[1/2] Implement some agent expressions for Ada

diff --git a/gdb/ada-exp.h b/gdb/ada-exp.h
index 36ac3aaddb7..409cac4668f 100644
--- a/gdb/ada-exp.h
+++ b/gdb/ada-exp.h
@@ -130,6 +130,14 @@  class ada_wrapped_operation
 
   enum exp_opcode opcode () const override
   { return std::get<0> (m_storage)->opcode (); }
+
+protected:
+
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override;
 };
 
 /* An Ada string constant.  */
@@ -255,6 +263,18 @@  class ada_binop_equal_operation
 			    arg1, arg2);
   }
 
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override
+  {
+    gen_expr_binop (exp, opcode (),
+		    std::get<1> (this->m_storage).get (),
+		    std::get<2> (this->m_storage).get (),
+		    ax, value);
+  }
+
   enum exp_opcode opcode () const override
   { return std::get<0> (m_storage); }
 };
@@ -380,7 +400,11 @@  class ada_var_value_operation
 
 protected:
 
-  using operation::do_generate_ax;
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override;
 };
 
 /* Variant of var_msym_value_operation for Ada.  */
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 40f85914a56..ce5faef40a4 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -60,6 +60,7 @@ 
 #include <algorithm>
 #include "ada-exp.h"
 #include "charset.h"
+#include "ax-gdb.h"
 
 /* Define whether or not the C operator '/' truncates towards zero for
    differently signed operands (truncation direction is undefined in C).
@@ -9207,6 +9208,23 @@  ada_enum_name (const char *name)
     }
 }
 
+/* If TYPE is a dynamic type, return the base type.  Otherwise, if
+   there is no parallel type, return nullptr.  */
+
+static struct type *
+find_base_type (struct type *type)
+{
+  struct type *raw_real_type
+    = ada_check_typedef (ada_get_base_type (type));
+
+  /* No parallel XVS or XVE type.  */
+  if (type == raw_real_type
+      && ada_find_parallel_type (type, "___XVE") == nullptr)
+    return nullptr;
+
+  return raw_real_type;
+}
+
 /* If VAL is wrapped in an aligner or subtype wrapper, return the
    value it wraps.  */
 
@@ -9227,13 +9245,8 @@  unwrap_value (struct value *val)
     }
   else
     {
-      struct type *raw_real_type =
-	ada_check_typedef (ada_get_base_type (type));
-
-      /* If there is no parallel XVS or XVE type, then the value is
-	 already unwrapped.  Return it without further modification.  */
-      if ((type == raw_real_type)
-	  && ada_find_parallel_type (type, "___XVE") == NULL)
+      struct type *raw_real_type = find_base_type (type);
+      if (raw_real_type == nullptr)
 	return val;
 
       return
@@ -10659,6 +10672,21 @@  ada_wrapped_operation::evaluate (struct type *expect_type,
   return result;
 }
 
+void
+ada_wrapped_operation::do_generate_ax (struct expression *exp,
+				       struct agent_expr *ax,
+				       struct axs_value *value,
+				       struct type *cast_type)
+{
+  std::get<0> (m_storage)->generate_ax (exp, ax, value, cast_type);
+
+  struct type *type = value->type;
+  if (ada_is_aligner_type (type))
+    error (_("Aligner types cannot be handled in agent expressions"));
+  else if (find_base_type (type) != nullptr)
+    error (_("Dynamic types cannot be handled in agent expressions"));
+}
+
 value *
 ada_string_operation::evaluate (struct type *expect_type,
 				struct expression *exp,
@@ -11009,6 +11037,33 @@  ada_var_value_operation::resolve (struct expression *exp,
   return false;
 }
 
+void
+ada_var_value_operation::do_generate_ax (struct expression *exp,
+					 struct agent_expr *ax,
+					 struct axs_value *value,
+					 struct type *cast_type)
+{
+  symbol *sym = std::get<0> (m_storage).symbol;
+
+  if (sym->domain () == UNDEF_DOMAIN)
+    error (_("Unexpected unresolved symbol, %s, during evaluation"),
+	   sym->print_name ());
+
+  struct type *type = static_unwrap_type (sym->type ());
+  if (ada_is_tagged_type (type, 0)
+      || (type->code () == TYPE_CODE_REF
+	  && ada_is_tagged_type (type->target_type (), 0)))
+    error (_("Tagged types cannot be handled in agent expressions"));
+
+  if ((type->code () == TYPE_CODE_STRUCT
+       && dynamic_template_type (type) != NULL)
+      || (type->code () == TYPE_CODE_UNION
+	  && ada_find_parallel_type (type, "___XVU") != NULL))
+    error (_("Dynamic types cannot be handled in agent expressions"));
+
+  var_value_operation::do_generate_ax (exp, ax, value, cast_type);
+}
+
 value *
 ada_atr_val_operation::evaluate (struct type *expect_type,
 				 struct expression *exp,
diff --git a/gdb/testsuite/gdb.ada/ax-ada.exp b/gdb/testsuite/gdb.ada/ax-ada.exp
new file mode 100644
index 00000000000..b08f7c4362c
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/ax-ada.exp
@@ -0,0 +1,31 @@ 
+# Copyright 2019-2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+standard_ada_testfile prog
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "START" ${testdir}/prog.adb]
+runto "prog.adb:$bp_location"
+
+gdb_test "maint agent-eval variable = 23" ".*end"
diff --git a/gdb/testsuite/gdb.ada/ax-ada/prog.adb b/gdb/testsuite/gdb.ada/ax-ada/prog.adb
new file mode 100644
index 00000000000..3852711e88c
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/ax-ada/prog.adb
@@ -0,0 +1,20 @@ 
+--  Copyright 2023 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+procedure Prog is
+   Variable : Integer := 23;
+begin
+   null; -- START
+end Prog;