[linemap PATCH] Constify lookup

[Nathan Sidwell <nathan at acm dot org>]

looking up a line map takes a non-constant line_maps object, which is 
confusing.

This makes the caching fields mutable, so permits a constant object, as 
one might expect for a lookup.

The linemaps_info_{ordinary,macro} structures are crying out to be 
templatized, but that kind of turns into a rathole cleaning up the C-era 
accessors and like.  I punted.

committing to trunk

nathan
--
Nathan Sidwell

2019-10-15  Nathan Sidwell  <nathan@acm.org>

	* include/line-map.h (struct maps_info_ordinary): Make cache
	mutable.
	(struct maps_info_macro): Likewise.
	(LINEMAPS_CACHE): Remove non-ref accessor. Constify ref accessor.
	(LINEMAPS_ORDINARY_CACHE, LINEMAPS_MACRO_CACHE): Likewise.
	(LINEMAPS_ORDINARY_MAP_AT, LINEMAPS_MACRO_MAP_AT): Use
	LINEMAPS_USED and LINEMAPS_MAP_AT.
	(linemap_lookup): Constify line_map arg.
	linemap.c (linemap_ordinary_map_lookup, linemap_macro_map_lookup):
	Constify line_map arg.

Index: include/line-map.h
===================================================================
--- include/line-map.h	(revision 276991)
+++ include/line-map.h	(working copy)
@@ -725,5 +725,5 @@ struct GTY(()) maps_info_ordinary {
   unsigned int used;
 
-  unsigned int cache;
+  mutable unsigned int cache;
 };
 
@@ -740,5 +740,5 @@ struct GTY(()) maps_info_macro {
   unsigned int used;
 
-  unsigned int cache;
+  mutable unsigned int cache;
 };
 
@@ -866,17 +866,6 @@ LINEMAPS_USED (line_maps *set, bool map_
    linemap_lookup. MAP_KIND shall be TRUE if we are interested in
    macro maps, FALSE otherwise.  */
-inline unsigned int
-LINEMAPS_CACHE (const line_maps *set, bool map_kind)
-{
-  if (map_kind)
-    return set->info_macro.cache;
-  else
-    return set->info_ordinary.cache;
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_CACHE (line_maps *set, bool map_kind)
+LINEMAPS_CACHE (const line_maps *set, bool map_kind)
 {
   if (map_kind)
@@ -928,7 +917,7 @@ inline line_map_ordinary *
 LINEMAPS_ORDINARY_MAP_AT (const line_maps *set, int index)
 {
-  linemap_assert (index >= 0);
-  linemap_assert ((unsigned int)index < set->info_ordinary.used);
-  return &set->info_ordinary.maps[index];
+  linemap_assert (index >= 0
+		  && (unsigned int)index < LINEMAPS_USED (set, false));
+  return (line_map_ordinary *)LINEMAPS_MAP_AT (set, false, index);
 }
 
@@ -950,14 +939,6 @@ LINEMAPS_ORDINARY_USED (const line_maps
 /* Return the index of the last ordinary map that was looked up with
    linemap_lookup.  */
-inline unsigned int
-LINEMAPS_ORDINARY_CACHE (const line_maps *set)
-{
-  return LINEMAPS_CACHE (set, false);
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_ORDINARY_CACHE (line_maps *set)
+LINEMAPS_ORDINARY_CACHE (const line_maps *set)
 {
   return LINEMAPS_CACHE (set, false);
@@ -992,7 +973,7 @@ inline line_map_macro *
 LINEMAPS_MACRO_MAP_AT (const line_maps *set, int index)
 {
-  linemap_assert (index >= 0);
-  linemap_assert ((unsigned int)index < set->info_macro.used);
-  return &set->info_macro.maps[index];
+  linemap_assert (index >= 0
+		  && (unsigned int)index < LINEMAPS_USED (set, true));
+  return (line_map_macro *)LINEMAPS_MAP_AT (set, true, index);
 }
 
@@ -1012,16 +993,8 @@ LINEMAPS_MACRO_USED (const line_maps *se
 }
 
-/* Returns the index of the last macro map looked up with
+/* Return the index of the last macro map that was looked up with
    linemap_lookup.  */
-inline unsigned int
-LINEMAPS_MACRO_CACHE (const line_maps *set)
-{
-  return LINEMAPS_CACHE (set, true);
-}
-
-/* As above, but by reference (e.g. as an lvalue).  */
-
 inline unsigned int &
-LINEMAPS_MACRO_CACHE (line_maps *set)
+LINEMAPS_MACRO_CACHE (const line_maps *set)
 {
   return LINEMAPS_CACHE (set, true);
@@ -1131,5 +1104,5 @@ extern const line_map *linemap_add
    function returns NULL.  */
 extern const line_map *linemap_lookup
-  (class line_maps *, location_t);
+  (const line_maps *, location_t);
 
 /* Returns TRUE if the line table set tracks token locations across
Index: line-map.c
===================================================================
--- line-map.c	(revision 276991)
+++ line-map.c	(working copy)
@@ -28,7 +28,7 @@ along with this program; see the file CO
 
 static void trace_include (const line_maps *, const line_map_ordinary *);
-static const line_map_ordinary * linemap_ordinary_map_lookup (line_maps *,
+static const line_map_ordinary * linemap_ordinary_map_lookup (const line_maps *,
 							      location_t);
-static const line_map_macro* linemap_macro_map_lookup (line_maps *,
+static const line_map_macro* linemap_macro_map_lookup (const line_maps *,
 						       location_t);
 static location_t linemap_macro_map_loc_to_def_point
@@ -938,5 +938,5 @@ linemap_position_for_loc_and_offset (lin
 
 const struct line_map*
-linemap_lookup (line_maps *set, location_t line)
+linemap_lookup (const line_maps *set, location_t line)
 {
   if (IS_ADHOC_LOC (line))
@@ -953,5 +953,5 @@ linemap_lookup (line_maps *set, location
 
 static const line_map_ordinary *
-linemap_ordinary_map_lookup (line_maps *set, location_t line)
+linemap_ordinary_map_lookup (const line_maps *set, location_t line)
 {
   unsigned int md, mn, mx;
@@ -966,5 +966,5 @@ linemap_ordinary_map_lookup (line_maps *
   mn = LINEMAPS_ORDINARY_CACHE (set);
   mx = LINEMAPS_ORDINARY_USED (set);
-  
+
   cached = LINEMAPS_ORDINARY_MAP_AT (set, mn);
   /* We should get a segfault if no line_maps have been added yet.  */
@@ -1001,5 +1001,5 @@ linemap_ordinary_map_lookup (line_maps *
 
 static const line_map_macro *
-linemap_macro_map_lookup (line_maps *set, location_t line)
+linemap_macro_map_lookup (const line_maps *set, location_t line)
 {
   unsigned int md, mn, mx;