[Patch, Fortran] 2/3 Refactor locations where _vptr is (re)set.

[Patch, Fortran] 2/3 Refactor locations where _vptr is (re)set.

[Andre Vehreschild]

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Hi all,

this patch refactors most of the locations where the _vptr of a class data type
is reset. The code was inconsistent in most of the locations. The goal of using
only one routine for setting the _vptr is to be able to later modify it more
easily.

The ultimate goal being that every time one assigns to a class data type a
consistent way is used to prevent forgetting the corner cases. So this is just a
small step in this direction. I think it is worth to simplify the code to
something consistent to reduce maintenance efforts anyhow.

Regtested ok on x86_64 Fedora 39. Ok for mainline?

Regards,
	Andre
--
Andre Vehreschild * Email: vehre ad gmx dot de

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From f9018fa7d4dc752331e62963c9cf86ab01a1bfc5 Mon Sep 17 00:00:00 2001
From: Andre Vehreschild <vehre@gcc.gnu.org>
Date: Fri, 7 Jun 2024 08:57:36 +0200
Subject: [PATCH 2/3] Use gfc_reset_vptr more consistently.

The vptr for a class type is set in various ways in different
locations.  Refactor the use and simplify code.

gcc/fortran/ChangeLog:

	* trans-array.cc (structure_alloc_comps): Use reset_vptr.
	* trans-decl.cc (gfc_trans_deferred_vars): Same.
	(gfc_generate_function_code): Same.
	* trans-expr.cc (gfc_reset_vptr): Allow supplying the class
	type.
	(gfc_conv_procedure_call): Use reset_vptr.
	* trans-intrinsic.cc (gfc_conv_intrinsic_transfer): Same.
---
 gcc/fortran/trans-array.cc     | 34 ++++----------------
 gcc/fortran/trans-decl.cc      | 19 ++----------
 gcc/fortran/trans-expr.cc      | 57 +++++++++++++++++-----------------
 gcc/fortran/trans-intrinsic.cc | 10 +-----
 4 files changed, 38 insertions(+), 82 deletions(-)

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index cc50b961a97..b3088a892c8 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -9864,15 +9864,7 @@ structure_alloc_comps (gfc_symbol * der_type, tree decl, tree dest,
 	      else
 		{
 		  /* Build the vtable address and set the vptr with it.  */
-		  tree vtab;
-		  gfc_symbol *vtable;
-		  vtable = gfc_find_derived_vtab (c->ts.u.derived);
-		  vtab = vtable->backend_decl;
-		  if (vtab == NULL_TREE)
-		    vtab = gfc_get_symbol_decl (vtable);
-		  vtab = gfc_build_addr_expr (NULL, vtab);
-		  vtab = fold_convert (TREE_TYPE (tmp), vtab);
-		  gfc_add_modify (&tmpblock, tmp, vtab);
+		  gfc_reset_vptr (&tmpblock, nullptr, tmp, c->ts.u.derived);
 		}
 	    }

@@ -9903,15 +9895,13 @@ structure_alloc_comps (gfc_symbol * der_type, tree decl, tree dest,
 	      && (CLASS_DATA (c)->attr.allocatable
 		  || CLASS_DATA (c)->attr.class_pointer))
 	    {
-	      tree vptr_decl;
+	      tree class_ref;

 	      /* Allocatable CLASS components.  */
-	      comp = fold_build3_loc (input_location, COMPONENT_REF, ctype,
-				      decl, cdecl, NULL_TREE);
-
-	      vptr_decl = gfc_class_vptr_get (comp);
+	      class_ref = fold_build3_loc (input_location, COMPONENT_REF, ctype,
+					   decl, cdecl, NULL_TREE);

-	      comp = gfc_class_data_get (comp);
+	      comp = gfc_class_data_get (class_ref);
 	      if (GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (comp)))
 		gfc_conv_descriptor_data_set (&fnblock, comp,
 					      null_pointer_node);
@@ -9926,19 +9916,7 @@ structure_alloc_comps (gfc_symbol * der_type, tree decl, tree dest,
 	      /* The dynamic type of a disassociated pointer or unallocated
 		 allocatable variable is its declared type. An unlimited
 		 polymorphic entity has no declared type.  */
-	      if (!UNLIMITED_POLY (c))
-		{
-		  vtab = gfc_find_derived_vtab (c->ts.u.derived);
-		  if (!vtab->backend_decl)
-		     gfc_get_symbol_decl (vtab);
-		  tmp = gfc_build_addr_expr (NULL_TREE, vtab->backend_decl);
-		}
-	      else
-		tmp = build_int_cst (TREE_TYPE (vptr_decl), 0);
-
-	      tmp = fold_build2_loc (input_location, MODIFY_EXPR,
-					 void_type_node, vptr_decl, tmp);
-	      gfc_add_expr_to_block (&fnblock, tmp);
+	      gfc_reset_vptr (&fnblock, nullptr, class_ref, c->ts.u.derived);

 	      cmp_has_alloc_comps = false;
 	    }
diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index 88538713a02..1786f80245f 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -5070,26 +5070,11 @@ gfc_trans_deferred_vars (gfc_symbol * proc_sym, gfc_wrapped_block * block)
 	      if (sym->ts.type == BT_CLASS)
 		{
 		  /* Initialize _vptr to declared type.  */
-		  gfc_symbol *vtab;
-		  tree rhs;
-
 		  gfc_save_backend_locus (&loc);
 		  gfc_set_backend_locus (&sym->declared_at);
 		  e = gfc_lval_expr_from_sym (sym);
-		  gfc_add_vptr_component (e);
-		  gfc_init_se (&se, NULL);
-		  se.want_pointer = 1;
-		  gfc_conv_expr (&se, e);
+		  gfc_reset_vptr (&init, e);
 		  gfc_free_expr (e);
-		  if (UNLIMITED_POLY (sym))
-		    rhs = build_int_cst (TREE_TYPE (se.expr), 0);
-		  else
-		    {
-		      vtab = gfc_find_derived_vtab (sym->ts.u.derived);
-		      rhs = gfc_build_addr_expr (TREE_TYPE (se.expr),
-						gfc_get_symbol_decl (vtab));
-		    }
-		  gfc_add_modify (&init, se.expr, rhs);
 		  gfc_restore_backend_locus (&loc);
 		}

@@ -7931,7 +7916,7 @@ gfc_generate_function_code (gfc_namespace * ns)
 			      fold_convert (TREE_TYPE (tmp),
 					    null_pointer_node));
 	      gfc_reset_vptr (&init, nullptr, result,
-			      CLASS_DATA (sym->result)->ts.u.derived);
+			      sym->result->ts.u.derived);
 	    }
 	  else if (sym->ts.type == BT_DERIVED
 		   && !sym->attr.allocatable)
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 558a7380516..454b87581f5 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -532,12 +532,12 @@ gfc_find_and_cut_at_last_class_ref (gfc_expr *e, bool is_mold,

 /* Reset the vptr to the declared type, e.g. after deallocation.
    Use the variable in CLASS_CONTAINER if available.  Otherwise, recreate
-   one with e or derived.  At least one of the two has to be set.  The generated
-   assignment code is added at the end of BLOCK.  */
+   one with e or class_type.  At least one of the two has to be set.  The
+   generated assignment code is added at the end of BLOCK.  */

 void
 gfc_reset_vptr (stmtblock_t *block, gfc_expr *e, tree class_container,
-		gfc_symbol *derived)
+		gfc_symbol *class_type)
 {
   tree vptr = NULL_TREE;

@@ -564,15 +564,31 @@ gfc_reset_vptr (stmtblock_t *block, gfc_expr *e, tree class_container,
   if (vptr == NULL_TREE)
     return;

-  if (UNLIMITED_POLY (e))
+  if (UNLIMITED_POLY (e)
+      || UNLIMITED_POLY (class_type)
+      /* When the class_type's source is not a symbol (e.g. a component's ts),
+	 then look at the _data-components type.  */
+      || (class_type != NULL && class_type->ts.type == BT_UNKNOWN
+	  && class_type->components && class_type->components->ts.u.derived
+	  && class_type->components->ts.u.derived->attr.unlimited_polymorphic))
     gfc_add_modify (block, vptr, build_int_cst (TREE_TYPE (vptr), 0));
   else
     {
-      gfc_symbol *vtab;
+      gfc_symbol *vtab, *type = nullptr;
       tree vtable;

+      if (e)
+	type = e->ts.u.derived;
+      else if (class_type)
+	{
+	  if (class_type->ts.type == BT_CLASS)
+	    type = CLASS_DATA (class_type)->ts.u.derived;
+	  else
+	    type = class_type;
+	}
+      gcc_assert (type);
       /* Return the vptr to the address of the declared type.  */
-      vtab = gfc_find_derived_vtab (derived ? derived : e->ts.u.derived);
+      vtab = gfc_find_derived_vtab (type);
       vtable = vtab->backend_decl;
       if (vtable == NULL_TREE)
 	vtable = gfc_get_symbol_decl (vtab);
@@ -6872,29 +6888,14 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
 							       NULL_TREE, true,
 							       e, e->ts, cls);
 		      gfc_add_expr_to_block (&block, tmp);
-		      tmp = fold_build2_loc (input_location, MODIFY_EXPR,
-					     void_type_node, ptr,
-					     null_pointer_node);
-		      gfc_add_expr_to_block (&block, tmp);
+		      gfc_add_modify (&block, ptr,
+				      fold_convert (TREE_TYPE (ptr),
+						    null_pointer_node));

-		      if (fsym->ts.type == BT_CLASS && UNLIMITED_POLY (fsym))
-			{
-			  gfc_add_modify (&block, ptr,
-					  fold_convert (TREE_TYPE (ptr),
-							null_pointer_node));
-			  gfc_add_expr_to_block (&block, tmp);
-			}
-		      else if (fsym->ts.type == BT_CLASS)
-			{
-			  gfc_symbol *vtab;
-			  vtab = gfc_find_derived_vtab (fsym->ts.u.derived);
-			  tmp = gfc_get_symbol_decl (vtab);
-			  tmp = gfc_build_addr_expr (NULL_TREE, tmp);
-			  ptr = gfc_class_vptr_get (parmse.expr);
-			  gfc_add_modify (&block, ptr,
-					  fold_convert (TREE_TYPE (ptr), tmp));
-			  gfc_add_expr_to_block (&block, tmp);
-			}
+		      if (fsym->ts.type == BT_CLASS)
+			gfc_reset_vptr (&block, nullptr,
+					build_fold_indirect_ref (parmse.expr),
+					fsym->ts.u.derived);

 		      if (fsym->attr.optional
 			  && e->expr_type == EXPR_VARIABLE
diff --git a/gcc/fortran/trans-intrinsic.cc b/gcc/fortran/trans-intrinsic.cc
index 96839705112..ac7fcd250d3 100644
--- a/gcc/fortran/trans-intrinsic.cc
+++ b/gcc/fortran/trans-intrinsic.cc
@@ -8815,15 +8815,7 @@ scalar_transfer:

       /* For CLASS results, set the _vptr.  */
       if (mold_expr->ts.type == BT_CLASS)
-	{
-	  tree vptr;
-	  gfc_symbol *vtab;
-	  vptr = gfc_class_vptr_get (tmpdecl);
-	  vtab = gfc_find_derived_vtab (source_expr->ts.u.derived);
-	  gcc_assert (vtab);
-	  tmp = gfc_build_addr_expr (NULL_TREE, gfc_get_symbol_decl (vtab));
-	  gfc_add_modify (&se->pre, vptr, fold_convert (TREE_TYPE (vptr), tmp));
-	}
+	gfc_reset_vptr (&se->pre, nullptr, tmpdecl, source_expr->ts.u.derived);

       se->expr = tmpdecl;
     }
--
2.45.1