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

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008 Konstantinos Margaritis <markos@codex.gr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_PACKET_MATH_ALTIVEC_H
#define EIGEN_PACKET_MATH_ALTIVEC_H

namespace Eigen {

namespace internal {

#ifndef EIGEN_CACHEFRIENDLY_PRODUCT_THRESHOLD
#define EIGEN_CACHEFRIENDLY_PRODUCT_THRESHOLD 4
#endif

#ifndef EIGEN_HAS_SINGLE_INSTRUCTION_MADD
#define EIGEN_HAS_SINGLE_INSTRUCTION_MADD
#endif

#ifndef EIGEN_HAS_SINGLE_INSTRUCTION_CJMADD
#define EIGEN_HAS_SINGLE_INSTRUCTION_CJMADD
#endif

// NOTE Altivec has 32 registers, but Eigen only accepts a value of 8 or 16
#ifndef EIGEN_ARCH_DEFAULT_NUMBER_OF_REGISTERS
#define EIGEN_ARCH_DEFAULT_NUMBER_OF_REGISTERS  32
#endif

typedef __vector float          Packet4f;
typedef __vector int            Packet4i;
typedef __vector unsigned int   Packet4ui;
typedef __vector __bool int     Packet4bi;
typedef __vector short int      Packet8i;
typedef __vector unsigned char  Packet16uc;

// We don't want to write the same code all the time, but we need to reuse the constants
// and it doesn't really work to declare them global, so we define macros instead

#define _EIGEN_DECLARE_CONST_FAST_Packet4f(NAME,X) \
  Packet4f p4f_##NAME = (Packet4f) vec_splat_s32(X)

#define _EIGEN_DECLARE_CONST_FAST_Packet4i(NAME,X) \
  Packet4i p4i_##NAME = vec_splat_s32(X)

#define _EIGEN_DECLARE_CONST_Packet4f(NAME,X) \
  Packet4f p4f_##NAME = pset1<Packet4f>(X)

#define _EIGEN_DECLARE_CONST_Packet4i(NAME,X) \
  Packet4i p4i_##NAME = pset1<Packet4i>(X)

#define _EIGEN_DECLARE_CONST_Packet2d(NAME,X) \
  Packet2d p2d_##NAME = pset1<Packet2d>(X)

#define _EIGEN_DECLARE_CONST_Packet2l(NAME,X) \
  Packet2l p2l_##NAME = pset1<Packet2l>(X)

#define _EIGEN_DECLARE_CONST_Packet4f_FROM_INT(NAME,X) \
  const Packet4f p4f_##NAME = reinterpret_cast<Packet4f>(pset1<Packet4i>(X))

#define DST_CHAN 1
#define DST_CTRL(size, count, stride) (((size) << 24) | ((count) << 16) | (stride))

// These constants are endian-agnostic
static _EIGEN_DECLARE_CONST_FAST_Packet4f(ZERO, 0);
static _EIGEN_DECLARE_CONST_FAST_Packet4i(ZERO, 0);
#ifndef __VSX__
static _EIGEN_DECLARE_CONST_FAST_Packet4i(ONE,1);
static Packet4f p4f_ONE = vec_ctf(p4i_ONE, 0);
#endif
static _EIGEN_DECLARE_CONST_FAST_Packet4i(MINUS16,-16);
static _EIGEN_DECLARE_CONST_FAST_Packet4i(MINUS1,-1);
static Packet4f p4f_ZERO_ = (Packet4f) vec_sl((Packet4ui)p4i_MINUS1, (Packet4ui)p4i_MINUS1);

static Packet4f p4f_COUNTDOWN = { 0.0, 1.0, 2.0, 3.0 };
static Packet4i p4i_COUNTDOWN = { 0, 1, 2, 3 };

static Packet16uc p16uc_REVERSE32 = { 12,13,14,15, 8,9,10,11, 4,5,6,7, 0,1,2,3 };
static Packet16uc p16uc_DUPLICATE32_HI = { 0,1,2,3, 0,1,2,3, 4,5,6,7, 4,5,6,7 };

// Mask alignment
#ifdef __PPC64__
#define _EIGEN_MASK_ALIGNMENT	0xfffffffffffffff0
#else
#define _EIGEN_MASK_ALIGNMENT	0xfffffff0
#endif

#define _EIGEN_ALIGNED_PTR(x)	((ptrdiff_t)(x) & _EIGEN_MASK_ALIGNMENT)

// Handle endianness properly while loading constants
// Define global static constants:
#ifdef _BIG_ENDIAN
static Packet16uc p16uc_FORWARD = vec_lvsl(0, (float*)0); 
static Packet16uc p16uc_REVERSE64 = { 8,9,10,11, 12,13,14,15, 0,1,2,3, 4,5,6,7 };
static Packet16uc p16uc_PSET32_WODD   = vec_sld((Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 0), (Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 2), 8);//{ 0,1,2,3, 0,1,2,3, 8,9,10,11, 8,9,10,11 };
static Packet16uc p16uc_PSET32_WEVEN  = vec_sld(p16uc_DUPLICATE32_HI, (Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 3), 8);//{ 4,5,6,7, 4,5,6,7, 12,13,14,15, 12,13,14,15 };
static Packet16uc p16uc_HALF64_0_16 = vec_sld((Packet16uc)p4i_ZERO, vec_splat((Packet16uc) vec_abs(p4i_MINUS16), 3), 8);      //{ 0,0,0,0, 0,0,0,0, 16,16,16,16, 16,16,16,16};
#else
static Packet16uc p16uc_FORWARD = p16uc_REVERSE32; 
static Packet16uc p16uc_REVERSE64 = { 8,9,10,11, 12,13,14,15, 0,1,2,3, 4,5,6,7 };
static Packet16uc p16uc_PSET32_WODD = vec_sld((Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 1), (Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 3), 8);//{ 0,1,2,3, 0,1,2,3, 8,9,10,11, 8,9,10,11 };
static Packet16uc p16uc_PSET32_WEVEN = vec_sld((Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 0), (Packet16uc) vec_splat((Packet4ui)p16uc_FORWARD, 2), 8);//{ 4,5,6,7, 4,5,6,7, 12,13,14,15, 12,13,14,15 };
static Packet16uc p16uc_HALF64_0_16 = vec_sld(vec_splat((Packet16uc) vec_abs(p4i_MINUS16), 0), (Packet16uc)p4i_ZERO, 8);      //{ 0,0,0,0, 0,0,0,0, 16,16,16,16, 16,16,16,16};
#endif // _BIG_ENDIAN

static Packet16uc p16uc_PSET64_HI = (Packet16uc) vec_mergeh((Packet4ui)p16uc_PSET32_WODD, (Packet4ui)p16uc_PSET32_WEVEN);     //{ 0,1,2,3, 4,5,6,7, 0,1,2,3, 4,5,6,7 };
static Packet16uc p16uc_PSET64_LO = (Packet16uc) vec_mergel((Packet4ui)p16uc_PSET32_WODD, (Packet4ui)p16uc_PSET32_WEVEN);     //{ 8,9,10,11, 12,13,14,15, 8,9,10,11, 12,13,14,15 };
static Packet16uc p16uc_TRANSPOSE64_HI = vec_add(p16uc_PSET64_HI, p16uc_HALF64_0_16);                                         //{ 0,1,2,3, 4,5,6,7, 16,17,18,19, 20,21,22,23};
static Packet16uc p16uc_TRANSPOSE64_LO = vec_add(p16uc_PSET64_LO, p16uc_HALF64_0_16);                                         //{ 8,9,10,11, 12,13,14,15, 24,25,26,27, 28,29,30,31};

static Packet16uc p16uc_COMPLEX32_REV = vec_sld(p16uc_REVERSE32, p16uc_REVERSE32, 8);                                         //{ 4,5,6,7, 0,1,2,3, 12,13,14,15, 8,9,10,11 };

#ifdef _BIG_ENDIAN
static Packet16uc p16uc_COMPLEX32_REV2 = vec_sld(p16uc_FORWARD, p16uc_FORWARD, 8);                                            //{ 8,9,10,11, 12,13,14,15, 0,1,2,3, 4,5,6,7 };
#else
static Packet16uc p16uc_COMPLEX32_REV2 = vec_sld(p16uc_PSET64_HI, p16uc_PSET64_LO, 8);                                            //{ 8,9,10,11, 12,13,14,15, 0,1,2,3, 4,5,6,7 };
#endif // _BIG_ENDIAN

template<> struct packet_traits<float>  : default_packet_traits
{
  typedef Packet4f type;
  typedef Packet4f half;
  enum {
    Vectorizable = 1,
    AlignedOnScalar = 1,
    size=4,

    // FIXME check the Has*
#if defined(__VSX__)
    HasDiv  = 1,
#endif
    HasSin  = 0,
    HasCos  = 0,
    HasLog  = 1,
    HasExp  = 1,
    HasSqrt = 0
  };
};
template<> struct packet_traits<int>    : default_packet_traits
{
  typedef Packet4i type;
  typedef Packet4i half;
  enum {
    // FIXME check the Has*
    Vectorizable = 1,
    AlignedOnScalar = 1,
    size=4
  };
};


template<> struct unpacket_traits<Packet4f> { typedef float  type; enum {size=4}; typedef Packet4f half; };
template<> struct unpacket_traits<Packet4i> { typedef int    type; enum {size=4}; typedef Packet4i half; };

inline std::ostream & operator <<(std::ostream & s, const Packet16uc & v)
{
  union {
    Packet16uc   v;
    unsigned char n[16];
  } vt;
  vt.v = v;
  for (int i=0; i< 16; i++)
    s << (int)vt.n[i] << ", ";
  return s;
}

inline std::ostream & operator <<(std::ostream & s, const Packet4f & v)
{
  union {
    Packet4f   v;
    float n[4];
  } vt;
  vt.v = v;
  s << vt.n[0] << ", " << vt.n[1] << ", " << vt.n[2] << ", " << vt.n[3];
  return s;
}

inline std::ostream & operator <<(std::ostream & s, const Packet4i & v)
{
  union {
    Packet4i   v;
    int n[4];
  } vt;
  vt.v = v;
  s << vt.n[0] << ", " << vt.n[1] << ", " << vt.n[2] << ", " << vt.n[3];
  return s;
}

inline std::ostream & operator <<(std::ostream & s, const Packet4ui & v)
{
  union {
    Packet4ui   v;
    unsigned int n[4];
  } vt;
  vt.v = v;
  s << vt.n[0] << ", " << vt.n[1] << ", " << vt.n[2] << ", " << vt.n[3];
  return s;
}
/*
inline std::ostream & operator <<(std::ostream & s, const Packetbi & v)
{
  union {
    Packet4bi v;
    unsigned int n[4];
  } vt;
  vt.v = v;
  s << vt.n[0] << ", " << vt.n[1] << ", " << vt.n[2] << ", " << vt.n[3];
  return s;
}*/


// Need to define them first or we get specialization after instantiation errors
template<> EIGEN_STRONG_INLINE Packet4f pload<Packet4f>(const float* from) { EIGEN_DEBUG_ALIGNED_LOAD return vec_ld(0, from); }
template<> EIGEN_STRONG_INLINE Packet4i pload<Packet4i>(const int*     from) { EIGEN_DEBUG_ALIGNED_LOAD return vec_ld(0, from); }

template<> EIGEN_STRONG_INLINE void pstore<float>(float*   to, const Packet4f& from) { EIGEN_DEBUG_ALIGNED_STORE vec_st(from, 0, to); }
template<> EIGEN_STRONG_INLINE void pstore<int>(int*       to, const Packet4i& from) { EIGEN_DEBUG_ALIGNED_STORE vec_st(from, 0, to); }

template<> EIGEN_STRONG_INLINE Packet4f pset1<Packet4f>(const float&  from) {
  // Taken from http://developer.apple.com/hardwaredrivers/ve/alignment.html
  float EIGEN_ALIGN16 af[4];
  af[0] = from;
  Packet4f vc = pload<Packet4f>(af);
  vc = vec_splat(vc, 0);
  return vc;
}

template<> EIGEN_STRONG_INLINE Packet4i pset1<Packet4i>(const int&    from)   {
  int EIGEN_ALIGN16 ai[4];
  ai[0] = from;
  Packet4i vc = pload<Packet4i>(ai);
  vc = vec_splat(vc, 0);
  return vc;
}
template<> EIGEN_STRONG_INLINE void
pbroadcast4<Packet4f>(const float *a,
                      Packet4f& a0, Packet4f& a1, Packet4f& a2, Packet4f& a3)
{
  a3 = pload<Packet4f>(a);
  a0 = vec_splat(a3, 0);
  a1 = vec_splat(a3, 1);
  a2 = vec_splat(a3, 2);
  a3 = vec_splat(a3, 3);
}
template<> EIGEN_STRONG_INLINE void
pbroadcast4<Packet4i>(const int *a,
                      Packet4i& a0, Packet4i& a1, Packet4i& a2, Packet4i& a3)
{
  a3 = pload<Packet4i>(a);
  a0 = vec_splat(a3, 0);
  a1 = vec_splat(a3, 1);
  a2 = vec_splat(a3, 2);
  a3 = vec_splat(a3, 3);
}

template<> EIGEN_DEVICE_FUNC inline Packet4f pgather<float, Packet4f>(const float* from, int stride)
{
  float EIGEN_ALIGN16 af[4];
  af[0] = from[0*stride];
  af[1] = from[1*stride];
  af[2] = from[2*stride];
  af[3] = from[3*stride];
 return pload<Packet4f>(af);
}
template<> EIGEN_DEVICE_FUNC inline Packet4i pgather<int, Packet4i>(const int* from, int stride)
{
  int EIGEN_ALIGN16 ai[4];
  ai[0] = from[0*stride];
  ai[1] = from[1*stride];
  ai[2] = from[2*stride];
  ai[3] = from[3*stride];
 return pload<Packet4i>(ai);
}
template<> EIGEN_DEVICE_FUNC inline void pscatter<float, Packet4f>(float* to, const Packet4f& from, int stride)
{
  float EIGEN_ALIGN16 af[4];
  pstore<float>(af, from);
  to[0*stride] = af[0];
  to[1*stride] = af[1];
  to[2*stride] = af[2];
  to[3*stride] = af[3];
}
template<> EIGEN_DEVICE_FUNC inline void pscatter<int, Packet4i>(int* to, const Packet4i& from, int stride)
{
  int EIGEN_ALIGN16 ai[4];
  pstore<int>((int *)ai, from);
  to[0*stride] = ai[0];
  to[1*stride] = ai[1];
  to[2*stride] = ai[2];
  to[3*stride] = ai[3];
}

template<> EIGEN_STRONG_INLINE Packet4f plset<float>(const float& a) { return vec_add(pset1<Packet4f>(a), p4f_COUNTDOWN); }
template<> EIGEN_STRONG_INLINE Packet4i plset<int>(const int& a)     { return vec_add(pset1<Packet4i>(a), p4i_COUNTDOWN); }

template<> EIGEN_STRONG_INLINE Packet4f padd<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_add(a,b); }
template<> EIGEN_STRONG_INLINE Packet4i padd<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_add(a,b); }

template<> EIGEN_STRONG_INLINE Packet4f psub<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_sub(a,b); }
template<> EIGEN_STRONG_INLINE Packet4i psub<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_sub(a,b); }

template<> EIGEN_STRONG_INLINE Packet4f pnegate(const Packet4f& a) { return psub<Packet4f>(p4f_ZERO, a); }
template<> EIGEN_STRONG_INLINE Packet4i pnegate(const Packet4i& a) { return psub<Packet4i>(p4i_ZERO, a); }

template<> EIGEN_STRONG_INLINE Packet4f pconj(const Packet4f& a) { return a; }
template<> EIGEN_STRONG_INLINE Packet4i pconj(const Packet4i& a) { return a; }

template<> EIGEN_STRONG_INLINE Packet4f pmul<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_madd(a,b,p4f_ZERO); }
/* Commented out: it's actually slower than processing it scalar
 *
template<> EIGEN_STRONG_INLINE Packet4i pmul<Packet4i>(const Packet4i& a, const Packet4i& b)
{
  // Detailed in: http://freevec.org/content/32bit_signed_integer_multiplication_altivec
  //Set up constants, variables
  Packet4i a1, b1, bswap, low_prod, high_prod, prod, prod_, v1sel;

  // Get the absolute values
  a1  = vec_abs(a);
  b1  = vec_abs(b);

  // Get the signs using xor
  Packet4bi sgn = (Packet4bi) vec_cmplt(vec_xor(a, b), p4i_ZERO);

  // Do the multiplication for the asbolute values.
  bswap = (Packet4i) vec_rl((Packet4ui) b1, (Packet4ui) p4i_MINUS16 );
  low_prod = vec_mulo((Packet8i) a1, (Packet8i)b1);
  high_prod = vec_msum((Packet8i) a1, (Packet8i) bswap, p4i_ZERO);
  high_prod = (Packet4i) vec_sl((Packet4ui) high_prod, (Packet4ui) p4i_MINUS16);
  prod = vec_add( low_prod, high_prod );

  // NOR the product and select only the negative elements according to the sign mask
  prod_ = vec_nor(prod, prod);
  prod_ = vec_sel(p4i_ZERO, prod_, sgn);

  // Add 1 to the result to get the negative numbers
  v1sel = vec_sel(p4i_ZERO, p4i_ONE, sgn);
  prod_ = vec_add(prod_, v1sel);

  // Merge the results back to the final vector.
  prod = vec_sel(prod, prod_, sgn);

  return prod;
}
*/
template<> EIGEN_STRONG_INLINE Packet4f pdiv<Packet4f>(const Packet4f& a, const Packet4f& b)
{
#if !defined(__VSX__) // VSX actually provides a div instruction
  Packet4f t, y_0, y_1;

  // Altivec does not offer a divide instruction, we have to do a reciprocal approximation
  y_0 = vec_re(b);

  // Do one Newton-Raphson iteration to get the needed accuracy
  t   = vec_nmsub(y_0, b, p4f_ONE);
  y_1 = vec_madd(y_0, t, y_0);

  return vec_madd(a, y_1, p4f_ZERO);
#else
  return vec_div(a, b);
#endif
}

template<> EIGEN_STRONG_INLINE Packet4i pdiv<Packet4i>(const Packet4i& /*a*/, const Packet4i& /*b*/)
{ eigen_assert(false && "packet integer division are not supported by AltiVec");
  return pset1<Packet4i>(0);
}

// for some weird raisons, it has to be overloaded for packet of integers
template<> EIGEN_STRONG_INLINE Packet4f pmadd(const Packet4f& a, const Packet4f& b, const Packet4f& c) { return vec_madd(a, b, c); }
template<> EIGEN_STRONG_INLINE Packet4i pmadd(const Packet4i& a, const Packet4i& b, const Packet4i& c) { return padd(pmul(a,b), c); }

template<> EIGEN_STRONG_INLINE Packet4f pmin<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_min(a, b); }
template<> EIGEN_STRONG_INLINE Packet4i pmin<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_min(a, b); }

template<> EIGEN_STRONG_INLINE Packet4f pmax<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_max(a, b); }
template<> EIGEN_STRONG_INLINE Packet4i pmax<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_max(a, b); }

template<> EIGEN_STRONG_INLINE Packet4f pand<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_and(a, b); }
template<> EIGEN_STRONG_INLINE Packet4i pand<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_and(a, b); }

template<> EIGEN_STRONG_INLINE Packet4f por<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_or(a, b); }
template<> EIGEN_STRONG_INLINE Packet4i por<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_or(a, b); }

template<> EIGEN_STRONG_INLINE Packet4f pxor<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_xor(a, b); }
template<> EIGEN_STRONG_INLINE Packet4i pxor<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_xor(a, b); }

template<> EIGEN_STRONG_INLINE Packet4f pandnot<Packet4f>(const Packet4f& a, const Packet4f& b) { return vec_and(a, vec_nor(b, b)); }
template<> EIGEN_STRONG_INLINE Packet4i pandnot<Packet4i>(const Packet4i& a, const Packet4i& b) { return vec_and(a, vec_nor(b, b)); }

#ifdef _BIG_ENDIAN
template<> EIGEN_STRONG_INLINE Packet4f ploadu<Packet4f>(const float* from)
{
  EIGEN_DEBUG_ALIGNED_LOAD
  Packet16uc MSQ, LSQ;
  Packet16uc mask;
  MSQ = vec_ld(0, (unsigned char *)from);          // most significant quadword
  LSQ = vec_ld(15, (unsigned char *)from);         // least significant quadword
  mask = vec_lvsl(0, from);                        // create the permute mask
  return (Packet4f) vec_perm(MSQ, LSQ, mask);           // align the data

}
template<> EIGEN_STRONG_INLINE Packet4i ploadu<Packet4i>(const int* from)
{
  EIGEN_DEBUG_ALIGNED_LOAD
  // Taken from http://developer.apple.com/hardwaredrivers/ve/alignment.html
  Packet16uc MSQ, LSQ;
  Packet16uc mask;
  MSQ = vec_ld(0, (unsigned char *)from);          // most significant quadword
  LSQ = vec_ld(15, (unsigned char *)from);         // least significant quadword
  mask = vec_lvsl(0, from);                        // create the permute mask
  return (Packet4i) vec_perm(MSQ, LSQ, mask);    // align the data
}
#else
// We also need ot redefine little endian loading of Packet4i/Packet4f using VSX
template<> EIGEN_STRONG_INLINE Packet4i ploadu<Packet4i>(const int* from)
{
  EIGEN_DEBUG_ALIGNED_LOAD
  return (Packet4i) vec_vsx_ld((long)from & 15, (const Packet4i*) _EIGEN_ALIGNED_PTR(from));
}
template<> EIGEN_STRONG_INLINE Packet4f ploadu<Packet4f>(const float* from)
{
  EIGEN_DEBUG_ALIGNED_LOAD
  return (Packet4f) vec_vsx_ld((long)from & 15, (const Packet4f*) _EIGEN_ALIGNED_PTR(from));
}
#endif

template<> EIGEN_STRONG_INLINE Packet4f ploaddup<Packet4f>(const float*   from)
{
  Packet4f p;
  if((ptrdiff_t(from) % 16) == 0)  p = pload<Packet4f>(from);
  else                             p = ploadu<Packet4f>(from);
  return vec_perm(p, p, p16uc_DUPLICATE32_HI);
}
template<> EIGEN_STRONG_INLINE Packet4i ploaddup<Packet4i>(const int*     from)
{
  Packet4i p;
  if((ptrdiff_t(from) % 16) == 0)  p = pload<Packet4i>(from);
  else                             p = ploadu<Packet4i>(from);
  return vec_perm(p, p, p16uc_DUPLICATE32_HI);
}

#ifdef _BIG_ENDIAN
template<> EIGEN_STRONG_INLINE void pstoreu<float>(float*  to, const Packet4f& from)
{
  EIGEN_DEBUG_UNALIGNED_STORE
  // Taken from http://developer.apple.com/hardwaredrivers/ve/alignment.html
  // Warning: not thread safe!
  Packet16uc MSQ, LSQ, edges;
  Packet16uc edgeAlign, align;

  MSQ = vec_ld(0, (unsigned char *)to);                     // most significant quadword
  LSQ = vec_ld(15, (unsigned char *)to);                    // least significant quadword
  edgeAlign = vec_lvsl(0, to);                              // permute map to extract edges
  edges=vec_perm(LSQ,MSQ,edgeAlign);                        // extract the edges
  align = vec_lvsr( 0, to );                                // permute map to misalign data
  MSQ = vec_perm(edges,(Packet16uc)from,align);             // misalign the data (MSQ)
  LSQ = vec_perm((Packet16uc)from,edges,align);             // misalign the data (LSQ)
  vec_st( LSQ, 15, (unsigned char *)to );                   // Store the LSQ part first
  vec_st( MSQ, 0, (unsigned char *)to );                    // Store the MSQ part
}
template<> EIGEN_STRONG_INLINE void pstoreu<int>(int*      to, const Packet4i& from)
{
  EIGEN_DEBUG_UNALIGNED_STORE
  // Taken from http://developer.apple.com/hardwaredrivers/ve/alignment.html
  // Warning: not thread safe!
  Packet16uc MSQ, LSQ, edges;
  Packet16uc edgeAlign, align;

  MSQ = vec_ld(0, (unsigned char *)to);                     // most significant quadword
  LSQ = vec_ld(15, (unsigned char *)to);                    // least significant quadword
  edgeAlign = vec_lvsl(0, to);                              // permute map to extract edges
  edges=vec_perm(LSQ, MSQ, edgeAlign);                      // extract the edges
  align = vec_lvsr( 0, to );                                // permute map to misalign data
  MSQ = vec_perm(edges, (Packet16uc) from, align);          // misalign the data (MSQ)
  LSQ = vec_perm((Packet16uc) from, edges, align);          // misalign the data (LSQ)
  vec_st( LSQ, 15, (unsigned char *)to );                   // Store the LSQ part first
  vec_st( MSQ, 0, (unsigned char *)to );                    // Store the MSQ part
}
#else
// We also need to redefine little endian loading of Packet4i/Packet4f using VSX
template<> EIGEN_STRONG_INLINE void pstoreu<int>(int*       to, const Packet4i& from)
{
  EIGEN_DEBUG_ALIGNED_STORE
  vec_vsx_st(from, (long)to & 15, (Packet4i*) _EIGEN_ALIGNED_PTR(to));
}
template<> EIGEN_STRONG_INLINE void pstoreu<float>(float*   to, const Packet4f& from)
{
  EIGEN_DEBUG_ALIGNED_STORE
  vec_vsx_st(from, (long)to & 15, (Packet4f*) _EIGEN_ALIGNED_PTR(to));
}
#endif

#ifndef __VSX__
template<> EIGEN_STRONG_INLINE void prefetch<float>(const float* addr) { vec_dstt(addr, DST_CTRL(2,2,32), DST_CHAN); }
template<> EIGEN_STRONG_INLINE void prefetch<int>(const int*     addr) { vec_dstt(addr, DST_CTRL(2,2,32), DST_CHAN); }
#endif

template<> EIGEN_STRONG_INLINE float  pfirst<Packet4f>(const Packet4f& a) { float EIGEN_ALIGN16 x[4]; vec_st(a, 0, x); return x[0]; }
template<> EIGEN_STRONG_INLINE int    pfirst<Packet4i>(const Packet4i& a) { int   EIGEN_ALIGN16 x[4]; vec_st(a, 0, x); return x[0]; }

template<> EIGEN_STRONG_INLINE Packet4f preverse(const Packet4f& a) { return (Packet4f)vec_perm((Packet16uc)a,(Packet16uc)a, p16uc_REVERSE32); }
template<> EIGEN_STRONG_INLINE Packet4i preverse(const Packet4i& a) { return (Packet4i)vec_perm((Packet16uc)a,(Packet16uc)a, p16uc_REVERSE32); }

template<> EIGEN_STRONG_INLINE Packet4f pabs(const Packet4f& a) { return vec_abs(a); }
template<> EIGEN_STRONG_INLINE Packet4i pabs(const Packet4i& a) { return vec_abs(a); }

template<> EIGEN_STRONG_INLINE float predux<Packet4f>(const Packet4f& a)
{
  Packet4f b, sum;
  b   = (Packet4f) vec_sld(a, a, 8);
  sum = vec_add(a, b);
  b   = (Packet4f) vec_sld(sum, sum, 4);
  sum = vec_add(sum, b);
  return pfirst(sum);
}

template<> EIGEN_STRONG_INLINE Packet4f preduxp<Packet4f>(const Packet4f* vecs)
{
  Packet4f v[4], sum[4];

  // It's easier and faster to transpose then add as columns
  // Check: http://www.freevec.org/function/matrix_4x4_transpose_floats for explanation
  // Do the transpose, first set of moves
  v[0] = vec_mergeh(vecs[0], vecs[2]);
  v[1] = vec_mergel(vecs[0], vecs[2]);
  v[2] = vec_mergeh(vecs[1], vecs[3]);
  v[3] = vec_mergel(vecs[1], vecs[3]);
  // Get the resulting vectors
  sum[0] = vec_mergeh(v[0], v[2]);
  sum[1] = vec_mergel(v[0], v[2]);
  sum[2] = vec_mergeh(v[1], v[3]);
  sum[3] = vec_mergel(v[1], v[3]);

  // Now do the summation:
  // Lines 0+1
  sum[0] = vec_add(sum[0], sum[1]);
  // Lines 2+3
  sum[1] = vec_add(sum[2], sum[3]);
  // Add the results
  sum[0] = vec_add(sum[0], sum[1]);

  return sum[0];
}

template<> EIGEN_STRONG_INLINE int predux<Packet4i>(const Packet4i& a)
{
  Packet4i sum;
  sum = vec_sums(a, p4i_ZERO);
#ifdef _BIG_ENDIAN
  sum = vec_sld(sum, p4i_ZERO, 12);
#else
  sum = vec_sld(p4i_ZERO, sum, 4);
#endif
  return pfirst(sum);
}

template<> EIGEN_STRONG_INLINE Packet4i preduxp<Packet4i>(const Packet4i* vecs)
{
  Packet4i v[4], sum[4];

  // It's easier and faster to transpose then add as columns
  // Check: http://www.freevec.org/function/matrix_4x4_transpose_floats for explanation
  // Do the transpose, first set of moves
  v[0] = vec_mergeh(vecs[0], vecs[2]);
  v[1] = vec_mergel(vecs[0], vecs[2]);
  v[2] = vec_mergeh(vecs[1], vecs[3]);
  v[3] = vec_mergel(vecs[1], vecs[3]);
  // Get the resulting vectors
  sum[0] = vec_mergeh(v[0], v[2]);
  sum[1] = vec_mergel(v[0], v[2]);
  sum[2] = vec_mergeh(v[1], v[3]);
  sum[3] = vec_mergel(v[1], v[3]);

  // Now do the summation:
  // Lines 0+1
  sum[0] = vec_add(sum[0], sum[1]);
  // Lines 2+3
  sum[1] = vec_add(sum[2], sum[3]);
  // Add the results
  sum[0] = vec_add(sum[0], sum[1]);

  return sum[0];
}

// Other reduction functions:
// mul
template<> EIGEN_STRONG_INLINE float predux_mul<Packet4f>(const Packet4f& a)
{
  Packet4f prod;
  prod = pmul(a, (Packet4f)vec_sld(a, a, 8));
  return pfirst(pmul(prod, (Packet4f)vec_sld(prod, prod, 4)));
}

template<> EIGEN_STRONG_INLINE int predux_mul<Packet4i>(const Packet4i& a)
{
  EIGEN_ALIGN16 int aux[4];
  pstore(aux, a);
  return aux[0] * aux[1] * aux[2] * aux[3];
}

// min
template<> EIGEN_STRONG_INLINE float predux_min<Packet4f>(const Packet4f& a)
{
  Packet4f b, res;
  b = vec_min(a, vec_sld(a, a, 8));
  res = vec_min(b, vec_sld(b, b, 4));
  return pfirst(res);
}

template<> EIGEN_STRONG_INLINE int predux_min<Packet4i>(const Packet4i& a)
{
  Packet4i b, res;
  b = vec_min(a, vec_sld(a, a, 8));
  res = vec_min(b, vec_sld(b, b, 4));
  return pfirst(res);
}

// max
template<> EIGEN_STRONG_INLINE float predux_max<Packet4f>(const Packet4f& a)
{
  Packet4f b, res;
  b = vec_max(a, vec_sld(a, a, 8));
  res = vec_max(b, vec_sld(b, b, 4));
  return pfirst(res);
}

template<> EIGEN_STRONG_INLINE int predux_max<Packet4i>(const Packet4i& a)
{
  Packet4i b, res;
  b = vec_max(a, vec_sld(a, a, 8));
  res = vec_max(b, vec_sld(b, b, 4));
  return pfirst(res);
}

template<int Offset>
struct palign_impl<Offset,Packet4f>
{
  static EIGEN_STRONG_INLINE void run(Packet4f& first, const Packet4f& second)
  {
#ifdef _BIG_ENDIAN
    switch (Offset % 4) {
    case 1:
      first = vec_sld(first, second, 4); break;
    case 2:
      first = vec_sld(first, second, 8); break;
    case 3:
      first = vec_sld(first, second, 12); break;
    }
#else
    switch (Offset % 4) {
    case 1:
      first = vec_sld(second, first, 12); break;
    case 2:
      first = vec_sld(second, first, 8); break;
    case 3:
      first = vec_sld(second, first, 4); break;
    }
#endif
  }
};

template<int Offset>
struct palign_impl<Offset,Packet4i>
{
  static EIGEN_STRONG_INLINE void run(Packet4i& first, const Packet4i& second)
  {
#ifdef _BIG_ENDIAN
    switch (Offset % 4) {
    case 1:
      first = vec_sld(first, second, 4); break;
    case 2:
      first = vec_sld(first, second, 8); break;
    case 3:
      first = vec_sld(first, second, 12); break;
    }
#else
    switch (Offset % 4) {
    case 1:
      first = vec_sld(second, first, 12); break;
    case 2:
      first = vec_sld(second, first, 8); break;
    case 3:
      first = vec_sld(second, first, 4); break;
    }
#endif
  }
};

template<> EIGEN_DEVICE_FUNC inline void
ptranspose(PacketBlock<Packet4f,4>& kernel) {
  Packet4f t0, t1, t2, t3;
  t0 = vec_mergeh(kernel.packet[0], kernel.packet[2]);
  t1 = vec_mergel(kernel.packet[0], kernel.packet[2]);
  t2 = vec_mergeh(kernel.packet[1], kernel.packet[3]);
  t3 = vec_mergel(kernel.packet[1], kernel.packet[3]);
  kernel.packet[0] = vec_mergeh(t0, t2);
  kernel.packet[1] = vec_mergel(t0, t2);
  kernel.packet[2] = vec_mergeh(t1, t3);
  kernel.packet[3] = vec_mergel(t1, t3);
}

template<> EIGEN_DEVICE_FUNC inline void
ptranspose(PacketBlock<Packet4i,4>& kernel) {
  Packet4i t0, t1, t2, t3;
  t0 = vec_mergeh(kernel.packet[0], kernel.packet[2]);
  t1 = vec_mergel(kernel.packet[0], kernel.packet[2]);
  t2 = vec_mergeh(kernel.packet[1], kernel.packet[3]);
  t3 = vec_mergel(kernel.packet[1], kernel.packet[3]);
  kernel.packet[0] = vec_mergeh(t0, t2);
  kernel.packet[1] = vec_mergel(t0, t2);
  kernel.packet[2] = vec_mergeh(t1, t3);
  kernel.packet[3] = vec_mergel(t1, t3);
}


//---------- double ----------
#if defined(__VSX__)
typedef __vector double              Packet2d;
typedef __vector unsigned long long  Packet2ul;
typedef __vector long long           Packet2l;

static Packet2l p2l_ZERO = (Packet2l) p4i_ZERO;
static Packet2d p2d_ONE = { 1.0, 1.0 }; 
static Packet2d p2d_ZERO = (Packet2d) p4f_ZERO;
static Packet2d p2d_ZERO_ = { -0.0, -0.0 };

#ifdef _BIG_ENDIAN
static Packet2d p2d_COUNTDOWN = (Packet2d) vec_sld((Packet16uc) p2d_ZERO, (Packet16uc) p2d_ONE, 8);
#else
static Packet2d p2d_COUNTDOWN = (Packet2d) vec_sld((Packet16uc) p2d_ONE, (Packet16uc) p2d_ZERO, 8);
#endif

static EIGEN_STRONG_INLINE Packet2d vec_splat_dbl(Packet2d& a, int index)
{
  switch (index) {
  case 0:
    return (Packet2d) vec_perm(a, a, p16uc_PSET64_HI);
  case 1:
    return (Packet2d) vec_perm(a, a, p16uc_PSET64_LO);
  }
  return a;
}

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,
    HasSqrt = 0
  };
};

template<> struct unpacket_traits<Packet2d> { typedef double type; enum {size=2}; typedef Packet2d half; };


inline std::ostream & operator <<(std::ostream & s, const Packet2d & v)
{
  union {
    Packet2d   v;
    double n[2];
  } vt;
  vt.v = v;
  s << vt.n[0] << ", " << vt.n[1];
  return s;
}

// Need to define them first or we get specialization after instantiation errors
template<> EIGEN_STRONG_INLINE Packet2d pload<Packet2d>(const double* from) { EIGEN_DEBUG_ALIGNED_LOAD return (Packet2d) vec_ld(0, (const float *) from); } //FIXME

template<> EIGEN_STRONG_INLINE void pstore<double>(double*   to, const Packet2d& from) { EIGEN_DEBUG_ALIGNED_STORE vec_st((Packet4f)from, 0, (float *)to); }

template<> EIGEN_STRONG_INLINE Packet2d pset1<Packet2d>(const double&  from) {
  double EIGEN_ALIGN16 af[2];
  af[0] = from;
  Packet2d vc = pload<Packet2d>(af);
  vc = vec_splat_dbl(vc, 0);
  return vc;
}
template<> EIGEN_STRONG_INLINE void
pbroadcast4<Packet2d>(const double *a,
                      Packet2d& a0, Packet2d& a1, Packet2d& a2, Packet2d& a3)
{
  a1 = pload<Packet2d>(a);
  a0 = vec_splat_dbl(a1, 0);
  a1 = vec_splat_dbl(a1, 1);
  a3 = pload<Packet2d>(a+2);
  a2 = vec_splat_dbl(a3, 0);
  a3 = vec_splat_dbl(a3, 1);
}
// Google-local: Change type from DenseIndex to int in patch.
template<> EIGEN_DEVICE_FUNC inline Packet2d pgather<double, Packet2d>(const double* from, int/*DenseIndex*/ stride)
{
  double EIGEN_ALIGN16 af[2];
  af[0] = from[0*stride];
  af[1] = from[1*stride];
 return pload<Packet2d>(af);
}
template<> EIGEN_DEVICE_FUNC inline void pscatter<double, Packet2d>(double* to, const Packet2d& from, /*DenseIndex*/int stride)
{
  double EIGEN_ALIGN16 af[2];
  pstore<double>(af, from);
  to[0*stride] = af[0];
  to[1*stride] = af[1];
}
template<> EIGEN_STRONG_INLINE Packet2d plset<double>(const double& a) { return vec_add(pset1<Packet2d>(a), p2d_COUNTDOWN); }

template<> EIGEN_STRONG_INLINE Packet2d padd<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_add(a,b); }

template<> EIGEN_STRONG_INLINE Packet2d psub<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_sub(a,b); }

template<> EIGEN_STRONG_INLINE Packet2d pnegate(const Packet2d& a) { return psub<Packet2d>(p2d_ZERO, a); }

template<> EIGEN_STRONG_INLINE Packet2d pconj(const Packet2d& a) { return a; }

template<> EIGEN_STRONG_INLINE Packet2d pmul<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_madd(a,b,p2d_ZERO); }
template<> EIGEN_STRONG_INLINE Packet2d pdiv<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_div(a,b); }

// for some weird raisons, it has to be overloaded for packet of integers
template<> EIGEN_STRONG_INLINE Packet2d pmadd(const Packet2d& a, const Packet2d& b, const Packet2d& c) { return vec_madd(a, b, c); }

template<> EIGEN_STRONG_INLINE Packet2d pmin<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_min(a, b); }

template<> EIGEN_STRONG_INLINE Packet2d pmax<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_max(a, b); }

template<> EIGEN_STRONG_INLINE Packet2d pand<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_and(a, b); }

template<> EIGEN_STRONG_INLINE Packet2d por<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_or(a, b); }

template<> EIGEN_STRONG_INLINE Packet2d pxor<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_xor(a, b); }

template<> EIGEN_STRONG_INLINE Packet2d pandnot<Packet2d>(const Packet2d& a, const Packet2d& b) { return vec_and(a, vec_nor(b, b)); }

template<> EIGEN_STRONG_INLINE Packet2d ploadu<Packet2d>(const double* from)
{
  EIGEN_DEBUG_ALIGNED_LOAD
  return (Packet2d) vec_vsx_ld((long)from & 15, (const Packet2d*) _EIGEN_ALIGNED_PTR(from));
}
template<> EIGEN_STRONG_INLINE Packet2d ploaddup<Packet2d>(const double*   from)
{
  Packet2d p;
  if((ptrdiff_t(from) % 16) == 0)  p = pload<Packet2d>(from);
  else                             p = ploadu<Packet2d>(from);
  return vec_perm(p, p, p16uc_PSET64_HI);
}

template<> EIGEN_STRONG_INLINE void pstoreu<double>(double*  to, const Packet2d& from)
{
  EIGEN_DEBUG_ALIGNED_STORE
  vec_vsx_st((Packet4f)from, (long)to & 15, (Packet4f*) _EIGEN_ALIGNED_PTR(to));
}

#ifndef __VSX__
template<> EIGEN_STRONG_INLINE void prefetch<double>(const double* addr) { vec_dstt((const float *) addr, DST_CTRL(2,2,32), DST_CHAN); }
#endif

template<> EIGEN_STRONG_INLINE double  pfirst<Packet2d>(const Packet2d& a) { double EIGEN_ALIGN16 x[2]; pstore(x, a); return x[0]; }

template<> EIGEN_STRONG_INLINE Packet2d preverse(const Packet2d& a) { return (Packet2d)vec_perm((Packet16uc)a,(Packet16uc)a, p16uc_REVERSE64); }

template<> EIGEN_STRONG_INLINE Packet2d pabs(const Packet2d& a) { return vec_abs(a); }

template<> EIGEN_STRONG_INLINE double predux<Packet2d>(const Packet2d& a)
{
  Packet2d b, sum;
  b   = (Packet2d) vec_sld((Packet4ui) a, (Packet4ui)a, 8);
  sum = vec_add(a, b);
  return pfirst(sum);
}

template<> EIGEN_STRONG_INLINE Packet2d preduxp<Packet2d>(const Packet2d* vecs)
{
  Packet2d v[2], sum;
  v[0] = vec_add(vecs[0], (Packet2d) vec_sld((Packet4ui) vecs[0], (Packet4ui) vecs[0], 8));
  v[1] = vec_add(vecs[1], (Packet2d) vec_sld((Packet4ui) vecs[1], (Packet4ui) vecs[1], 8));
 
#ifdef _BIG_ENDIAN
 sum = (Packet2d) vec_sld((Packet4ui) v[0], (Packet4ui) v[1], 8);
#else
  sum = (Packet2d) vec_sld((Packet4ui) v[1], (Packet4ui) v[0], 8);
#endif

  return sum;
}
// Other reduction functions:
// mul
template<> EIGEN_STRONG_INLINE double predux_mul<Packet2d>(const Packet2d& a)
{
  return pfirst(pmul(a, (Packet2d)vec_sld((Packet4ui) a, (Packet4ui) a, 8)));
}

// min
template<> EIGEN_STRONG_INLINE double predux_min<Packet2d>(const Packet2d& a)
{
  return pfirst(vec_min(a, (Packet2d) vec_sld((Packet4ui) a, (Packet4ui) a, 8)));
}

// max
template<> EIGEN_STRONG_INLINE double predux_max<Packet2d>(const Packet2d& a)
{
  return pfirst(vec_max(a, (Packet2d) vec_sld((Packet4ui) a, (Packet4ui) a, 8)));
}

template<int Offset>
struct palign_impl<Offset,Packet2d>
{
  static EIGEN_STRONG_INLINE void run(Packet2d& first, const Packet2d& second)
  {
    if (Offset == 1)
#ifdef _BIG_ENDIAN
      first = (Packet2d) vec_sld((Packet4ui) first, (Packet4ui) second, 8);
#else
      first = (Packet2d) vec_sld((Packet4ui) second, (Packet4ui) first, 8);
#endif
  }
};

EIGEN_DEVICE_FUNC inline void
ptranspose(PacketBlock<Packet2d,2>& kernel) {
  Packet2d t0, t1;
  t0 = vec_perm(kernel.packet[0], kernel.packet[1], p16uc_TRANSPOSE64_HI);
  t1 = vec_perm(kernel.packet[0], kernel.packet[1], p16uc_TRANSPOSE64_LO);
  kernel.packet[0] = t0;
  kernel.packet[1] = t1;
}

#endif  // defined(__VSX__)
} // end namespace internal

} // end namespace Eigen

#endif // EIGEN_PACKET_MATH_ALTIVEC_H