Silence Wignored-attributes in user code

Users of Vc shouldn't have to compile with -Wno-ignored-attributes. So
the Vc headers may not produce any unnecessary noise. (GCC 6 produces
tons of warnings - by default - that are irrelevant.)

Disable ignored-attributes in global.h and reset it at the bottom of
vector.h. This should catch almost all uses of Vc. The few remaining
corner cases are not supported anyway and will only lose the
Wignored-attributes warning in their code.

Additionally, use much less attributes by only adding the alignment
attribute on Vector::EntryType when really necessary (i.e. if sizeof(T)
!= alignof(T), which is the case on 32-bit x86 for double).

Ignore the warning in the types.cpp test, where intrinsic types are
compared with std::is_same

Signed-off-by: Matthias Kretz <[email protected]>

CMakeLists.txt

@@ -69,8 +69,6 @@ if(Vc_COMPILER_IS_GCC)
       list(APPEND disabled_targets
          example_scaling_scalar
          )
-   elseif(Vc_GCC_VERSION VERSION_GREATER "5.99")
-      AddCompilerFlag(-Wno-ignored-attributes)
    endif()
 elseif(Vc_COMPILER_IS_MSVC)
    if(MSVC_VERSION LESS 1700)

avx/vector.h

@@ -88,7 +88,7 @@ template <typename T> class Vector<T, VectorAbi::Avx>
 
     Vc_FREE_STORE_OPERATORS_ALIGNED(alignof(VectorType));
 
-    Vc_ALIGNED_TYPEDEF(sizeof(T), T, EntryType);
+    using EntryType = typename Common::ensure_alignment_equals_sizeof<T>::type;
         using value_type = EntryType;
         typedef EntryType VectorEntryType;
         static constexpr size_t Size = sizeof(VectorType) / sizeof(EntryType);

common/types.h

@@ -358,6 +358,19 @@ template <std::size_t Size, typename F> Vc_INTRINSIC void for_all_vector_entries
     unrolled_loop<std::size_t, 0u, Size>(std::forward<F>(f));
 }
 
+/**\internal
+ * The member type `type` is either `T` or `T` with alignment increased to sizeof(T) if
+ * alignof(T) < sizeof(T).
+ */
+template <class T, std::size_t Size = sizeof(T), std::size_t Alignment = alignof(T)>
+struct ensure_alignment_equals_sizeof {
+    Vc_ALIGNED_TYPEDEF(Size, T, type);
+};
+template <class T, std::size_t Size>
+struct ensure_alignment_equals_sizeof<T, Size, Size> {
+    using type = T;
+};
+
 }  // namespace Common
 }  // namespace Vc
 

include/Vc/global.h

@@ -103,6 +103,14 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define Vc_UNSUPPORTED_COMPILER 1
 #endif
 
+#if defined Vc_GCC && Vc_GCC >= 0x60000
+#define Vc_RESET_DIAGNOSTICS _Pragma("GCC diagnostic pop")
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wignored-attributes"
+#else
+#define Vc_RESET_DIAGNOSTICS
+#endif
+
 #if __cplusplus < 201103 && (!defined Vc_MSVC || _MSC_VER < 1900)
 # error "Vc requires support for C++11."
 #elif __cplusplus >= 201402L

include/Vc/vector.h

@@ -283,4 +283,6 @@ namespace std
 } // namespace std
 #endif
 
+Vc_RESET_DIAGNOSTICS
+
 #endif // VC_VECTOR_H_

mic/vector.h

@@ -80,7 +80,7 @@ class Vector<T, VectorAbi::Mic> : public MIC::StoreMixin<MIC::Vector<T>, T>
     Vc_FREE_STORE_OPERATORS_ALIGNED(64);
     typedef typename MIC::VectorTypeHelper<T>::Type VectorType;
     using vector_type = VectorType;
-    Vc_ALIGNED_TYPEDEF(sizeof(T), T, EntryType);
+    using EntryType = typename Common::ensure_alignment_equals_sizeof<T>::type;
     using value_type = EntryType;
     typedef typename MIC::DetermineVectorEntryType<T>::Type VectorEntryType;
     static constexpr size_t Size = sizeof(VectorType) / sizeof(VectorEntryType);

scalar/vector.h

@@ -52,7 +52,7 @@ template <typename T> class Vector<T, VectorAbi::Scalar>
 
     public:
         using abi = VectorAbi::Scalar;
-    Vc_ALIGNED_TYPEDEF(sizeof(T), T, EntryType);
+        using EntryType = typename Common::ensure_alignment_equals_sizeof<T>::type;
         using VectorEntryType = EntryType;
         using value_type = EntryType;
         using VectorType = EntryType;

src/trigonometric.cpp

@@ -290,8 +290,7 @@ Vc::float_v Trigonometric<Vc::Detail::TrigonometricImplementation<
     Vc::CurrentImplementation::current()>>::asin(const Vc::float_v &_x)
 {
     typedef Vc::float_v V;
-    typedef V::EntryType T;
-    typedef Const<T, V::abi> C;
+    typedef Const<float, V::abi> C;
     typedef V::Mask M;
 
     const M &negative = _x < V::Zero();
@@ -358,8 +357,7 @@ Vc::float_v Trigonometric<Vc::Detail::TrigonometricImplementation<
     Vc::CurrentImplementation::current()>>::atan(const Vc::float_v &_x)
 {
     using V = Vc::float_v;
-    typedef V::EntryType T;
-    typedef Const<T, V::abi> C;
+    typedef Const<float, V::abi> C;
     typedef V::Mask M;
     V x = abs(_x);
     const M &gt_tan_3pi_8 = x > C::atanThrsHi();
@@ -416,8 +414,7 @@ Vc::float_v Trigonometric<Vc::Detail::TrigonometricImplementation<
                                                   const Vc::float_v &x)
 {
     using V = Vc::float_v;
-    typedef V::EntryType T;
-    typedef Const<T, V::abi> C;
+    typedef Const<float, V::abi> C;
     typedef V::Mask M;
 
     const M xZero = x == V::Zero();

sse/intrinsics.h

@@ -727,7 +727,7 @@ template <typename T> struct DetermineGatherMask
 template <typename T> struct VectorTraits
 {
     typedef typename VectorTypeHelper<T>::Type VectorType;
-    Vc_ALIGNED_TYPEDEF(sizeof(T), T, EntryType);
+    using EntryType = typename Common::ensure_alignment_equals_sizeof<T>::type;
     static constexpr size_t Size = sizeof(VectorType) / sizeof(EntryType);
     enum Constants { HasVectorDivision = !std::is_integral<T>::value };
     typedef Mask<T> MaskType;

tests/types.cpp

@@ -23,6 +23,10 @@
 
 #include "unittest.h"
 
+#if defined Vc_GCC && Vc_GCC >= 0x60000
+#pragma GCC diagnostic ignored "-Wignored-attributes"
+#endif
+
 #define ALL_TYPES (ALL_VECTORS, SIMD_ARRAYS(32))
 
 TEST_TYPES(V, check_EntryType, ALL_TYPES)