Fix ldexp implementations.

The previous implementations produced garbage values if the exponent did
not fit within the exponent bits.  See #2131 for a complete discussion,
and !375 for other possible implementations.

Here we implement the 4-factor version. See `pldexp_impl` in
`GenericPacketMathFunctions.h` for a full description.

The SSE `pcmp*` methods were moved down since `pcmp_le<Packet4i>`
requires `por`.

Left as a "TODO" is to delegate to a faster version if we know the
exponent does fit within the exponent bits.

Fixes #2131.

1 files changed, 1 insertions, 23 deletions

diff --git a/Eigen/src/Core/GenericPacketMath.h b/Eigen/src/Core/GenericPacketMath.h
index 7160fa084..f8c7826db 100644
--- a/Eigen/src/Core/GenericPacketMath.h
+++ b/Eigen/src/Core/GenericPacketMath.h
@@ -453,7 +453,7 @@ EIGEN_DEVICE_FUNC inline Packet pfrexp(const Packet& a, Packet& exponent) {
   return result;
 }
 
-/** \internal \returns a * 2^exponent
+/** \internal \returns a * 2^((int)exponent)
   * See https://en.cppreference.com/w/cpp/numeric/math/ldexp
   */
 template<typename Packet> EIGEN_DEVICE_FUNC inline Packet
@@ -905,28 +905,6 @@ pblend(const Selector<unpacket_traits<Packet>::size>& ifPacket, const Packet& th
   return ifPacket.select[0] ? thenPacket : elsePacket;
 }
 
-/***************************************************************************
- * Some generic implementations to be used by implementors
-***************************************************************************/
-
-/** Default implementation of pfrexp for float.
-  * It is expected to be called by implementers of template<> pfrexp.
-  */
-template<typename Packet> EIGEN_STRONG_INLINE Packet
-pfrexp_float(const Packet& a, Packet& exponent);
-
-/** Default implementation of pldexp for float.
-  * It is expected to be called by implementers of template<> pldexp.
-  */
-template<typename Packet> EIGEN_STRONG_INLINE Packet
-pldexp_float(Packet a, Packet exponent);
-
-/** Default implementation of pldexp for double.
-  * It is expected to be called by implementers of template<> pldexp.
-  */
-template<typename Packet> EIGEN_STRONG_INLINE Packet
-pldexp_double(Packet a, Packet exponent);
-
 } // end namespace internal
 
 } // end namespace Eigen