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61 lines
2.2 KiB
C++
61 lines
2.2 KiB
C++
//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the AlignOf function that computes alignments for
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// arbitrary types.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_ALIGNOF_H
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#define LLVM_SUPPORT_ALIGNOF_H
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namespace llvm {
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template <typename T>
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struct AlignmentCalcImpl {
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char x;
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T t;
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private:
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AlignmentCalcImpl() {} // Never instantiate.
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};
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/// AlignOf - A templated class that contains an enum value representing
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/// the alignment of the template argument. For example,
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/// AlignOf<int>::Alignment represents the alignment of type "int". The
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/// alignment calculated is the minimum alignment, and not necessarily
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/// the "desired" alignment returned by GCC's __alignof__ (for example). Note
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/// that because the alignment is an enum value, it can be used as a
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/// compile-time constant (e.g., for template instantiation).
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template <typename T>
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struct AlignOf {
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enum { Alignment =
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static_cast<unsigned int>(sizeof(AlignmentCalcImpl<T>) - sizeof(T)) };
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enum { Alignment_GreaterEqual_2Bytes = Alignment >= 2 ? 1 : 0 };
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enum { Alignment_GreaterEqual_4Bytes = Alignment >= 4 ? 1 : 0 };
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enum { Alignment_GreaterEqual_8Bytes = Alignment >= 8 ? 1 : 0 };
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enum { Alignment_GreaterEqual_16Bytes = Alignment >= 16 ? 1 : 0 };
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enum { Alignment_LessEqual_2Bytes = Alignment <= 2 ? 1 : 0 };
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enum { Alignment_LessEqual_4Bytes = Alignment <= 4 ? 1 : 0 };
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enum { Alignment_LessEqual_8Bytes = Alignment <= 8 ? 1 : 0 };
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enum { Alignment_LessEqual_16Bytes = Alignment <= 16 ? 1 : 0 };
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};
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/// alignof - A templated function that returns the mininum alignment of
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/// of a type. This provides no extra functionality beyond the AlignOf
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/// class besides some cosmetic cleanliness. Example usage:
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/// alignof<int>() returns the alignment of an int.
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template <typename T>
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static inline unsigned alignof() { return AlignOf<T>::Alignment; }
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} // end namespace llvm
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#endif
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