ENH: Add conversion for 512bit intrin to 256bit intrin

512-bits intrinsics sometimes not exist in some operations. We can
construct the 512-bits intrinsics with two 256-bits intrinsics.
Therfore, NPYV_IMPL_AVX512_FROM_AVX2_PS_1ARG and
NPYV_IMPL_AVX512_FROM_AVX2_PD_1ARG are added. And the error in
npyv512_combine_ps256 has been fixed too.

Author: howjmay

numpy/core/src/common/simd/avx512/utils.h

@@ -26,7 +26,7 @@
     #define npyv512_combine_ps256(A, B) _mm512_insertf32x8(_mm512_castps256_ps512(A), B, 1)
 #else
     #define npyv512_combine_ps256(A, B) \
-        _mm512_castsi512_ps(npyv512_combine_si256(_mm512_castps_si512(A), _mm512_castps_si512(B)))
+        _mm512_castsi512_ps(npyv512_combine_si256(_mm256_castps_si256(A), _mm256_castps_si256(B)))
 #endif
 
 #define NPYV_IMPL_AVX512_FROM_AVX2_1ARG(FN_NAME, INTRIN) \
@@ -39,6 +39,26 @@
         return npyv512_combine_si256(l_a, h_a);          \
     }
 
+#define NPYV_IMPL_AVX512_FROM_AVX2_PS_1ARG(FN_NAME, INTRIN) \
+    NPY_FINLINE __m512 FN_NAME(__m512 a)                    \
+    {                                                       \
+        __m256 l_a  = npyv512_lower_ps256(a);               \
+        __m256 h_a  = npyv512_higher_ps256(a);              \
+        l_a = INTRIN(l_a);                                  \
+        h_a = INTRIN(h_a);                                  \
+        return npyv512_combine_ps256(l_a, h_a);             \
+    }
+
+#define NPYV_IMPL_AVX512_FROM_AVX2_PD_1ARG(FN_NAME, INTRIN) \
+    NPY_FINLINE __m512d FN_NAME(__m512d a)                  \
+    {                                                       \
+        __m256d l_a  = npyv512_lower_pd256(a);              \
+        __m256d h_a  = npyv512_higher_pd256(a);             \
+        l_a = INTRIN(l_a);                                  \
+        h_a = INTRIN(h_a);                                  \
+        return npyv512_combine_pd256(l_a, h_a);             \
+    }
+
 #define NPYV_IMPL_AVX512_FROM_AVX2_2ARG(FN_NAME, INTRIN) \
     NPY_FINLINE __m512i FN_NAME(__m512i a, __m512i b)    \
     {                                                    \