From 9d6d0dff8f0c1e8630996c3a4867ff0599566b33 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Sat, 1 Oct 2016 15:37:00 +0200
Subject: [PATCH] bug #1317: fix performance regression with some Block
 expressions and clang by helping it to remove dead code. The trick is to get
 rid of the nested expression in the evaluator by copying only the required
 information (here, the strides).

---
 Eigen/src/Core/CoreEvaluators.h | 52 ++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/Eigen/src/Core/CoreEvaluators.h b/Eigen/src/Core/CoreEvaluators.h
index 7a5540593..00c079bd8 100644
--- a/Eigen/src/Core/CoreEvaluators.h
+++ b/Eigen/src/Core/CoreEvaluators.h
@@ -817,73 +817,79 @@ struct mapbase_evaluator : evaluator_base<Derived>
     ColsAtCompileTime = XprType::ColsAtCompileTime,
     CoeffReadCost = NumTraits<Scalar>::ReadCost
   };
-  
+
   EIGEN_DEVICE_FUNC explicit mapbase_evaluator(const XprType& map)
-    : m_data(const_cast<PointerType>(map.data())),  
-      m_xpr(map)
+    : m_data(const_cast<PointerType>(map.data())),
+      m_innerStride(map.innerStride()),
+      m_outerStride(map.outerStride())
   {
     EIGEN_STATIC_ASSERT(EIGEN_IMPLIES(evaluator<Derived>::Flags&PacketAccessBit, internal::inner_stride_at_compile_time<Derived>::ret==1),
                         PACKET_ACCESS_REQUIRES_TO_HAVE_INNER_STRIDE_FIXED_TO_1);
     EIGEN_INTERNAL_CHECK_COST_VALUE(CoeffReadCost);
   }
- 
+
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   CoeffReturnType coeff(Index row, Index col) const
   {
-    return m_data[col * m_xpr.colStride() + row * m_xpr.rowStride()];
+    return m_data[col * colStride() + row * rowStride()];
   }
-  
+
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   CoeffReturnType coeff(Index index) const
   {
-    return m_data[index * m_xpr.innerStride()];
+    return m_data[index * m_innerStride.value()];
   }
 
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   Scalar& coeffRef(Index row, Index col)
   {
-    return m_data[col * m_xpr.colStride() + row * m_xpr.rowStride()];
+    return m_data[col * colStride() + row * rowStride()];
   }
-  
+
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
   Scalar& coeffRef(Index index)
   {
-    return m_data[index * m_xpr.innerStride()];
+    return m_data[index * m_innerStride.value()];
   }
- 
+
   template<int LoadMode, typename PacketType>
   EIGEN_STRONG_INLINE
-  PacketType packet(Index row, Index col) const 
+  PacketType packet(Index row, Index col) const
   {
-    PointerType ptr = m_data + row * m_xpr.rowStride() + col * m_xpr.colStride();
+    PointerType ptr = m_data + row * rowStride() + col * colStride();
     return internal::ploadt<PacketType, LoadMode>(ptr);
   }
 
   template<int LoadMode, typename PacketType>
   EIGEN_STRONG_INLINE
-  PacketType packet(Index index) const 
+  PacketType packet(Index index) const
   {
-    return internal::ploadt<PacketType, LoadMode>(m_data + index * m_xpr.innerStride());
+    return internal::ploadt<PacketType, LoadMode>(m_data + index * m_innerStride.value());
   }
-  
+
   template<int StoreMode, typename PacketType>
   EIGEN_STRONG_INLINE
-  void writePacket(Index row, Index col, const PacketType& x) 
+  void writePacket(Index row, Index col, const PacketType& x)
   {
-    PointerType ptr = m_data + row * m_xpr.rowStride() + col * m_xpr.colStride();
+    PointerType ptr = m_data + row * rowStride() + col * colStride();
     return internal::pstoret<Scalar, PacketType, StoreMode>(ptr, x);
   }
-  
+
   template<int StoreMode, typename PacketType>
   EIGEN_STRONG_INLINE
-  void writePacket(Index index, const PacketType& x) 
+  void writePacket(Index index, const PacketType& x)
   {
-    internal::pstoret<Scalar, PacketType, StoreMode>(m_data + index * m_xpr.innerStride(), x);
+    internal::pstoret<Scalar, PacketType, StoreMode>(m_data + index * m_innerStride.value(), x);
   }
- 
 protected:
+  EIGEN_DEVICE_FUNC
+  inline Index rowStride() const { return XprType::IsRowMajor ? m_outerStride.value() : m_innerStride.value(); }
+  EIGEN_DEVICE_FUNC
+  inline Index colStride() const { return XprType::IsRowMajor ? m_innerStride.value() : m_outerStride.value(); }
+
   PointerType m_data;
-  const XprType& m_xpr;
+  const internal::variable_if_dynamic<Index, XprType::InnerStrideAtCompileTime> m_innerStride;
+  const internal::variable_if_dynamic<Index, XprType::OuterStrideAtCompileTime> m_outerStride;
 };
 
 template<typename PlainObjectType, int MapOptions, typename StrideType>