[llvm] r291503 - Lift the 10-type limit for AlignedCharArrayUnion
Sean Callanan via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 9 15:23:26 PST 2017
Author: spyffe
Date: Mon Jan 9 17:23:25 2017
New Revision: 291503
URL: http://llvm.org/viewvc/llvm-project?rev=291503&view=rev
Log:
Lift the 10-type limit for AlignedCharArrayUnion
This patch uses C++11 parameter packs and constexpr functions
to allow AlignedCharArrayUnion to hold an arbitrary number of
types.
Differential Revision: https://reviews.llvm.org/D28429
Modified:
llvm/trunk/include/llvm/Support/AlignOf.h
llvm/trunk/unittests/Support/AlignOfTest.cpp
Modified: llvm/trunk/include/llvm/Support/AlignOf.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/AlignOf.h?rev=291503&r1=291502&r2=291503&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/AlignOf.h (original)
+++ llvm/trunk/include/llvm/Support/AlignOf.h Mon Jan 9 17:23:25 2017
@@ -102,45 +102,38 @@ LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
#endif // _MSC_VER
+// This code implements the equivalent of std::aligned_union from C++11.
+// That is supported by Visual Studio 2015 and GCC 5.1.
+// Once these are the baselines for LLVM, we can use std::aligned_union instead.
+
namespace detail {
-template <typename T1,
- typename T2 = char, typename T3 = char, typename T4 = char,
- typename T5 = char, typename T6 = char, typename T7 = char,
- typename T8 = char, typename T9 = char, typename T10 = char>
-class AlignerImpl {
- T1 t1; T2 t2; T3 t3; T4 t4; T5 t5; T6 t6; T7 t7; T8 t8; T9 t9; T10 t10;
+template <typename... Ts> class AlignerImpl;
+template <typename T1, typename... Ts>
+class AlignerImpl<T1, Ts...> : AlignerImpl<Ts...> {
+ T1 t;
AlignerImpl() = delete;
};
-template <typename T1,
- typename T2 = char, typename T3 = char, typename T4 = char,
- typename T5 = char, typename T6 = char, typename T7 = char,
- typename T8 = char, typename T9 = char, typename T10 = char>
-union SizerImpl {
- char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)],
- arr5[sizeof(T5)], arr6[sizeof(T6)], arr7[sizeof(T7)], arr8[sizeof(T8)],
- arr9[sizeof(T9)], arr10[sizeof(T10)];
-};
+template <> class AlignerImpl<> { AlignerImpl() = delete; };
+
+template <typename T1> constexpr size_t sizer() { return sizeof(T1); }
+
+template <typename T1, typename T2, typename... Ts> constexpr size_t sizer() {
+ return (sizeof(T1) > sizer<T2, Ts...>()) ? sizeof(T1) : sizer<T2, Ts...>();
+}
} // 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 ten types.
+/// array member which can hold elements of any of a number of types.
///
/// These types may be arrays, structs, or any other types. The goal is to
/// 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 ten types can
-/// be added at the cost of more boilerplate.
-template <typename T1,
- typename T2 = char, typename T3 = char, typename T4 = char,
- typename T5 = char, typename T6 = char, typename T7 = char,
- typename T8 = char, typename T9 = char, typename T10 = char>
-struct AlignedCharArrayUnion : llvm::AlignedCharArray<
- alignof(llvm::detail::AlignerImpl<T1, T2, T3, T4, T5,
- T6, T7, T8, T9, T10>),
- sizeof(::llvm::detail::SizerImpl<T1, T2, T3, T4, T5,
- T6, T7, T8, T9, T10>)> {
-};
+/// a placement new of any of these types.
+template <typename... Ts>
+struct AlignedCharArrayUnion
+ : llvm::AlignedCharArray<alignof(llvm::detail::AlignerImpl<Ts...>),
+ detail::sizer<Ts...>()> {};
} // end namespace llvm
#endif // LLVM_SUPPORT_ALIGNOF_H
Modified: llvm/trunk/unittests/Support/AlignOfTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/AlignOfTest.cpp?rev=291503&r1=291502&r2=291503&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/AlignOfTest.cpp (original)
+++ llvm/trunk/unittests/Support/AlignOfTest.cpp Mon Jan 9 17:23:25 2017
@@ -91,6 +91,24 @@ V8::~V8() {}
template <typename M> struct T { M m; };
+typedef uint8_t t1;
+typedef uint16_t t2;
+typedef uint32_t t3;
+typedef uint64_t t4;
+typedef int8_t t5;
+typedef int16_t t6;
+typedef int32_t t7;
+typedef int64_t t8;
+typedef struct { uint8_t bytes[16]; } t9;
+typedef struct { uint16_t words[16]; } t10;
+typedef struct { uint32_t words[16]; } t11;
+typedef struct { uint64_t words[16]; } t12;
+
+typedef AlignedCharArrayUnion<t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12> U;
+
+static_assert(sizeof(U) == sizeof(uint64_t[16]), "Statically-computed size must be right");
+static_assert(alignof(U) == alignof(uint64_t), "Statically-computed alignment must be right");
+
TEST(AlignOfTest, BasicAlignedArray) {
EXPECT_LE(1u, alignof(AlignedCharArrayUnion<A1>));
EXPECT_LE(2u, alignof(AlignedCharArrayUnion<A2>));
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