intrin: fixed int64->double conversion for AVX-512

modules/core/include/opencv2/core/hal/intrin_avx512.hpp

@@ -1553,13 +1553,13 @@ inline v_float64x8 v_cvt_f64(const v_int64x8& v)
  return v_float64x8(_mm512_cvtepi64_pd(v.val));
 #else
  // constants encoded as floating-point
- __m512i magic_i_lo = _mm512_set1_epi64x(0x4330000000000000); // 2^52
- __m512i magic_i_hi32 = _mm512_set1_epi64x(0x4530000080000000); // 2^84 + 2^63
- __m512i magic_i_all = _mm512_set1_epi64x(0x4530000080100000); // 2^84 + 2^63 + 2^52
+ __m512i magic_i_lo = _mm512_set1_epi64(0x4330000000000000); // 2^52
+ __m512i magic_i_hi32 = _mm512_set1_epi64(0x4530000080000000); // 2^84 + 2^63
+ __m512i magic_i_all = _mm512_set1_epi64(0x4530000080100000); // 2^84 + 2^63 + 2^52
  __m512d magic_d_all = _mm512_castsi512_pd(magic_i_all);
 
  // Blend the 32 lowest significant bits of v with magic_int_lo
- __m512i v_lo = _mm512_blend_epi32(magic_i_lo, v.val, 0x55);
+ __m512i v_lo = _mm512_mask_blend_epi32(0x5555, magic_i_lo, v.val);
  // Extract the 32 most significant bits of v
  __m512i v_hi = _mm512_srli_epi64(v.val, 32);
  // Flip the msb of v_hi and blend with 0x45300000