2 files changed, 95 insertions, 2 deletions

diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index bd36a6c..7f2bcf2 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -831,6 +831,22 @@ dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
 }
 
 
+/* Custom function data object for architecture specific prev_register
+   implementation.  Main purpose of this object is to allow caching of
+   expensive data lookups in the prev_register handling.  */
+
+struct dwarf2_frame_fn_data
+{
+  /* The cookie to identify the custom function data by.  */
+  fn_prev_register cookie;
+
+  /* The custom function data.  */
+  void *data;
+
+  /* Pointer to the next custom function data object for this frame.  */
+  struct dwarf2_frame_fn_data *next;
+};
+
 struct dwarf2_frame_cache
 {
   /* DWARF Call Frame Address.  */
@@ -862,6 +878,8 @@ struct dwarf2_frame_cache
      dwarf2_tailcall_frame_unwind unwinder so this field does not apply for
      them.  */
   void *tailcall_cache;
+
+  struct dwarf2_frame_fn_data *fn_data;
 };
 
 static struct dwarf2_frame_cache *
@@ -1221,6 +1239,48 @@ dwarf2_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
     }
 }
 
+/* See frame.h.  */
+
+void *
+dwarf2_frame_get_fn_data (frame_info_ptr this_frame, void **this_cache,
+			  fn_prev_register cookie)
+{
+  struct dwarf2_frame_fn_data *fn_data = nullptr;
+  struct dwarf2_frame_cache *cache
+    = dwarf2_frame_cache (this_frame, this_cache);
+
+  /* Find the object for the function.  */
+  for (fn_data = cache->fn_data; fn_data; fn_data = fn_data->next)
+    if (fn_data->cookie == cookie)
+      return fn_data->data;
+
+  return nullptr;
+}
+
+/* See frame.h.  */
+
+void *
+dwarf2_frame_allocate_fn_data (frame_info_ptr this_frame, void **this_cache,
+			       fn_prev_register cookie, unsigned long size)
+{
+  struct dwarf2_frame_fn_data *fn_data = nullptr;
+  struct dwarf2_frame_cache *cache
+    = dwarf2_frame_cache (this_frame, this_cache);
+
+  /* First try to find an existing object.  */
+  void *data = dwarf2_frame_get_fn_data (this_frame, this_cache, cookie);
+  gdb_assert (data == nullptr);
+
+  /* No object found, lets create a new instance.  */
+  fn_data = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_fn_data);
+  fn_data->cookie = cookie;
+  fn_data->data = frame_obstack_zalloc (size);
+  fn_data->next = cache->fn_data;
+  cache->fn_data = fn_data;
+
+  return fn_data->data;
+}
+
 /* Proxy for tailcall_frame_dealloc_cache for bottom frame of a virtual tail
    call frames chain.  */
 
diff --git a/gdb/dwarf2/frame.h b/gdb/dwarf2/frame.h
index 4444c15..5643e55 100644
--- a/gdb/dwarf2/frame.h
+++ b/gdb/dwarf2/frame.h
@@ -66,6 +66,9 @@ enum dwarf2_frame_reg_rule
 
 /* Register state.  */
 
+typedef struct value *(*fn_prev_register) (frame_info_ptr this_frame,
+					   void **this_cache, int regnum);
+
 struct dwarf2_frame_state_reg
 {
   /* Each register save state can be described in terms of a CFA slot,
@@ -78,8 +81,7 @@ struct dwarf2_frame_state_reg
       const gdb_byte *start;
       ULONGEST len;
     } exp;
-    struct value *(*fn) (frame_info_ptr this_frame, void **this_cache,
-			 int regnum);
+    fn_prev_register fn;
   } loc;
   enum dwarf2_frame_reg_rule how;
 };
@@ -262,4 +264,35 @@ extern int dwarf2_fetch_cfa_info (struct gdbarch *gdbarch, CORE_ADDR pc,
 				  const gdb_byte **cfa_start_out,
 				  const gdb_byte **cfa_end_out);
 
+
+/* Allocate a new instance of the function unique data.
+
+   The main purpose of this custom function data object is to allow caching the
+   value of expensive lookups in the prev_register implementation.
+
+   THIS_FRAME is the frame that the custom data object should be associated
+   with.
+   THIS_CACHE is the dwarf2 cache object to store the pointer on.
+   COOKIE is the key for the prev_function implementation.
+   SIZE is the size of the custom data object to allocate.  */
+
+extern void *dwarf2_frame_allocate_fn_data (frame_info_ptr this_frame,
+					    void **this_cache,
+					    fn_prev_register cookie,
+					    unsigned long size);
+
+/* Retrieve the function unique data for this frame or NULL if none exists.
+
+   The main purpose of this custom function data object is to allow caching the
+   value of expensive lookups in the prev_register implementation.
+
+   THIS_FRAME is the frame that the custom data object should be associated
+   with.
+   THIS_CACHE is the dwarf2 cache object to store the pointer on.
+   COOKIE is the key for the prev_function implementation.  */
+
+extern void *dwarf2_frame_get_fn_data (frame_info_ptr this_frame,
+				       void **this_cache,
+				       fn_prev_register cookie);
+
 #endif /* dwarf2-frame.h */