fortran: Ignore unused args in scalarization [PR97896]

The KIND argument of the INDEX intrinsic is a compile time constant
that is used at compile time only to resolve to a kind-specific library
function.  That argument is otherwise completely ignored at runtime, and there is
no code generated for it as the library procedure has no kind argument.
This confuses the scalarizer which expects to see every argument
of elemental functions used when calling a procedure.
This change removes the argument from the scalarization lists
at the beginning of the scalarization process, so that the argument
is completely ignored.
This also reverts the existing workaround
(commit d09847357b965a2c2cda063827ce362d4c9c86f2 except for its testcase).

	PR fortran/97896

gcc/fortran/ChangeLog:
	* intrinsic.c (add_sym_4ind): Remove.
	(add_functions): Use add_sym4 instead of add_sym4ind.
	Don’t special case the index intrinsic.
	* iresolve.c (gfc_resolve_index_func): Use the individual arguments
	directly instead of the full argument list.
	* intrinsic.h (gfc_resolve_index_func): Update the declaration
	accordingly.
	* trans-decl.c (gfc_get_extern_function_decl): Don’t modify the
	list of arguments in the case of the index intrinsic.
	* trans-array.h (gfc_get_intrinsic_for_expr,
	gfc_get_proc_ifc_for_expr): New.
	* trans-array.c (gfc_get_intrinsic_for_expr,
	arg_evaluated_for_scalarization): New.
	(gfc_walk_elemental_function_args): Add intrinsic procedure
	as argument.  Count arguments.  Check arg_evaluated_for_scalarization.
	* trans-intrinsic.c (gfc_walk_intrinsic_function): Update call.
	* trans-stmt.c (get_intrinsic_for_code): New.
	(gfc_trans_call): Update call.

gcc/testsuite/ChangeLog:
	* gfortran.dg/index_5.f90: New.

1 files changed, 60 insertions, 1 deletions

diff --git a/gcc/fortran/trans-array.c b/gcc/fortran/trans-array.c
index 5ceb261..7932185 100644
--- a/gcc/fortran/trans-array.c
+++ b/gcc/fortran/trans-array.c
@@ -11460,6 +11460,59 @@ gfc_get_proc_ifc_for_expr (gfc_expr *procedure_ref)
 }
 
 
+/* Given an expression referring to an intrinsic function call,
+   return the intrinsic symbol.  */
+
+gfc_intrinsic_sym *
+gfc_get_intrinsic_for_expr (gfc_expr *call)
+{
+  if (call == NULL)
+    return NULL;
+
+  /* Normal procedure case.  */
+  if (call->expr_type == EXPR_FUNCTION)
+    return call->value.function.isym;
+  else
+    return NULL;
+}
+
+
+/* Indicates whether an argument to an intrinsic function should be used in
+   scalarization.  It is usually the case, except for some intrinsics
+   requiring the value to be constant, and using the value at compile time only.
+   As the value is not used at runtime in those cases, we don’t produce code
+   for it, and it should not be visible to the scalarizer.
+   FUNCTION is the intrinsic function being called, ACTUAL_ARG is the actual
+   argument being examined in that call, and ARG_NUM the index number
+   of ACTUAL_ARG in the list of arguments.
+   The intrinsic procedure’s dummy argument associated with ACTUAL_ARG is
+   identified using the name in ACTUAL_ARG if it is present (that is: if it’s
+   a keyword argument), otherwise using ARG_NUM.  */
+
+static bool
+arg_evaluated_for_scalarization (gfc_intrinsic_sym *function,
+				 gfc_actual_arglist &actual_arg, int arg_num)
+{
+  if (function != NULL)
+    {
+      switch (function->id)
+	{
+	  case GFC_ISYM_INDEX:
+	    if ((actual_arg.name == NULL && arg_num == 3)
+		|| (actual_arg.name != NULL
+		    && strcmp ("kind", actual_arg.name) == 0))
+	      return false;
+	  /* Fallthrough.  */
+
+	  default:
+	    break;
+	}
+    }
+
+  return true;
+}
+
+
 /* Walk the arguments of an elemental function.
    PROC_EXPR is used to check whether an argument is permitted to be absent.  If
    it is NULL, we don't do the check and the argument is assumed to be present.
@@ -11467,6 +11520,7 @@ gfc_get_proc_ifc_for_expr (gfc_expr *procedure_ref)
 
 gfc_ss *
 gfc_walk_elemental_function_args (gfc_ss * ss, gfc_actual_arglist *arg,
+				  gfc_intrinsic_sym *intrinsic_sym,
 				  gfc_symbol *proc_ifc, gfc_ss_type type)
 {
   gfc_formal_arglist *dummy_arg;
@@ -11483,10 +11537,13 @@ gfc_walk_elemental_function_args (gfc_ss * ss, gfc_actual_arglist *arg,
   else
     dummy_arg = NULL;
 
+  int arg_num = 0;
   scalar = 1;
   for (; arg; arg = arg->next)
     {
-      if (!arg->expr || arg->expr->expr_type == EXPR_NULL)
+      if (!arg->expr
+	  || arg->expr->expr_type == EXPR_NULL
+	  || !arg_evaluated_for_scalarization (intrinsic_sym, *arg, arg_num))
 	goto loop_continue;
 
       newss = gfc_walk_subexpr (head, arg->expr);
@@ -11519,6 +11576,7 @@ gfc_walk_elemental_function_args (gfc_ss * ss, gfc_actual_arglist *arg,
         }
 
 loop_continue:
+      arg_num++;
       if (dummy_arg != NULL)
 	dummy_arg = dummy_arg->next;
     }
@@ -11579,6 +11637,7 @@ gfc_walk_function_expr (gfc_ss * ss, gfc_expr * expr)
 
       ss = gfc_walk_elemental_function_args (old_ss,
 					     expr->value.function.actual,
+					     gfc_get_intrinsic_for_expr (expr),
 					     gfc_get_proc_ifc_for_expr (expr),
 					     GFC_SS_REFERENCE);
       if (ss != old_ss