AVX512F double->int64_t cast
diff --git a/Eigen/src/Core/arch/AVX512/TypeCasting.h b/Eigen/src/Core/arch/AVX512/TypeCasting.h
index b16e9f6..e471684 100644
--- a/Eigen/src/Core/arch/AVX512/TypeCasting.h
+++ b/Eigen/src/Core/arch/AVX512/TypeCasting.h
@@ -82,14 +82,34 @@
template <>
EIGEN_STRONG_INLINE Packet8l pcast<Packet8d, Packet8l>(const Packet8d& a) {
-#if defined(EIGEN_VECTORIZE_AVX512DQ) && defined(EIGEN_VECTORIZE_AVS512VL)
+#if defined(EIGEN_VECTORIZE_AVX512DQ) && defined(EIGEN_VECTORIZE_AVX512VL)
return _mm512_cvttpd_epi64(a);
#else
- EIGEN_ALIGN16 double aux[8];
- pstore(aux, a);
- return _mm512_set_epi64(static_cast<int64_t>(aux[7]), static_cast<int64_t>(aux[6]), static_cast<int64_t>(aux[5]),
- static_cast<int64_t>(aux[4]), static_cast<int64_t>(aux[3]), static_cast<int64_t>(aux[2]),
- static_cast<int64_t>(aux[1]), static_cast<int64_t>(aux[0]));
+ constexpr int kTotalBits = sizeof(double) * CHAR_BIT, kMantissaBits = std::numeric_limits<double>::digits - 1,
+ kExponentBits = kTotalBits - kMantissaBits - 1, kBias = (1 << (kExponentBits - 1)) - 1;
+
+ const __m512i cst_one = _mm512_set1_epi64(1);
+ const __m512i cst_total_bits = _mm512_set1_epi64(kTotalBits);
+ const __m512i cst_bias = _mm512_set1_epi64(kBias);
+
+ __m512i a_bits = _mm512_castpd_si512(a);
+ // shift left by 1 to clear the sign bit, and shift right by kMantissaBits + 1 to recover biased exponent
+ __m512i biased_e = _mm512_srli_epi64(_mm512_slli_epi64(a_bits, 1), kMantissaBits + 1);
+ __m512i e = _mm512_sub_epi64(biased_e, cst_bias);
+
+ // shift to the left by kExponentBits + 1 to clear the sign and exponent bits
+ __m512i shifted_mantissa = _mm512_slli_epi64(a_bits, kExponentBits + 1);
+ // shift to the right by kTotalBits - e to convert the significand to an integer
+ __m512i result_significand = _mm512_srlv_epi64(shifted_mantissa, _mm512_sub_epi64(cst_total_bits, e));
+
+ // add the implied bit
+ __m512i result_exponent = _mm512_sllv_epi64(cst_one, e);
+ // e <= 0 is interpreted as a large positive shift (2's complement), which also conveniently results in zero
+ __m512i result = _mm512_add_epi64(result_significand, result_exponent);
+ // handle negative arguments
+ __mmask8 sign_mask = _mm512_cmplt_epi64_mask(a_bits, _mm512_setzero_si512());
+ result = _mm512_mask_sub_epi64(result, sign_mask, _mm512_setzero_si512(), result);
+ return result;
#endif
}
@@ -110,10 +130,10 @@
template <>
EIGEN_STRONG_INLINE Packet8d pcast<Packet8l, Packet8d>(const Packet8l& a) {
-#if defined(EIGEN_VECTORIZE_AVX512DQ) && defined(EIGEN_VECTORIZE_AVS512VL)
+#if defined(EIGEN_VECTORIZE_AVX512DQ) && defined(EIGEN_VECTORIZE_AVX512VL)
return _mm512_cvtepi64_pd(a);
#else
- EIGEN_ALIGN16 int64_t aux[8];
+ EIGEN_ALIGN64 int64_t aux[8];
pstore(aux, a);
return _mm512_set_pd(static_cast<double>(aux[7]), static_cast<double>(aux[6]), static_cast<double>(aux[5]),
static_cast<double>(aux[4]), static_cast<double>(aux[3]), static_cast<double>(aux[2]),
