+ * trans-types.c: Update copyright years.

+       * trans-types.c: Update copyright years.  Reformat long comment
+       explaining array descriptor format.  Remove obsolete mention of
+       TYPE_SET.
+

From-SVN: r123753

2 files changed, 42 insertions, 37 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 1ea9178..58b790b 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,5 +1,9 @@
 2007-04-12  Tobias Schlüter  <tobi@gcc.gnu.org>
 
+	* trans-types.c: Update copyright years.  Reformat long comment
+	explaining array descriptor format.  Remove obsolete mention of
+	TYPE_SET.
+
 	* arith.c (gfc_arith_uplus): Rename to ...
 	(gfc_arith_identity): ... this.
 	(gfc_parentheses): New function.
diff --git a/gcc/fortran/trans-types.c b/gcc/fortran/trans-types.c
index c0233a1..24a3f3c 100644
--- a/gcc/fortran/trans-types.c
+++ b/gcc/fortran/trans-types.c
@@ -1,6 +1,6 @@
 /* Backend support for Fortran 95 basic types and derived types.
-   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation,
-   Inc.
+   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 Free Software
+   Foundation, Inc.
    Contributed by Paul Brook <paul@nowt.org>
    and Steven Bosscher <s.bosscher@student.tudelft.nl>
 
@@ -755,7 +755,7 @@ gfc_get_element_type (tree type)
   return element;
 }
 
-/* Build an array. This function is called from gfc_sym_type().
+/* Build an array.  This function is called from gfc_sym_type().
    Actually returns array descriptor type.
 
    Format of array descriptors is as follows:
@@ -775,54 +775,55 @@ gfc_get_element_type (tree type)
       index ubound;
     }
 
-   Translation code should use gfc_conv_descriptor_* rather than accessing
-   the descriptor directly. Any changes to the array descriptor type will
-   require changes in gfc_conv_descriptor_* and gfc_build_array_initializer.
+   Translation code should use gfc_conv_descriptor_* rather than
+   accessing the descriptor directly.  Any changes to the array
+   descriptor type will require changes in gfc_conv_descriptor_* and
+   gfc_build_array_initializer.
 
-   This is represented internally as a RECORD_TYPE. The index nodes are
-   gfc_array_index_type and the data node is a pointer to the data. See below
-   for the handling of character types.
+   This is represented internally as a RECORD_TYPE. The index nodes
+   are gfc_array_index_type and the data node is a pointer to the
+   data.  See below for the handling of character types.
 
    The dtype member is formatted as follows:
     rank = dtype & GFC_DTYPE_RANK_MASK // 3 bits
     type = (dtype & GFC_DTYPE_TYPE_MASK) >> GFC_DTYPE_TYPE_SHIFT // 3 bits
     size = dtype >> GFC_DTYPE_SIZE_SHIFT
 
-   I originally used nested ARRAY_TYPE nodes to represent arrays, but this
-   generated poor code for assumed/deferred size arrays.  These require
-   use of PLACEHOLDER_EXPR/WITH_RECORD_EXPR, which isn't part of the GENERIC
-   grammar.  Also, there is no way to explicitly set the array stride, so
-   all data must be packed(1).  I've tried to mark all the functions which
-   would require modification with a GCC ARRAYS comment.
+   I originally used nested ARRAY_TYPE nodes to represent arrays, but
+   this generated poor code for assumed/deferred size arrays.  These
+   require use of PLACEHOLDER_EXPR/WITH_RECORD_EXPR, which isn't part
+   of the GENERIC grammar.  Also, there is no way to explicitly set
+   the array stride, so all data must be packed(1).  I've tried to
+   mark all the functions which would require modification with a GCC
+   ARRAYS comment.
 
-   The data component points to the first element in the array.
-   The offset field is the position of the origin of the array
-   (ie element (0, 0 ...)).  This may be outsite the bounds of the array.
+   The data component points to the first element in the array.  The
+   offset field is the position of the origin of the array (ie element
+   (0, 0 ...)).  This may be outsite the bounds of the array.
 
    An element is accessed by
-   data[offset + index0*stride0 + index1*stride1 + index2*stride2]
+    data[offset + index0*stride0 + index1*stride1 + index2*stride2]
    This gives good performance as the computation does not involve the
-   bounds of the array.  For packed arrays, this is optimized further by
-   substituting the known strides.
+   bounds of the array.  For packed arrays, this is optimized further
+   by substituting the known strides.
 
-   This system has one problem: all array bounds must be withing 2^31 elements
-   of the origin (2^63 on 64-bit machines).  For example
-   integer, dimension (80000:90000, 80000:90000, 2) :: array
-   may not work properly on 32-bit machines because 80000*80000 > 2^31, so
-   the calculation for stride02 would overflow.  This may still work, but
-   I haven't checked, and it relies on the overflow doing the right thing.
+   This system has one problem: all array bounds must be within 2^31
+   elements of the origin (2^63 on 64-bit machines).  For example
+    integer, dimension (80000:90000, 80000:90000, 2) :: array
+   may not work properly on 32-bit machines because 80000*80000 >
+   2^31, so the calculation for stride02 would overflow.  This may
+   still work, but I haven't checked, and it relies on the overflow
+   doing the right thing.
 
    The way to fix this problem is to access elements as follows:
-   data[(index0-lbound0)*stride0 + (index1-lbound1)*stride1]
-   Obviously this is much slower.  I will make this a compile time option,
-   something like -fsmall-array-offsets.  Mixing code compiled with and without
-   this switch will work.
-
-   (1) This can be worked around by modifying the upper bound of the previous
-   dimension.  This requires extra fields in the descriptor (both real_ubound
-   and fake_ubound).  In tree.def there is mention of TYPE_SEP, which
-   may allow us to do this.  However I can't find mention of this anywhere
-   else.  */
+    data[(index0-lbound0)*stride0 + (index1-lbound1)*stride1]
+   Obviously this is much slower.  I will make this a compile time
+   option, something like -fsmall-array-offsets.  Mixing code compiled
+   with and without this switch will work.
+
+   (1) This can be worked around by modifying the upper bound of the
+   previous dimension.  This requires extra fields in the descriptor
+   (both real_ubound and fake_ubound).  */
 
 
 /* Returns true if the array sym does not require a descriptor.  */