Fix conversion of `Eigen::half` to `_Float16` in AVX512 code
diff --git a/Eigen/src/Core/arch/AVX512/PacketMathFP16.h b/Eigen/src/Core/arch/AVX512/PacketMathFP16.h
index d4a5816..93ae95b 100644
--- a/Eigen/src/Core/arch/AVX512/PacketMathFP16.h
+++ b/Eigen/src/Core/arch/AVX512/PacketMathFP16.h
@@ -109,7 +109,13 @@
 

 template <>

 EIGEN_STRONG_INLINE Packet32h pset1<Packet32h>(const Eigen::half& from) {

-  return _mm512_set1_ph(static_cast<_Float16>(from));

+  // half/half_raw is bit compatible

+  return _mm512_set1_ph(numext::bit_cast<_Float16>(from));

+}

+

+template <>

+EIGEN_STRONG_INLINE Packet32h pzero(const Packet32h& /*a*/) {

+  return _mm512_setzero_ph();

 }

 

 // pset1frombits

@@ -209,10 +215,8 @@
 // plset

 template <>

 EIGEN_STRONG_INLINE Packet32h plset<Packet32h>(const half& a) {

-  return _mm512_add_ph(_mm512_set1_ph(a),

-                       _mm512_set_ph(31.0f, 30.0f, 29.0f, 28.0f, 27.0f, 26.0f, 25.0f, 24.0f, 23.0f, 22.0f, 21.0f, 20.0f,

-                                     19.0f, 18.0f, 17.0f, 16.0f, 15.0f, 14.0f, 13.0f, 12.0f, 11.0f, 10.0f, 9.0f, 8.0f,

-                                     7.0f, 6.0f, 5.0f, 4.0f, 3.0f, 2.0f, 1.0f, 0.0f));

+  return _mm512_add_ph(pset1<Packet32h>(a), _mm512_set_ph(31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17,

+                                                          16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0));

 }

 

 // por

@@ -510,7 +514,7 @@
 

 template <>

 EIGEN_STRONG_INLINE Packet32h pnegate<Packet32h>(const Packet32h& a) {

-  return _mm512_sub_ph(_mm512_set1_ph(0.0), a);

+  return psub(pzero(a), a);

 }

 

 // pconj