From 55bdbff857f80da9e3464968f1ada2be3484fcf9 Mon Sep 17 00:00:00 2001
From: Tom Tromey <tom@tromey.com>
Date: Mon, 8 Mar 2021 07:27:57 -0700
Subject: [PATCH] Introduce register_operation

This adds class register_operation, which implements OP_REGISTER.

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

	* expop.h (class register_operation): New.
	* eval.c (eval_op_register): No longer static.
	* ax-gdb.c (register_operation::do_generate_ax): New method.
---
 gdb/ChangeLog |  6 ++++++
 gdb/ax-gdb.c  | 24 ++++++++++++++++++++++++
 gdb/eval.c    |  2 +-
 gdb/expop.h   | 30 ++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b237cade176..0633260cb5a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
+	* expop.h (class register_operation): New.
+	* eval.c (eval_op_register): No longer static.
+	* ax-gdb.c (register_operation::do_generate_ax): New method.
+
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
 	* expop.h (class last_operation): New.
diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 60281700703..5ffe5a00da1 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2341,6 +2341,30 @@ var_msym_value_operation::do_generate_ax (struct expression *exp,
     }
 }
 
+void
+register_operation::do_generate_ax (struct expression *exp,
+				    struct agent_expr *ax,
+				    struct axs_value *value,
+				    struct type *cast_type)
+{
+  const char *name = std::get<0> (m_storage).c_str ();
+  int len = std::get<0> (m_storage).size ();
+  int reg;
+
+  reg = user_reg_map_name_to_regnum (ax->gdbarch, name, len);
+  if (reg == -1)
+    internal_error (__FILE__, __LINE__,
+		    _("Register $%s not available"), name);
+  /* No support for tracing user registers yet.  */
+  if (reg >= gdbarch_num_cooked_regs (ax->gdbarch))
+    error (_("'%s' is a user-register; "
+	     "GDB cannot yet trace user-register contents."),
+	   name);
+  value->kind = axs_lvalue_register;
+  value->u.reg = reg;
+  value->type = register_type (ax->gdbarch, reg);
+}
+
 }
 
 /* This handles the middle-to-right-side of code generation for binary
diff --git a/gdb/eval.c b/gdb/eval.c
index 56010ee22e9..4601c92ed5f 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -1254,7 +1254,7 @@ eval_op_func_static_var (struct type *expect_type, struct expression *exp,
 
 /* Helper function that implements the body of OP_REGISTER.  */
 
-static struct value *
+struct value *
 eval_op_register (struct type *expect_type, struct expression *exp,
 		  enum noside noside, const char *name)
 {
diff --git a/gdb/expop.h b/gdb/expop.h
index 73b66bf154b..a0e00302532 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -58,6 +58,9 @@ extern struct value *eval_op_func_static_var (struct type *expect_type,
 					      struct expression *exp,
 					      enum noside noside,
 					      value *func, const char *var);
+extern struct value *eval_op_register (struct type *expect_type,
+				       struct expression *exp,
+				       enum noside noside, const char *name);
 
 namespace expr
 {
@@ -597,6 +600,33 @@ public:
   { return OP_LAST; }
 };
 
+class register_operation
+  : public tuple_holding_operation<std::string>
+{
+public:
+
+  using tuple_holding_operation::tuple_holding_operation;
+
+  value *evaluate (struct type *expect_type,
+		   struct expression *exp,
+		   enum noside noside) override
+  {
+    return eval_op_register (expect_type, exp, noside,
+			     std::get<0> (m_storage).c_str ());
+  }
+
+  enum exp_opcode opcode () const override
+  { return OP_REGISTER; }
+
+protected:
+
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override;
+};
+
 } /* namespace expr */
 
 #endif /* EXPOP_H */
-- 
2.30.2