Add a mechanism to recursively access to half-size packet types

Eigen/src/Core/GenericPacketMath.h

@@ -42,6 +42,8 @@ namespace internal {
 struct default_packet_traits
 {
   enum {
+    HasHalfPacket = 0,
+    
     HasAdd    = 1,
     HasSub    = 1,
     HasMul    = 1,
@@ -71,10 +73,12 @@ struct default_packet_traits
 template<typename T> struct packet_traits : default_packet_traits
 {
   typedef T type;
+  typedef T half;
   enum {
     Vectorizable = 0,
     size = 1,
-    AlignedOnScalar = 0
+    AlignedOnScalar = 0,
+    HasHalfPacket = 0
   };
   enum {
     HasAdd    = 0,

Eigen/src/Core/arch/AVX/Complex.h

@@ -25,10 +25,12 @@ struct Packet4cf
 template<> struct packet_traits<std::complex<float> >  : default_packet_traits
 {
   typedef Packet4cf type;
+  typedef Packet2cf half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size = 4,
+    HasHalfPacket = 1,
 
     HasAdd    = 1,
     HasSub    = 1,
@@ -257,10 +259,12 @@ struct Packet2cd
 template<> struct packet_traits<std::complex<double> >  : default_packet_traits
 {
   typedef Packet2cd type;
+  typedef Packet1cd half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 0,
     size = 2,
+    HasHalfPacket = 1,
 
     HasAdd    = 1,
     HasSub    = 1,

Eigen/src/Core/arch/AVX/PacketMath.h

@@ -40,10 +40,12 @@ template<> struct is_arithmetic<__m256d> { enum { value = true }; };
 template<> struct packet_traits<float>  : default_packet_traits
 {
   typedef Packet8f type;
+  typedef Packet4f half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size=8,
+    HasHalfPacket = 1,
 
     HasDiv  = 1,
     HasSin  = 0,
@@ -56,10 +58,12 @@ template<> struct packet_traits<float>  : default_packet_traits
 template<> struct packet_traits<double> : default_packet_traits
 {
   typedef Packet4d type;
+  typedef Packet2d half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size=4,
+    HasHalfPacket = 1,
 
     HasDiv  = 1,
     HasExp  = 0

Eigen/src/Core/arch/AltiVec/Complex.h

@@ -33,6 +33,7 @@ struct Packet2cf
 template<> struct packet_traits<std::complex<float> >  : default_packet_traits
 {
   typedef Packet2cf type;
+  typedef Packet2cf half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,

Eigen/src/Core/arch/AltiVec/PacketMath.h

@@ -73,6 +73,7 @@ static Packet4f p4f_ZERO_ = (Packet4f) vec_sl((Packet4ui)p4i_MINUS1, (Packet4ui)
 template<> struct packet_traits<float>  : default_packet_traits
 {
   typedef Packet4f type;
+  typedef Packet4f half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
@@ -89,6 +90,7 @@ template<> struct packet_traits<float>  : default_packet_traits
 template<> struct packet_traits<int>    : default_packet_traits
 {
   typedef Packet4i type;
+  typedef Packet4i half;
   enum {
     // FIXME check the Has*
     Vectorizable = 1,

Eigen/src/Core/arch/NEON/Complex.h

@@ -28,6 +28,7 @@ struct Packet2cf
 template<> struct packet_traits<std::complex<float> >  : default_packet_traits
 {
   typedef Packet2cf type;
+  typedef Packet2cf half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,

Eigen/src/Core/arch/NEON/PacketMath.h

@@ -66,6 +66,7 @@ typedef uint32x4_t  Packet4ui;
 template<> struct packet_traits<float>  : default_packet_traits
 {
   typedef Packet4f type;
+  typedef Packet4f half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
@@ -83,6 +84,7 @@ template<> struct packet_traits<float>  : default_packet_traits
 template<> struct packet_traits<int>    : default_packet_traits
 {
   typedef Packet4i type;
+  typedef Packet4i half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,

Eigen/src/Core/arch/SSE/Complex.h

@@ -28,10 +28,12 @@ struct Packet2cf
 template<> struct packet_traits<std::complex<float> >  : default_packet_traits
 {
   typedef Packet2cf type;
+  typedef Packet2cf half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size = 2,
+    HasHalfPacket = 0,
 
     HasAdd    = 1,
     HasSub    = 1,
@@ -276,10 +278,12 @@ struct Packet1cd
 template<> struct packet_traits<std::complex<double> >  : default_packet_traits
 {
   typedef Packet1cd type;
+  typedef Packet1cd half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 0,
     size = 1,
+    HasHalfPacket = 0,
 
     HasAdd    = 1,
     HasSub    = 1,

Eigen/src/Core/arch/SSE/PacketMath.h

@@ -64,10 +64,12 @@ template<> struct is_arithmetic<__m128d> { enum { value = true }; };
 template<> struct packet_traits<float>  : default_packet_traits
 {
   typedef Packet4f type;
+  typedef Packet4f half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size=4,
+    HasHalfPacket = 0,
 
     HasDiv  = 1,
     HasSin  = EIGEN_FAST_MATH,
@@ -80,10 +82,12 @@ template<> struct packet_traits<float>  : default_packet_traits
 template<> struct packet_traits<double> : default_packet_traits
 {
   typedef Packet2d type;
+  typedef Packet2d half;
   enum {
     Vectorizable = 1,
     AlignedOnScalar = 1,
     size=2,
+    HasHalfPacket = 0,
 
     HasDiv  = 1,
     HasExp  = 1,
@@ -94,6 +98,7 @@ template<> struct packet_traits<double> : default_packet_traits
 template<> struct packet_traits<int>    : default_packet_traits
 {
   typedef Packet4i type;
+  typedef Packet4i half;
   enum {
     // FIXME check the Has*
     Vectorizable = 1,