[PATCH 13/24] gdb: add value::allocate_register

[Simon Marchi <simon.marchi@polymtl.ca>]

From: Simon Marchi <simon.marchi@efficios.com>

Add value::allocate_register, to facilitate allocating a value
representing a register in a given frame (or rather, in the given
frame's previous frame).  It will be used in a subsequent patch.  I
changed one relatively obvious spot that could use it, to at least
exercise the code path.

Change-Id: Icd4960f5e471a74b657bb3596c88d89679ef3772
---
 gdb/regcache.c |  7 ++-----
 gdb/value.c    | 15 +++++++++++++++
 gdb/value.h    |  7 +++++++
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/gdb/regcache.c b/gdb/regcache.c
index 4f3881386f34..4256b82da19a 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -792,11 +792,8 @@ readable_regcache::cooked_read_value (int regnum)
       || (m_has_pseudo && m_register_status[regnum] != REG_UNKNOWN)
       || !gdbarch_pseudo_register_read_value_p (m_descr->gdbarch))
     {
-      struct value *result;
-
-      result = value::allocate (register_type (m_descr->gdbarch, regnum));
-      result->set_lval (lval_register);
-      VALUE_REGNUM (result) = regnum;
+      value *result = value::allocate_register
+	(get_next_frame_sentinel_okay (get_current_frame ()), regnum);
 
       /* It is more efficient in general to do this delegation in this
 	 direction than in the other one, even though the value-based
diff --git a/gdb/value.c b/gdb/value.c
index 17b7c53d0522..a1b18087416f 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -959,6 +959,21 @@ value::allocate (struct type *type)
   return allocate (type, true);
 }
 
+/* See value.h  */
+
+struct value *
+value::allocate_register (frame_info_ptr next_frame, int regnum)
+{
+  value *result
+    = value::allocate (register_type (frame_unwind_arch (next_frame), regnum));
+
+  result->set_lval (lval_register);
+  VALUE_REGNUM (result) = regnum;
+  VALUE_NEXT_FRAME_ID (result) = get_frame_id (next_frame);
+
+  return result;
+}
+
 /* Allocate a  value  that has the correct length
    for COUNT repetitions of type TYPE.  */
 
diff --git a/gdb/value.h b/gdb/value.h
index 37017c9dd9f7..511bde8bbd46 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -159,6 +159,13 @@ struct value
   /* Allocate a value and its contents for type TYPE.  */
   static struct value *allocate (struct type *type);
 
+  /* Allocate a non-lazy value representing register RENUM in the frame previous
+     to NEXT_FRAME.  The type of the value is found using `register_type`.
+
+     The caller is responsible for filling the value's contents.  */
+  static struct value *allocate_register (frame_info_ptr next_frame,
+					  int regnum);
+
   /* Create a computed lvalue, with type TYPE, function pointers
      FUNCS, and closure CLOSURE.  */
   static struct value *allocate_computed (struct type *type,
-- 
2.42.1