--- /dev/null
+//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the AlignOf function that computes alignments for
+// arbitrary types.
+//
+//===----------------------------------------------------------------------===//
+
+// Taken from llvmCore-3425.0.31.
+
+#ifndef LLVM_SUPPORT_ALIGNOF_H
+#define LLVM_SUPPORT_ALIGNOF_H
+
+#include <cstddef>
+
+namespace objc {
+
+template <typename T>
+struct AlignmentCalcImpl {
+ char x;
+ T t;
+private:
+ AlignmentCalcImpl() {} // Never instantiate.
+};
+
+/// 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
+/// alignment calculated is the minimum alignment, and not necessarily
+/// the "desired" alignment returned by GCC's __alignof__ (for example). Note
+/// that because the alignment is an enum value, it can be used as a
+/// compile-time constant (e.g., for template instantiation).
+template <typename T>
+struct AlignOf {
+ enum { Alignment =
+ static_cast<unsigned int>(sizeof(AlignmentCalcImpl<T>) - sizeof(T)) };
+
+ 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_GreaterEqual_16Bytes = Alignment >= 16 ? 1 : 0 };
+
+ enum { Alignment_LessEqual_2Bytes = Alignment <= 2 ? 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 };
+
+};
+
+/// 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:
+/// alignOf<int>() returns the alignment of an int.
+template <typename T>
+inline unsigned alignOf() { return AlignOf<T>::Alignment; }
+
+
+/// \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
+/// 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;
+
+// MSVC requires special handling here.
+#ifndef _MSC_VER
+
+#if __has_feature(cxx_alignas)
+#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
+ template <> struct AlignedCharArrayImpl<x> { \
+ char aligned alignas(x); \
+ }
+#elif defined(__GNUC__)
+#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
+ template <> struct AlignedCharArrayImpl<x> { \
+ char aligned __attribute__((aligned(x))); \
+ }
+#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);
+
+#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
+
+#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
+/// 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>
+union AlignedCharArrayUnion {
+private:
+ class AlignerImpl {
+ T1 t1; T2 t2; T3 t3; T4 t4;
+
+ AlignerImpl(); // Never defined or instantiated.
+ };
+ union SizerImpl {
+ char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)];
+ };
+
+public:
+ /// \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.
+ AlignedCharArrayImpl<AlignOf<AlignerImpl>::Alignment> nonce_member;
+};
+
+} // end namespace objc
+#endif
projects / apple / objc4.git / blobdiff