Added llvm::AlignOf, a template class whose purpose is to portably

compute the minimum memory alignment of arbitrary types.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43086 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/AlignOf.h

@@ -0,0 +1,43 @@
+//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Ted Kremenek and 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_ALIGNOF_H
+#define LLVM_SUPPORT_ALIGNOF_H
+
+#include <cassert>
+
+namespace llvm {
+  
+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 = sizeof(AlignmentCalcImpl<T>) - sizeof(T) };
+};
+  
+} // end namespace llvm
+#endif