[Ada] Fix debug info glitches for character indexes

[Eric Botcazou]

This is another regression in the debug info, this time introduced on the 
mainline by my patch toggling the signedness of Character in Ada.

Tested on x86_64-suse-linux, applied on the mainline.


2016-02-16  Eric Botcazou  <ebotca...@adacore.com>

        * gcc-interface/gigi.h (maybe_debug_type): New inline function.
        * gcc-interface/misc.c (gnat_get_array_descr_info): Use it.
        Call maybe_character_value on the array bounds.  Get to the base type
        of the index type and call maybe_debug_type on it.
        * gcc-interface/utils.c (finish_character_type): Add special treatment
        for char_type_node.

-- 
Eric Botcazou
Index: gcc-interface/gigi.h
===================================================================
--- gcc-interface/gigi.h	(revision 233448)
+++ gcc-interface/gigi.h	(working copy)
@@ -1164,3 +1164,14 @@ maybe_character_value (tree expr)
 
   return expr;
 }
+
+/* Return the debug type of TYPE if it exists, otherwise TYPE itself.  */
+
+static inline tree
+maybe_debug_type (tree type)
+{
+  if (TYPE_CAN_HAVE_DEBUG_TYPE_P (type) && TYPE_DEBUG_TYPE (type))
+    type = TYPE_DEBUG_TYPE (type);
+
+  return type;
+}
Index: gcc-interface/misc.c
===================================================================
--- gcc-interface/misc.c	(revision 233467)
+++ gcc-interface/misc.c	(working copy)
@@ -786,8 +786,7 @@ gnat_get_array_descr_info (const_tree co
   tree thinptr_bound_field = NULL_TREE;
 
   /* ??? See gnat_get_debug_type.  */
-  if (TYPE_CAN_HAVE_DEBUG_TYPE_P (type) && TYPE_DEBUG_TYPE (type))
-    type = TYPE_DEBUG_TYPE (type);
+  type = maybe_debug_type (type);
 
   /* If we have an implementation type for a packed array, get the orignial
      array type.  */
@@ -944,8 +943,10 @@ gnat_get_array_descr_info (const_tree co
 	    }
 	  else
 	    {
-	      info->dimen[i].lower_bound = TYPE_MIN_VALUE (index_type);
-	      info->dimen[i].upper_bound = TYPE_MAX_VALUE (index_type);
+	      info->dimen[i].lower_bound
+		= maybe_character_value (TYPE_MIN_VALUE (index_type));
+	      info->dimen[i].upper_bound
+		= maybe_character_value (TYPE_MAX_VALUE (index_type));
 	    }
 	}
 
@@ -963,13 +964,12 @@ gnat_get_array_descr_info (const_tree co
 	  thinptr_bound_field = DECL_CHAIN (thinptr_bound_field);
 	}
 
-      /* The DWARF back-end will output exactly INDEX_TYPE as the array index'
-	 "root" type, so pell subtypes when possible.  */
-      while (TREE_TYPE (index_type)
-	     && !subrange_type_for_debug_p (index_type, NULL, NULL))
+      /* The DWARF back-end will output BOUNDS_TYPE as the base type of
+	 the array index, so get to the base type of INDEX_TYPE.  */
+      while (TREE_TYPE (index_type))
 	index_type = TREE_TYPE (index_type);
 
-      info->dimen[i].bounds_type = index_type;
+      info->dimen[i].bounds_type = maybe_debug_type (index_type);
       info->dimen[i].stride = NULL_TREE;
     }
 
Index: gcc-interface/utils.c
===================================================================
--- gcc-interface/utils.c	(revision 233448)
+++ gcc-interface/utils.c	(working copy)
@@ -1625,8 +1625,11 @@ finish_character_type (tree char_type)
   if (TYPE_UNSIGNED (char_type))
     return;
 
-  /* Make a copy of the unsigned version since we'll modify it below.  */
-  tree unsigned_char_type = copy_type (gnat_unsigned_type_for (char_type));
+  /* Make a copy of a generic unsigned version since we'll modify it.  */
+  tree unsigned_char_type
+    = (char_type == char_type_node
+       ? unsigned_char_type_node
+       : copy_type (gnat_unsigned_type_for (char_type)));
 
   TYPE_NAME (unsigned_char_type) = TYPE_NAME (char_type);
   TYPE_STRING_FLAG (unsigned_char_type) = TYPE_STRING_FLAG (char_type);