The TargetData is not used for the isPowerOfTwo determination. It has never

[oota-llvm.git] / include / llvm / Support / AlignOf.h

diff --git a/include/llvm/Support/AlignOf.h b/include/llvm/Support/AlignOf.h
index cebfa7982d6d0719c5a792a4e367d05eb33f6e56..d6b0ab8b3750f2a786ec53d7112de40b1b290963 100644 (file)
--- a/include/llvm/Support/AlignOf.h
+++ b/include/llvm/Support/AlignOf.h
@@ -15,6 +15,9 @@
 #ifndef LLVM_SUPPORT_ALIGNOF_H
 #define LLVM_SUPPORT_ALIGNOF_H
 
+#include "llvm/Support/Compiler.h"
+#include <cstddef>
+
 namespace llvm {
 
 template <typename T>
@@ -54,7 +57,114 @@ struct AlignOf {
 ///  class besides some cosmetic cleanliness.  Example usage:
 ///  alignOf<int>() returns the alignment of an int.
 template <typename T>
-static inline unsigned alignOf() { return AlignOf<T>::Alignment; }
+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 alignas(x) aligned; \
+  }
+#elif defined(__GNUC__) || defined(__IBM_ATTRIBUTES)
+#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.
+  llvm::AlignedCharArrayImpl<AlignOf<AlignerImpl>::Alignment> nonce_member;
+};
 
 } // end namespace llvm
 #endif