[gcc(refs/users/mikael/heads/refactor_descriptor_v205.01)] fortran: array descriptor: Move unallocated library result init [PR122521]

https://gcc.gnu.org/g:17a14375fc52193405c2f5bd13ab51bb6ed72bb0

commit 17a14375fc52193405c2f5bd13ab51bb6ed72bb0
Author: Mikael Morin <[email protected]>
Date:   Sun Aug 2 11:07:08 2026 +0200

    fortran: array descriptor: Move unallocated library result init [PR122521]
    
    When the result of a non-inlined intrinsic function is used in a
    reallocating assignment, a fresh unallocated array descriptor is created
    for passing as function result to the library function, rather than using
    the left hand side variable descriptor.  Move the code that creates that
    fresh descriptor to its own function in trans-descriptor.cc.
    
            PR fortran/122521
    
    gcc/fortran/ChangeLog:
    
            * trans-expr.cc (fcncall_realloc_result): Move descriptor
            creation and initialization...
            * trans-descriptor.cc
            (gfc_create_unallocated_library_result_descriptor): ... here as a
            new function.
            * trans-descriptor.h
            (gfc_create_unallocated_library_result_descriptor): New declaration.

Diff:
---
 gcc/fortran/trans-descriptor.cc | 31 +++++++++++++++++++++++++++++++
 gcc/fortran/trans-descriptor.h  |  2 ++
 gcc/fortran/trans-expr.cc       | 11 ++---------
 3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/gcc/fortran/trans-descriptor.cc b/gcc/fortran/trans-descriptor.cc
index aab7310265ab..85a9471bcf1d 100644
--- a/gcc/fortran/trans-descriptor.cc
+++ b/gcc/fortran/trans-descriptor.cc
@@ -774,6 +774,37 @@ gfc_init_descriptor_variable (stmtblock_t *block, gfc_symbol *sym, tree descr)
 }
 
 
+/* Create a fresh array descriptor copied from SOURCE_DESCR, with a cleared data
+   pointer and a possibly different dtype value.  Set the dtype field to DTYPE
+   if different from NULL_TREE; otherwise set it with a default value built
+   using SOURCE_DESCR's type.  Add the copying code and any other initialization
+   to BLOCK and return the descriptor declaration.
+
+   The descriptor created by this function is used to pass to intrinsic
+   functions from the library, when the result is assigned to a reallocatable
+   variable.  The left hand side variable descriptor is not passed directly to
+   the library, and the unallocated descriptor this function creates is passed
+   instead.  Allocation happens in the library; deallocation of the left hand
+   side variable data, if any, and correct bounds mapping happen outside the
+   library, after the function returns.  */
+
+tree
+gfc_create_unallocated_library_result_descriptor (stmtblock_t *block,
+						  tree source_descr, tree dtype)
+{
+  /* Unallocated, the descriptor does not have a dtype.  */
+  if (dtype == NULL_TREE)
+    dtype = gfc_get_dtype (TREE_TYPE (source_descr));
+
+  gfc_conv_descriptor_dtype_set (block, source_descr, dtype);
+
+  tree res_desc = gfc_evaluate_now (source_descr, block);
+  gfc_conv_descriptor_data_set (block, res_desc, null_pointer_node);
+
+  return res_desc;
+}
+
+
 /* For an array descriptor, get the total number of elements.  This is just
    the product of the extents along from_dim to to_dim.  */
 
diff --git a/gcc/fortran/trans-descriptor.h b/gcc/fortran/trans-descriptor.h
index e9006a229716..80f5db72d842 100644
--- a/gcc/fortran/trans-descriptor.h
+++ b/gcc/fortran/trans-descriptor.h
@@ -68,6 +68,8 @@ void gfc_init_result_descriptor (stmtblock_t *block, tree descr);
 void gfc_init_absent_descriptor (stmtblock_t *block, tree descr);
 void gfc_init_descriptor_variable (stmtblock_t *block, gfc_symbol *sym,
 				   tree descr);
+tree gfc_create_unallocated_library_result_descriptor (stmtblock_t *, tree,
+						       tree);
 
 tree gfc_conv_descriptor_size (tree, int);
 tree gfc_conv_descriptor_cosize (tree, int, int);
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 406189af1571..59ce9c64ad89 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -12200,15 +12200,8 @@ fcncall_realloc_result (gfc_se *se, int rank, tree dtype)
   if (POINTER_TYPE_P (TREE_TYPE (desc)))
     desc = build_fold_indirect_ref_loc (input_location, desc);
 
-  /* Unallocated, the descriptor does not have a dtype.  */
-  if (dtype != NULL_TREE)
-    gfc_conv_descriptor_dtype_set (&se->pre, desc, dtype);
-  else
-    gfc_conv_descriptor_dtype_set (&se->pre, desc,
-				   gfc_get_dtype (TREE_TYPE (desc)));
-
-  res_desc = gfc_evaluate_now (desc, &se->pre);
-  gfc_conv_descriptor_data_set (&se->pre, res_desc, null_pointer_node);
+  res_desc = gfc_create_unallocated_library_result_descriptor (&se->pre, desc,
+							       dtype);
   se->expr = gfc_build_addr_expr (NULL_TREE, res_desc);
 
   /* Free the lhs after the function call and copy the result data to