Introduce unop_alignof_operation

This adds class unop_alignof_operation, which implements UNOP_ALIGNOF.

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

	* expop.h (class unop_alignof_operation): New.
	* eval.c (eval_op_alignof): No longer static.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
+	* expop.h (class unop_alignof_operation): New.
+	* eval.c (eval_op_alignof): No longer static.
+
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
 	* expop.h (class unop_sizeof_operation): New.

gdb/eval.c

@@ -1881,7 +1881,7 @@ eval_op_ind (struct type *expect_type, struct expression *exp,
 
 /* A helper function for UNOP_ALIGNOF.  */
 
-static struct value *
+struct value *
 eval_op_alignof (struct type *expect_type, struct expression *exp,
 		 enum noside noside,
 		 struct value *arg1)

gdb/expop.h

@@ -189,6 +189,10 @@ extern struct value *eval_op_ind (struct type *expect_type,
 extern struct value *eval_op_type (struct type *expect_type,
 				   struct expression *exp,
 				   enum noside noside, struct type *type);
+extern struct value *eval_op_alignof (struct type *expect_type,
+				      struct expression *exp,
+				      enum noside noside,
+				      struct value *arg1);
 
 namespace expr
 {
@@ -1611,6 +1615,27 @@ protected:
     override;
 };
 
+/* Implement 'alignof'.  */
+class unop_alignof_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
+  {
+    value *val = std::get<0> (m_storage)->evaluate (nullptr, exp,
+						    EVAL_AVOID_SIDE_EFFECTS);
+    return eval_op_alignof (expect_type, exp, noside, val);
+  }
+
+  enum exp_opcode opcode () const override
+  { return UNOP_ALIGNOF; }
+};
+
 } /* namespace expr */
 
 #endif /* EXPOP_H */