Introduce unop_addr_operation

This adds class unop_addr_operation, which implements UNOP_ADDR.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* expop.h (class unop_addr_operation): New.
	* ax-gdb.c (gen_expr_unop) <case UNOP_ADDR>: New.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
+	* expop.h (class unop_addr_operation): New.
+	* ax-gdb.c (gen_expr_unop) <case UNOP_ADDR>: New.
+
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
 	* expop.h (class typeid_operation): New.

gdb/ax-gdb.c

@@ -2744,6 +2744,11 @@ gen_expr_unop (struct expression *exp,
       gen_deref (value);
       break;
 
+    case UNOP_ADDR:
+      lhs->generate_ax (exp, ax, value);
+      gen_address_of (value);
+      break;
+
     default:
       gdb_assert_not_reached ("invalid case in gen_expr_unop");
     }

gdb/expop.h

@@ -1546,6 +1546,42 @@ class typeid_operation
   { return OP_TYPEID; }
 };
 
+/* Implement the address-of operation.  */
+class unop_addr_operation
+  : public maybe_constant_operation<operation_up>
+{
+public:
+
+  using maybe_constant_operation::maybe_constant_operation;
+
+  value *evaluate (struct type *expect_type,
+		   struct expression *exp,
+		   enum noside noside) override
+  {
+    /* C++: check for and handle pointer to members.  */
+    if (noside == EVAL_SKIP)
+      return eval_skip_value (exp);
+    else
+      return std::get<0> (m_storage)->evaluate_for_address (exp, noside);
+  }
+
+  enum exp_opcode opcode () const override
+  { return UNOP_ADDR; }
+
+protected:
+
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override
+  {
+    gen_expr_unop (exp, UNOP_ADDR,
+		   std::get<0> (this->m_storage).get (),
+		   ax, value);
+  }
+};
+
 } /* namespace expr */
 
 #endif /* EXPOP_H */