https://gcc.gnu.org/g:8c7924c0e3ad450e98ae2081dce8fa2a9916479d
commit 8c7924c0e3ad450e98ae2081dce8fa2a9916479d
Author: Mikael Morin <mik...@gcc.gnu.org>
Date: Wed Jul 9 21:18:18 2025 +0200
fortran: Factor array descriptor references
Save parts of array descriptor references to a variable so that all the
expressions using the descriptor as base object benefit from the
simplified reference.
gcc/fortran/ChangeLog:
* trans-array.cc (gfc_conv_ss_descriptor): Move the descriptor
reference initialisation...
(set_factored_descriptor_value): ... to this new function. Walk
the reference passed as arguments and try to simplify some of it
to a variable.
Diff:
---
gcc/fortran/trans-array.cc | 79 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 78 insertions(+), 1 deletion(-)
diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index 52888c1e1f1b..51ec1c78a28c 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -3437,6 +3437,83 @@ save_descriptor_data (tree descr, tree data)
}
+/* Save the descriptor reference VALUE to storage pointed by DESC_PTR. As
there
+ may be a lot of code using subreferences of the descriptor, try to factor
+ them by evaluating the leading part of the data reference to a variable,
+ adding extra code to BLOCK.
+
+ To avoid copying large amounts of data we only save pointers in the
reference
+ chain, and as late in the chain as possible. */
+
+void
+set_factored_descriptor_value (stmtblock_t *block, tree *desc_ptr, tree value)
+{
+ /* As the reference is processed from last to first, statements will be
+ generate in reversed order, so can't be put directly in BLOCK. We use
+ TMP_BLOCK instead. */
+ stmtblock_t tmp_block;
+ tree accumulated_code = NULL_TREE;
+
+ gfc_init_block (&tmp_block);
+
+ tree *ptr_ref = nullptr;
+
+ tree data_ref = value;
+ bool seen_component = false;
+ while (true)
+ {
+ if (TREE_CODE (data_ref) == INDIRECT_REF)
+ {
+ /* If there is no component reference after the pointer dereference in
+ the reference chain, the pointer can't be saved to a variable as
+ it may be a pointer or allocatable, and we have to keep the parent
+ reference to be able to update the pointer value. Otherwise the
+ pointer can be saved to a variable. */
+ if (seen_component)
+ {
+ /* Don't evaluate the pointer to a variable yet; do it only if the
+ variable would be significantly more simple than the reference
+ it replaces. That is if the reference contains anything
+ different from a NOP, a COMPONENT or a DECL. */
+ ptr_ref = &TREE_OPERAND (data_ref, 0);
+ }
+
+ data_ref = TREE_OPERAND (data_ref, 0);
+ }
+ else if (TREE_CODE (data_ref) == COMPONENT_REF)
+ {
+ seen_component = true;
+ data_ref = TREE_OPERAND (data_ref, 0);
+ }
+ else if (TREE_CODE (data_ref) == NOP_EXPR)
+ data_ref = TREE_OPERAND (data_ref, 0);
+ else
+ {
+ if (DECL_P (data_ref))
+ break;
+
+ if (ptr_ref != nullptr)
+ {
+ /* We have seen a pointer before, and its reference appears to be
+ worth saving. Do it now. */
+ tree ptr = *ptr_ref;
+ *ptr_ref = gfc_evaluate_now (ptr, &tmp_block);
+ gfc_add_expr_to_block (&tmp_block, accumulated_code);
+ accumulated_code = gfc_finish_block (&tmp_block);
+ }
+
+ if (TREE_CODE (data_ref) == ARRAY_REF)
+ data_ref = TREE_OPERAND (data_ref, 0);
+ else
+ break;
+ }
+ }
+
+ *desc_ptr = value;
+ gfc_add_expr_to_block (block, accumulated_code);
+}
+
+
/* Translate expressions for the descriptor and data pointer of a SS. */
/*GCC ARRAYS*/
@@ -3457,7 +3534,7 @@ gfc_conv_ss_descriptor (stmtblock_t * block, gfc_ss * ss,
int base)
se.descriptor_only = 1;
gfc_conv_expr_lhs (&se, ss_info->expr);
gfc_add_block_to_block (block, &se.pre);
- info->descriptor = se.expr;
+ set_factored_descriptor_value (block, &info->descriptor, se.expr);
ss_info->string_length = se.string_length;
ss_info->class_container = se.class_container;
