A templated function that returns the minimum alignment of
/// of a type. This provides no extra functionality beyond the AlignOf
/// class besides some cosmetic cleanliness. Example usage:
template <typename T>
inline unsigned alignOf() { return AlignOf<T>::Alignment; }
-
+/// \struct AlignedCharArray
/// \brief Helper for building an aligned character array type.
///
/// This template is used to explicitly build up a collection of aligned
-/// character types. We have to build these up using a macro and explicit
+/// character array types. We have to build these up using a macro and explicit
/// specialization to cope with old versions of MSVC and GCC where only an
/// 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;
-};
+
+// MSVC requires special handling here.
+#ifndef _MSC_VER
+
#if __has_feature(cxx_alignas)
+template<std::size_t Alignment, std::size_t Size>
+struct AlignedCharArray {
+ 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 <> struct AlignedCharArrayImpl<x> { \
- typedef char alignas(x) type; \
- }
-#elif defined(__clang__) || defined(__GNUC__)
-#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
- template <> struct AlignedCharArrayImpl<x> { \
- typedef char type __attribute__((aligned(x))); \
- }
-#elif defined(_MSC_VER)
-#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
- template <> struct AlignedCharArrayImpl<x> { \
- typedef __declspec(align(x)) char type; \
- }
+ 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
-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);
-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
+#else // _MSC_VER
-/// \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.
-///
-/// 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
-/// storage suitable to placement new any of these types over. Support for more
-/// 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 {
- class AlignerImpl {
- T1 t1; T2 t2; T3 t3; T4 t4;
+/// \brief Create a type with an aligned char buffer.
+template<std::size_t Alignment, std::size_t Size>
+struct AlignedCharArray;
+
+// 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. Note that we can't
+// even include the declspec with the union that forces the alignment because
+// MSVC warns on the existence of the declspec despite the union member forcing
+// proper alignment.
- AlignerImpl(); // Never defined or instantiated.
+template<std::size_t Size>
+struct AlignedCharArray<1, Size> {
+ union {
+ char aligned;
+ char buffer[Size];
};
- union SizerImpl {
- char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)];
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<2, Size> {
+ union {
+ short aligned;
+ char buffer[Size];
};
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<4, Size> {
+ union {
+ int aligned;
+ char buffer[Size];
+ };
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<8, Size> {
+ union {
+ double aligned;
+ char buffer[Size];
+ };
+};
+
+
+// The rest of these are provided with a __declspec(align(...)) and we simply
+// can't pass them by-value as function arguments on MSVC.
-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;
+#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
+ template<std::size_t Size> \
+ struct AlignedCharArray<x, Size> { \
+ __declspec(align(x)) char buffer[Size]; \
};
+
+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
+
+#endif // _MSC_VER
+
+namespace detail {
+template <typename T1,
+ typename T2 = char, typename T3 = char, typename T4 = char,
+ typename T5 = char, typename T6 = char, typename T7 = char,
+ typename T8 = char, typename T9 = char, typename T10 = char>
+class AlignerImpl {
+ T1 t1; T2 t2; T3 t3; T4 t4; T5 t5; T6 t6; T7 t7; T8 t8; T9 t9; T10 t10;
+
+ AlignerImpl(); // Never defined or instantiated.
};
+template <typename T1,
+ typename T2 = char, typename T3 = char, typename T4 = char,
+ typename T5 = char, typename T6 = char, typename T7 = char,
+ typename T8 = char, typename T9 = char, typename T10 = char>
+union SizerImpl {
+ char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)],
+ arr5[sizeof(T5)], arr6[sizeof(T6)], arr7[sizeof(T7)], arr8[sizeof(T8)],
+ arr9[sizeof(T9)], arr10[sizeof(T10)];
+};
+} // end namespace detail
+
+/// \brief This union template exposes a suitably aligned and sized character
+/// array member which can hold elements of any of up to ten types.
+///
+/// These types may be arrays, structs, or any other types. The goal is to
+/// expose a char array buffer member which can be used as suitable storage for
+/// a placement new of any of these types. Support for more than ten types can
+/// be added at the cost of more boilerplate.
+template <typename T1,
+ typename T2 = char, typename T3 = char, typename T4 = char,
+ typename T5 = char, typename T6 = char, typename T7 = char,
+ typename T8 = char, typename T9 = char, typename T10 = char>
+struct AlignedCharArrayUnion : llvm::AlignedCharArray<
+ AlignOf<detail::AlignerImpl<T1, T2, T3, T4, T5,
+ T6, T7, T8, T9, T10> >::Alignment,
+ sizeof(detail::SizerImpl<T1, T2, T3, T4, T5,
+ T6, T7, T8, T9, T10>)> {
+};
} // end namespace llvm
#endif
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