Vc-1.2.0 does not work with Intel C/C++ compiler 17.0.0

[amadio]

I cannot compile any code using Vc with the Intel C/C++ compiler 17.0.0. Please see below for details:

antares ~ $ icc --version
icc (ICC) 17.0.0 20160721
Copyright (C) 1985-2016 Intel Corporation.  All rights reserved.

antares ~ $ cat test.cc
#include <Vc/Vc>

int main()
{
  return 0;
}
antares ~ $ icc -Wall -std=c++11 -march=native -o test test.cc 
In file included from /usr/include/Vc/vector.h(192),
                 from /usr/include/Vc/Vc(31),
                 from test.cc(1):
/usr/include/Vc/common/simdarray.h(506): error: bad attribute argument substitution
  class alignas(((Common::nextPowerOfTwo(N) * (sizeof(V) / V::size()) - 1) & 127) +
                ^
          detected during:
            instantiation of class "Vc_1::SimdArray<T, N, V, Wt> [with T=unsigned short, N=32UL, V=Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, Wt=16UL]" at line 108 of "/usr/include/Vc/scalar/../common/../traits/type_traits.h"
            instantiation of class "Vc_1::Traits::vector_size_internal<T, true> [with T=Vc_1::Traits::decay<Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>>]" at line 172 of "/usr/include/Vc/scalar/../common/../traits/type_traits.h"
            instantiation of class "Vc_1::Traits::simd_vector_size<T> [with T=Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>]" at line 1357
            processing of template argument list for "Vc_1::result_vector_type_internal::evaluate" based on template arguments <short, Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>> at line 1411
            instantiation of type "Vc_1::result_vector_type<short, Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>>" at line 1414

In file included from /usr/include/Vc/vector.h(192),
                 from /usr/include/Vc/Vc(31),
                 from test.cc(1):
/usr/include/Vc/common/simdarray.h(83): error: bad attribute argument substitution
      ((Common::nextPowerOfTwo(N) * (sizeof(VectorType_) / VectorType_::size()) - 1) & 127) +
      ^
          detected during:
            instantiation of class "Vc_1::SimdArray<T, N, VectorType_, N> [with T=unsigned short, N=16UL, VectorType_=Vc_1::Common::select_best_vector_type<unsigned short, 16UL>]" at line 532
            instantiation of class "Vc_1::SimdArray<T, N, V, Wt> [with T=unsigned short, N=32UL, V=Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, Wt=16UL]" at line 108 of "/usr/include/Vc/scalar/../common/../traits/type_traits.h"
            instantiation of class "Vc_1::Traits::vector_size_internal<T, true> [with T=Vc_1::Traits::decay<Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>>]" at line 172 of "/usr/include/Vc/scalar/../common/../traits/type_traits.h"
            instantiation of class "Vc_1::Traits::simd_vector_size<T> [with T=Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>]" at line 1357
            processing of template argument list for "Vc_1::result_vector_type_internal::evaluate" based on template arguments <short, Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>> at line 1411
            instantiation of type "Vc_1::result_vector_type<short, Vc_1::SimdArray<unsigned short, 32UL, Vc_1::Common::select_best_vector_type<unsigned short, 32UL>, 16UL>>" at line 1414

In file included from /usr/include/Vc/vector.h(229),
                 from /usr/include/Vc/Vc(31),
                 from test.cc(1):
/usr/include/Vc/common/simdmaskarray.h(56): error: bad attribute argument substitution
      ((Common::nextPowerOfTwo(N) * (sizeof(VectorType_) / VectorType_::size()) - 1) & 127) +
      ^
          detected during instantiation of class "Vc_1::SimdMaskArray<T, N, VectorType_, N> [with T=int, N=4UL, VectorType_=Vc_1::SSE::int_v]" at line 85 of "/usr/include/Vc/sse/math.h"

In file included from /usr/include/Vc/vector.h(234),
                 from /usr/include/Vc/Vc(31),
                 from test.cc(1):
/usr/include/Vc/common/simdmaskarray.h(285): error: bad attribute argument substitution
  class alignas(((Common::nextPowerOfTwo(N) * (sizeof(V) / V::size()) - 1) & 127) +
                ^
          detected during instantiation of class "Vc_1::SimdMaskArray<T, N, V, Wt> [with T=int, N=8UL, V=Vc_1::SSE::int_v, Wt=4UL]" at line 225 of "/usr/include/Vc/avx/math.h"

compilation aborted for test.cc (code 2)

[mattkretz]

Yes, that's a bug in ICC. I have a workaround in current master of Vc. I'm working on finalizing Vc 1.3 so that you can have the fix in a release.

[amadio]

Thank you. If you are going to make a new release, though, I recommend checking the KNC build too. I've had problems with Vc on KNC even with ICC 16. Best,

[mattkretz]

yes, thanks. I think I also fixed those. At least my nightlies for master have been looking good.

[noma]

Exactly that bug was reported to Intel in May. :-/ Glad to read you've worked around it, and Vc can be used with the Intel Compiler again.

[mattkretz]

Thanks for the heads up. Good that Intel has this bug on its plate. (I seriously sometimes wonder about their QA. ICC has way more regressions than any other compiler I work with.)

In case you need it: The workaround required moving the alignas from the class declaration down to the first data member of the class.