From 65186ef18d6212b3d09b1d619f1cf1019c2ae0fb Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Thu, 6 Aug 2015 14:07:59 +0200
Subject: [PATCH] Fix logic in compute_default_alignment, extend it to Dynamic
 size, and move it to XprHelper.h file.

---
 Eigen/src/Core/DenseStorage.h   | 27 +++--------------------
 Eigen/src/Core/util/XprHelper.h | 39 +++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 24 deletions(-)

diff --git a/Eigen/src/Core/DenseStorage.h b/Eigen/src/Core/DenseStorage.h
index 5edf8a4ee..340484610 100644
--- a/Eigen/src/Core/DenseStorage.h
+++ b/Eigen/src/Core/DenseStorage.h
@@ -34,34 +34,13 @@ void check_static_allocation_size()
   #endif
 }
 
-template<int ArrayBytes, int AlignmentBytes,
-         bool Match     =  bool((ArrayBytes%AlignmentBytes)==0),
-         bool TryHalf   =  bool(AlignmentBytes>EIGEN_MIN_ALIGN_BYTES) >
-struct compute_default_alignment
-{
-  enum { value = 0 };
-};
-
-template<int ArrayBytes, int AlignmentBytes, bool TryHalf>
-struct compute_default_alignment<ArrayBytes, AlignmentBytes, true, TryHalf> // Match
-{
-  enum { value = AlignmentBytes };
-};
-
-template<int ArrayBytes, int AlignmentBytes>
-struct compute_default_alignment<ArrayBytes, AlignmentBytes, false, true> // Try-half
-{
-  // current packet too large, try with an half-packet
-  enum { value = compute_default_alignment<ArrayBytes, AlignmentBytes/2>::value };
-};
-
 /** \internal
   * Static array. If the MatrixOrArrayOptions require auto-alignment, the array will be automatically aligned:
   * to 16 bytes boundary if the total size is a multiple of 16 bytes.
   */
 template <typename T, int Size, int MatrixOrArrayOptions,
           int Alignment = (MatrixOrArrayOptions&DontAlign) ? 0
-                        : compute_default_alignment<Size*sizeof(T), EIGEN_PLAIN_ENUM_MAX(packet_traits<T>::size*sizeof(T), EIGEN_MAX_STATIC_ALIGN_BYTES) >::value >
+                        : compute_default_alignment<T,Size>::value >
 struct plain_array
 {
   T array[Size];
@@ -107,7 +86,7 @@ struct plain_array<T, Size, MatrixOrArrayOptions, 8>
 
   EIGEN_DEVICE_FUNC
   plain_array() 
-  { 
+  {
     EIGEN_MAKE_UNALIGNED_ARRAY_ASSERT(7);
     check_static_allocation_size<T,Size>();
   }
@@ -145,7 +124,7 @@ struct plain_array<T, Size, MatrixOrArrayOptions, 32>
 
   EIGEN_DEVICE_FUNC
   plain_array() 
-  { 
+  {
     EIGEN_MAKE_UNALIGNED_ARRAY_ASSERT(31);
     check_static_allocation_size<T,Size>();
   }
diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 433e816af..6dc1f6e3f 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -122,6 +122,45 @@ template<typename T> struct unpacket_traits
   enum {size=1};
 };
 
+#if EIGEN_MAX_STATIC_ALIGN_BYTES>0
+template<int ArrayBytes, int AlignmentBytes,
+         bool Match     =  bool((ArrayBytes%AlignmentBytes)==0),
+         bool TryHalf   =  bool(AlignmentBytes>EIGEN_MIN_ALIGN_BYTES) >
+struct compute_default_alignment_helper
+{
+  enum { value = 0 };
+};
+
+template<int ArrayBytes, int AlignmentBytes, bool TryHalf>
+struct compute_default_alignment_helper<ArrayBytes, AlignmentBytes, true, TryHalf> // Match
+{
+  enum { value = AlignmentBytes };
+};
+
+template<int ArrayBytes, int AlignmentBytes>
+struct compute_default_alignment_helper<ArrayBytes, AlignmentBytes, false, true> // Try-half
+{
+  // current packet too large, try with an half-packet
+  enum { value = compute_default_alignment_helper<ArrayBytes, AlignmentBytes/2>::value };
+};
+#else
+// If static alignment is disabled, no need to bother.
+// This also avoids a division by zero in "bool Match =  bool((ArrayBytes%AlignmentBytes)==0)"
+template<int ArrayBytes, int AlignmentBytes>
+struct compute_default_alignment_helper
+{
+  enum { value = 0 };
+};
+#endif
+
+template<typename T, int Size> struct compute_default_alignment {
+  enum { value = compute_default_alignment_helper<Size*sizeof(T),EIGEN_MAX_STATIC_ALIGN_BYTES>::value };
+};
+
+template<typename T> struct compute_default_alignment<T,Dynamic> {
+  enum { value = EIGEN_MAX_ALIGN_BYTES };
+};
+
 template<typename _Scalar, int _Rows, int _Cols,
          int _Options = AutoAlign |
                           ( (_Rows==1 && _Cols!=1) ? RowMajor