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authorMichael J. Spencer <bigcheesegs@gmail.com>2012-12-31 19:54:45 +0000
committerMichael J. Spencer <bigcheesegs@gmail.com>2012-12-31 19:54:45 +0000
commit3c6f89aa2e489b79f16270dae42d10059234cf82 (patch)
tree0e645e0c6803e47b09fb35a8f929c4178217884b
parent44365353a415d37daae9df53fbf6a91677ed90d3 (diff)
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[AlignOf] Add AlignedCharArray and refactor AlignedCharArrayUnion.
This adds AlignedCharArray<Alignment, Size>. A templated struct that contains a member named buffer of type char[Size] that is aligned to Alignment. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171319 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--include/llvm/Support/AlignOf.h168
-rw-r--r--unittests/Support/AlignOfTest.cpp13
2 files changed, 107 insertions, 74 deletions
diff --git a/include/llvm/Support/AlignOf.h b/include/llvm/Support/AlignOf.h
index d6b0ab8..f8e2cfa 100644
--- a/include/llvm/Support/AlignOf.h
+++ b/include/llvm/Support/AlignOf.h
@@ -19,7 +19,6 @@
#include <cstddef>
namespace llvm {
-
template <typename T>
struct AlignmentCalcImpl {
char x;
@@ -49,7 +48,6 @@ struct AlignOf {
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
@@ -59,112 +57,138 @@ struct AlignOf {
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;
// 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; \
- }
+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> { \
- char aligned __attribute__((aligned(x))); \
- }
-#else
-# error No supported align as directive.
-#endif
+ 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);
-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);
+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
+
#else // _MSC_VER
+/// \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.
-template <> struct AlignedCharArrayImpl<1> { char aligned; };
-template <> struct AlignedCharArrayImpl<2> { short aligned; };
-template <> struct AlignedCharArrayImpl<4> { int aligned; };
-template <> struct AlignedCharArrayImpl<8> { double aligned; };
+
+template<std::size_t Size>
+struct AlignedCharArray<1, Size> {
+ union {
+ char aligned;
+ __declspec(align(1)) char buffer[Size];
+ };
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<2, Size> {
+ union {
+ short aligned;
+ __declspec(align(2)) char buffer[Size];
+ };
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<4, Size> {
+ union {
+ int aligned;
+ __declspec(align(4)) char buffer[Size];
+ };
+};
+
+template<std::size_t Size>
+struct AlignedCharArray<8, Size> {
+ union {
+ double aligned;
+ __declspec(align(8)) char buffer[Size];
+ };
+};
#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.
+ 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>
+class AlignerImpl {
+ T1 t1; T2 t2; T3 t3; T4 t4;
+
+ AlignerImpl(); // Never defined or instantiated.
+};
+
+template <typename T1,
+ typename T2 = char, typename T3 = char, typename T4 = char>
+union SizerImpl {
+ char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)];
+};
+} // 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 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.
+/// 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 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;
+struct AlignedCharArrayUnion :
+ llvm::AlignedCharArray<AlignOf<detail::AlignerImpl<T1, T2, T3, T4> >
+ ::Alignment,
+ sizeof(detail::SizerImpl<T1, T2, T3, T4>)> {
};
-
} // end namespace llvm
#endif
diff --git a/unittests/Support/AlignOfTest.cpp b/unittests/Support/AlignOfTest.cpp
index b518f3b..40f7295 100644
--- a/unittests/Support/AlignOfTest.cpp
+++ b/unittests/Support/AlignOfTest.cpp
@@ -14,7 +14,6 @@
using namespace llvm;
namespace {
-
// Disable warnings about questionable type definitions.
// We're testing that even questionable types work with the alignment utilities.
#ifdef _MSC_VER
@@ -321,6 +320,16 @@ TEST(AlignOfTest, BasicAlignedArray) {
#ifndef _MSC_VER
EXPECT_EQ(sizeof(V8), sizeof(AlignedCharArrayUnion<V8>));
#endif
-}
+ EXPECT_EQ(1u, (alignOf<AlignedCharArray<1, 1> >()));
+ EXPECT_EQ(2u, (alignOf<AlignedCharArray<2, 1> >()));
+ EXPECT_EQ(4u, (alignOf<AlignedCharArray<4, 1> >()));
+ EXPECT_EQ(8u, (alignOf<AlignedCharArray<8, 1> >()));
+ EXPECT_EQ(16u, (alignOf<AlignedCharArray<16, 1> >()));
+
+ EXPECT_EQ(1u, sizeof(AlignedCharArray<1, 1>));
+ EXPECT_EQ(7u, sizeof(AlignedCharArray<1, 7>));
+ EXPECT_EQ(2u, sizeof(AlignedCharArray<2, 2>));
+ EXPECT_EQ(16u, sizeof(AlignedCharArray<2, 16>));
+}
}