* extend Map to allow the user to specify whether the mapped data

  is aligned or not. This is done using the Aligned constant:
  Map<MatrixType,Aligned>::Map(data);
* rename ForceAligned to EnforceAlignedAccess, and update its doc,
  and emphasize this is mainly an internal stuff.

1 files changed, 28 insertions, 12 deletions

diff --git a/Eigen/src/Core/MapBase.h b/Eigen/src/Core/MapBase.h
index 88a3fac1e..8770732de 100644
--- a/Eigen/src/Core/MapBase.h
+++ b/Eigen/src/Core/MapBase.h
@@ -32,11 +32,17 @@
   *
   * Expression classes inheriting MapBase must define the constant \c PacketAccess,
   * and type \c AlignedDerivedType in their respective ei_traits<> specialization structure.
-  * The value of \c PacketAccess can be either:
-  *  - \b ForceAligned which enforces both aligned loads and stores
-  *  - \b AsRequested which is the default behavior
+  * The value of \c PacketAccess can be either \b AsRequested, or set to \b EnforceAlignedAccess which
+  * enforces both aligned loads and stores.
+  * 
+  * \c EnforceAlignedAccess is automatically set in expressions such as 
+  * \code A += B; \endcode where A is either a Block or a Map. Here,
+  * this expression is transfomed into \code A = A_with_EnforceAlignedAccess + B; \endcode
+  * avoiding unaligned loads from A. Indeed, since Eigen's packet evaluation mechanism
+  * automatically align to the destination matrix, we know that loads to A will be aligned too.
+  * 
   * The type \c AlignedDerivedType should correspond to the equivalent expression type
-  * with \c PacketAccess being \c ForceAligned.
+  * with \c PacketAccess set to \c EnforceAlignedAccess.
   *
   * \sa class Map, class Block
   */
@@ -79,19 +85,19 @@ template<typename Derived> class MapBase
       * \sa MapBase::stride() */
     inline const Scalar* data() const { return m_data; }
 
-    template<bool IsForceAligned,typename Dummy> struct force_aligned_impl {
+    template<bool IsEnforceAlignedAccess,typename Dummy> struct force_aligned_impl {
       static AlignedDerivedType run(MapBase& a) { return a.derived(); }
     };
 
     template<typename Dummy> struct force_aligned_impl<false,Dummy> {
-      static AlignedDerivedType run(MapBase& a) { return a.derived()._convertToForceAligned(); }
+      static AlignedDerivedType run(MapBase& a) { return a.derived()._convertToEnforceAlignedAccess(); }
     };
 
     /** \returns an expression equivalent to \c *this but having the \c PacketAccess constant
-      * set to \c ForceAligned. Must be reimplemented by the derived class. */
+      * set to \c EnforceAlignedAccess. Must be reimplemented by the derived class. */
     AlignedDerivedType forceAligned()
     {
-      return force_aligned_impl<int(PacketAccess)==int(ForceAligned),Derived>::run(*this);
+      return force_aligned_impl<int(PacketAccess)==int(EnforceAlignedAccess),Derived>::run(*this);
     }
 
     inline const Scalar& coeff(int row, int col) const
@@ -131,7 +137,7 @@ template<typename Derived> class MapBase
     template<int LoadMode>
     inline PacketScalar packet(int row, int col) const
     {
-      return ei_ploadt<Scalar, int(PacketAccess) == ForceAligned ? Aligned : LoadMode>
+      return ei_ploadt<Scalar, int(PacketAccess) == EnforceAlignedAccess ? Aligned : LoadMode>
                (m_data + (IsRowMajor ? col + row * stride()
                                      : row + col * stride()));
     }
@@ -139,13 +145,13 @@ template<typename Derived> class MapBase
     template<int LoadMode>
     inline PacketScalar packet(int index) const
     {
-      return ei_ploadt<Scalar, int(PacketAccess) == ForceAligned ? Aligned : LoadMode>(m_data + index);
+      return ei_ploadt<Scalar, int(PacketAccess) == EnforceAlignedAccess ? Aligned : LoadMode>(m_data + index);
     }
 
     template<int StoreMode>
     inline void writePacket(int row, int col, const PacketScalar& x)
     {
-      ei_pstoret<Scalar, PacketScalar, int(PacketAccess) == ForceAligned ? Aligned : StoreMode>
+      ei_pstoret<Scalar, PacketScalar, int(PacketAccess) == EnforceAlignedAccess ? Aligned : StoreMode>
                (const_cast<Scalar*>(m_data) + (IsRowMajor ? col + row * stride()
                                                           : row + col * stride()), x);
     }
@@ -153,13 +159,14 @@ template<typename Derived> class MapBase
     template<int StoreMode>
     inline void writePacket(int index, const PacketScalar& x)
     {
-      ei_pstoret<Scalar, PacketScalar, int(PacketAccess) == ForceAligned ? Aligned : StoreMode>
+      ei_pstoret<Scalar, PacketScalar, int(PacketAccess) == EnforceAlignedAccess ? Aligned : StoreMode>
         (const_cast<Scalar*>(m_data) + index, x);
     }
 
     inline MapBase(const Scalar* data) : m_data(data), m_rows(RowsAtCompileTime), m_cols(ColsAtCompileTime)
     {
       EIGEN_STATIC_ASSERT_FIXED_SIZE(Derived)
+      checkDataAlignment();
     }
 
     inline MapBase(const Scalar* data, int size)
@@ -170,6 +177,7 @@ template<typename Derived> class MapBase
       EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived)
       ei_assert(size >= 0);
       ei_assert(data == 0 || SizeAtCompileTime == Dynamic || SizeAtCompileTime == size);
+      checkDataAlignment();
     }
 
     inline MapBase(const Scalar* data, int rows, int cols)
@@ -178,6 +186,7 @@ template<typename Derived> class MapBase
       ei_assert( (data == 0)
               || (   rows >= 0 && (RowsAtCompileTime == Dynamic || RowsAtCompileTime == rows)
                   && cols >= 0 && (ColsAtCompileTime == Dynamic || ColsAtCompileTime == cols)));
+      checkDataAlignment();
     }
 
     Derived& operator=(const MapBase& other)
@@ -215,6 +224,13 @@ template<typename Derived> class MapBase
     { return derived() = forceAligned() / other; }
 
   protected:
+
+    void checkDataAlignment() const
+    {
+      ei_assert( ((!(ei_traits<Derived>::Flags&AlignedBit))
+                  || ((std::size_t(m_data)&0xf)==0)) && "data is not aligned");
+    }
+    
     const Scalar* EIGEN_RESTRICT m_data;
     const ei_int_if_dynamic<RowsAtCompileTime> m_rows;
     const ei_int_if_dynamic<ColsAtCompileTime> m_cols;