Add an expr::operation_up to struct expression

This adds an expr::operation_up to struct expression, and then
modifies various parts of GDB to use this member when it is non-null.
The list of such spots was a bit surprising to me, and found only
after writing most of the code and then noticing what no longer
compiled.

In a few spots, new accessor methods are added to operation
subclasses, so that code that dissects an expression will work with
the new scheme.

After this change, code that constructs an expression can be switched
to the new form without breaking.

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

	* ada-exp.h (class ada_var_value_operation) <get_symbol>: Remove;
	now in superclass.
	* value.h (fetch_subexp_value): Add "op" parameter.
	* value.c (init_if_undefined_command): Update.
	* tracepoint.c (validate_actionline, encode_actions_1): Update.
	* stap-probe.c (stap_probe::compile_to_ax): Update.
	* printcmd.c (set_command): Update.
	* ppc-linux-nat.c (ppc_linux_nat_target::check_condition):
	Update.
	* parser-defs.h (struct expr_builder) <set_operation>: New
	method.
	* parse.c (parse_exp_in_context, exp_uses_objfile): Update.
	* expression.h (struct expression) <first_opcode>: Update.
	<op>: New member.
	* expprint.c (dump_raw_expression, dump_prefix_expression):
	Update.
	* expop.h (class var_value_operation) <get_symbol>: New method.
	(class register_operation) <get_name>: New method.
	(class equal_operation): No longer a typedef, now a subclass.
	(class unop_memval_operation) <get_type>: New method.
	(class assign_operation) <get_lhs>: New method.
	(class unop_cast_operation) <get_type>: New method.
	* eval.c (evaluate_expression, evaluate_type)
	(evaluate_subexpression_type): Update.
	(fetch_subexp_value): Add "op" parameter.
	(parse_and_eval_type): Update.
	* dtrace-probe.c (dtrace_probe::compile_to_ax): Update.
	* breakpoint.c (update_watchpoint, watchpoint_check)
	(watchpoint_exp_is_const, watch_command_1): Update.
	* ax-gdb.c (gen_trace_for_expr, gen_eval_for_expr, gen_printf):
	Update.

1 files changed, 25 insertions, 5 deletions

diff --git a/gdb/eval.c b/gdb/eval.c
index f1302ef..142d4ae 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -120,8 +120,14 @@ expression::evaluate (struct type *expect_type, enum noside noside)
       && !thread_stack_temporaries_enabled_p (inferior_thread ()))
     stack_temporaries.emplace (inferior_thread ());
 
-  int pos = 0;
-  struct value *retval = evaluate_subexp (expect_type, this, &pos, noside);
+  struct value *retval;
+  if (op != nullptr)
+    retval = op->evaluate (expect_type, this, noside);
+  else
+    {
+      int pos = 0;
+      retval = evaluate_subexp (expect_type, this, &pos, noside);
+    }
 
   if (stack_temporaries.has_value ()
       && value_in_thread_stack_temporaries (retval, inferior_thread ()))
@@ -153,6 +159,8 @@ evaluate_type (struct expression *exp)
 struct value *
 evaluate_subexpression_type (struct expression *exp, int subexp)
 {
+  if (exp->op != nullptr)
+    return exp->op->evaluate (nullptr, exp, EVAL_AVOID_SIDE_EFFECTS);
   return evaluate_subexp (nullptr, exp, &subexp, EVAL_AVOID_SIDE_EFFECTS);
 }
 
@@ -179,8 +187,9 @@ evaluate_subexpression_type (struct expression *exp, int subexp)
    values will be left on the value chain.  */
 
 void
-fetch_subexp_value (struct expression *exp, int *pc, struct value **valp,
-		    struct value **resultp,
+fetch_subexp_value (struct expression *exp, int *pc,
+		    expr::operation *op,
+		    struct value **valp, struct value **resultp,
 		    std::vector<value_ref_ptr> *val_chain,
 		    bool preserve_errors)
 {
@@ -198,7 +207,10 @@ fetch_subexp_value (struct expression *exp, int *pc, struct value **valp,
 
   try
     {
-      result = evaluate_subexp (nullptr, exp, pc, EVAL_NORMAL);
+      if (op == nullptr)
+	result = evaluate_subexp (nullptr, exp, pc, EVAL_NORMAL);
+      else
+	result = op->evaluate (nullptr, exp, EVAL_NORMAL);
     }
   catch (const gdb_exception &ex)
     {
@@ -4491,5 +4503,13 @@ parse_and_eval_type (const char *p, int length)
   expression_up expr = parse_expression (tmp);
   if (expr->first_opcode () != UNOP_CAST)
     error (_("Internal error in eval_type."));
+
+  if (expr->op != nullptr)
+    {
+      expr::unop_cast_operation *op
+	= dynamic_cast<expr::unop_cast_operation *> (expr->op.get ());
+      return op->get_type ();
+    }
+
   return expr->elts[1].type;
 }