SIMD: add generator constructors #6347
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Can you please elaborate a bit more on why we need this? |
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@masterleinad Just updated the PR description to provide a bit more on where generator constructors are typically used, but I |
masterleinad
approved these changes
Aug 9, 2023
| KOKKOS_IMPL_HOST_FORCEINLINE_FUNCTION constexpr explicit simd_mask( | ||
| G&& gen) noexcept | ||
| : m_value(_mm256_castsi256_pd(_mm256_setr_epi64x( | ||
| -std::int64_t(gen(std::integral_constant<std::size_t, 0>())), |
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Why is it correct to negate the argument here?
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It's to set all bits in the lane to 1 when the mask is set to true (in this case, to produce 0xFFFFFFFFFFFFFFFFULL). I guess this imposes an underlying assumption that setting the mask to be true is strictly equivalent to setting it to be 1 rather than any non-zero value.
crtrott
approved these changes
Aug 10, 2023
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Related to #5674
This PR adds a generator constructor for all simd types and mask types:
template <class G> simd(G&& gen)Generator constructors for simd allow constructing simd objects using expressions without needing to manually set a value for each vector lane. For internal implementation purpose, generator constructors have been used to implement generic fallback methods for few operators where simd intrinsics aren't adequately provided to implement such operations (i.e. Arithmetic shift right for AVX2 with int64_t).