Add a pinsertlast function replacing the last entry of a packet by a scalar.

(useful to vectorize LinSpaced)

4 files changed, 53 insertions, 0 deletions

diff --git a/Eigen/src/Core/GenericPacketMath.h b/Eigen/src/Core/GenericPacketMath.h
index 2d17f9ad1..9618b489c 100644
--- a/Eigen/src/Core/GenericPacketMath.h
+++ b/Eigen/src/Core/GenericPacketMath.h
@@ -558,6 +558,19 @@ pblend(const Selector<unpacket_traits<Packet>::size>& ifPacket, const Packet& th
   return ifPacket.select[0] ? thenPacket : elsePacket;
 }
 
+/** \internal \returns \a a with last coefficients replaced by the scalar b */
+template<typename Packet> EIGEN_DEVICE_FUNC Packet pinsertlast(const Packet& a, typename unpacket_traits<Packet>::type b)
+{
+  // Default implementation based on pblend.
+  // It must be specialized for higher performance.
+  Selector<unpacket_traits<Packet>::size> mask;
+  // This for loop should be optimized away by the compiler.
+  for(Index i=0; i<unpacket_traits<Packet>::size-1; ++i)
+    mask.select[i] = false;
+  mask.select[unpacket_traits<Packet>::size-1] = true;
+  return pblend(mask, pset1<Packet>(b), a);
+}
+
 } // end namespace internal
 
 } // end namespace Eigen
diff --git a/Eigen/src/Core/arch/AVX/PacketMath.h b/Eigen/src/Core/arch/AVX/PacketMath.h
index dae0ca5d0..8fb844982 100644
--- a/Eigen/src/Core/arch/AVX/PacketMath.h
+++ b/Eigen/src/Core/arch/AVX/PacketMath.h
@@ -604,6 +604,16 @@ template<> EIGEN_STRONG_INLINE Packet4d pblend(const Selector<4>& ifPacket, cons
   return _mm256_blendv_pd(thenPacket, elsePacket, false_mask);
 }
 
+template<> EIGEN_DEVICE_FUNC Packet8f pinsertlast(const Packet8f& a, float b)
+{
+  return _mm256_blend_ps(a,pset1<Packet8f>(b),(1<<7));
+}
+
+template<> EIGEN_DEVICE_FUNC Packet4d pinsertlast(const Packet4d& a, double b)
+{
+  return _mm256_blend_pd(a,pset1<Packet4d>(b),(1<<3));
+}
+
 } // end namespace internal
 
 } // end namespace Eigen
diff --git a/Eigen/src/Core/arch/SSE/PacketMath.h b/Eigen/src/Core/arch/SSE/PacketMath.h
index baad692e3..a28857873 100755
--- a/Eigen/src/Core/arch/SSE/PacketMath.h
+++ b/Eigen/src/Core/arch/SSE/PacketMath.h
@@ -818,6 +818,26 @@ template<> EIGEN_STRONG_INLINE Packet2d pblend(const Selector<2>& ifPacket, cons
 #endif
 }
 
+template<> EIGEN_DEVICE_FUNC Packet4f pinsertlast(const Packet4f& a, float b)
+{
+#ifdef EIGEN_VECTORIZE_SSE4_1
+  return _mm_blend_ps(a,pset1<Packet4f>(b),(1<<3));
+#else
+  const Packet4f mask = _mm_castsi128_ps(_mm_setr_epi32(0x0,0x0,0x0,0xFFFFFFFF));
+  return _mm_or_ps(_mm_andnot_pd(mask, a), _mm_and_pd(mask, pset1<Packet4f>(b)));
+#endif
+}
+
+template<> EIGEN_DEVICE_FUNC Packet2d pinsertlast(const Packet2d& a, double b)
+{
+#ifdef EIGEN_VECTORIZE_SSE4_1
+  return _mm_blend_pd(a,pset1<Packet2d>(b),(1<<1));
+#else
+  const Packet2d mask = _mm_castsi128_pd(_mm_setr_epi32(0x0,0x0,0xFFFFFFFF,0xFFFFFFFF));
+  return _mm_or_pd(_mm_andnot_pd(mask, a), _mm_and_pd(mask, pset1<Packet2d>(b)));
+#endif
+}
+
 // Scalar path for pmadd with FMA to ensure consistency with vectorized path.
 #ifdef __FMA__
 template<> EIGEN_STRONG_INLINE float pmadd(const float& a, const float& b, const float& c) {
diff --git a/test/packetmath.cpp b/test/packetmath.cpp
index c3d3e1521..a53786ae5 100644
--- a/test/packetmath.cpp
+++ b/test/packetmath.cpp
@@ -289,6 +289,16 @@ template<typename Scalar> void packetmath()
       VERIFY(isApproxAbs(result[i], (selector.select[i] ? data1[i] : data2[i]), refvalue));
     }
   }
+
+  if (PacketTraits::HasBlend) {
+    // pinsertlast
+    for (int i=0; i<PacketSize; ++i)
+      ref[i] = data1[i];
+    Scalar s = internal::random<Scalar>();
+    ref[PacketSize-1] = s;
+    internal::pstore(data2, internal::pinsertlast(internal::pload<Packet>(data1),s));
+    VERIFY(areApprox(ref, data2, PacketSize) && "internal::pinsertlast");
+  }
 }
 
 template<typename Scalar> void packetmath_real()