preprocessor: line-map tidying

Message ID 5b9e5121-f75b-fd2e-2e9d-30575ca136d8@fb.com
State New
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Series
  • preprocessor: line-map tidying
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Commit Message

Ian Lance Taylor via Gcc-patches July 20, 2020, 12:12 p.m.
I found the linemap logic dealing with running out of column numbers 
confusing.  There's no need for completely separate code blocks there, 
as we can rely on the masking operations working all the way down to 
zero bits.  The two binary searches for linemap lookups could do with 
modernization of placing the var decls at their initialization point. 
(These two searches work in opposite directions, and while lower_bound 
would work there, the caching got in the way and I decided to be 
conservative.)

             libcpp/
             * line-map.c (linemap_add): Simplify column overflow 
calculation.
             Add comment about range and column bit init.
             (linemap_ordinary_map_lookup): Refactor for RAII
             (linemap_macro_map_lookup): Likewise.

pushed
-- 
Nathan Sidwell : Facebook

Patch

diff --git i/libcpp/line-map.c w/libcpp/line-map.c
index 8a390d0857b..a8d52861dee 100644
--- i/libcpp/line-map.c
+++ w/libcpp/line-map.c
@@ -462,17 +462,12 @@  linemap_add (line_maps *set, enum lc_reason reason,
 {
   /* Generate a start_location above the current highest_location.
      If possible, make the low range bits be zero.  */
-  location_t start_location;
-  if (set->highest_location < LINE_MAP_MAX_LOCATION_WITH_COLS)
-    {
-      start_location = set->highest_location + (1 << set->default_range_bits);
-      if (set->default_range_bits)
-	start_location &= ~((1 << set->default_range_bits) - 1);
-      linemap_assert (0 == (start_location
-			    & ((1 << set->default_range_bits) - 1)));
-    }
-  else
-    start_location = set->highest_location + 1;
+  location_t start_location = set->highest_location + 1;
+  unsigned range_bits = 0;
+  if (start_location < LINE_MAP_MAX_LOCATION_WITH_COLS)
+    range_bits = set->default_range_bits;
+  start_location += (1 << range_bits) - 1;
+  start_location &=  ~((1 << range_bits) - 1);
 
   linemap_assert (!LINEMAPS_ORDINARY_USED (set)
 		  || (start_location
@@ -537,8 +532,9 @@  linemap_add (line_maps *set, enum lc_reason reason,
   map->to_file = to_file;
   map->to_line = to_line;
   LINEMAPS_ORDINARY_CACHE (set) = LINEMAPS_ORDINARY_USED (set) - 1;
-  map->m_column_and_range_bits = 0;
-  map->m_range_bits = 0;
+  /* Do not store range_bits here.  That's readjusted in
+     linemap_line_start.  */
+  map->m_range_bits = map->m_column_and_range_bits = 0;
   set->highest_location = start_location;
   set->highest_line = start_location;
   set->max_column_hint = 0;
@@ -954,19 +950,16 @@  linemap_lookup (const line_maps *set, location_t line)
 static const line_map_ordinary *
 linemap_ordinary_map_lookup (const line_maps *set, location_t line)
 {
-  unsigned int md, mn, mx;
-  const line_map_ordinary *cached, *result;
-
   if (IS_ADHOC_LOC (line))
     line = get_location_from_adhoc_loc (set, line);
 
   if (set ==  NULL || line < RESERVED_LOCATION_COUNT)
     return NULL;
 
-  mn = LINEMAPS_ORDINARY_CACHE (set);
-  mx = LINEMAPS_ORDINARY_USED (set);
+  unsigned mn = LINEMAPS_ORDINARY_CACHE (set);
+  unsigned mx = LINEMAPS_ORDINARY_USED (set);
 
-  cached = LINEMAPS_ORDINARY_MAP_AT (set, mn);
+  const line_map_ordinary *cached = LINEMAPS_ORDINARY_MAP_AT (set, mn);
   /* We should get a segfault if no line_maps have been added yet.  */
   if (line >= MAP_START_LOCATION (cached))
     {
@@ -981,7 +974,7 @@  linemap_ordinary_map_lookup (const line_maps *set, location_t line)
 
   while (mx - mn > 1)
     {
-      md = (mn + mx) / 2;
+      unsigned md = (mn + mx) / 2;
       if (MAP_START_LOCATION (LINEMAPS_ORDINARY_MAP_AT (set, md)) > line)
 	mx = md;
       else
@@ -989,7 +982,7 @@  linemap_ordinary_map_lookup (const line_maps *set, location_t line)
     }
 
   LINEMAPS_ORDINARY_CACHE (set) = mn;
-  result = LINEMAPS_ORDINARY_MAP_AT (set, mn);
+  const line_map_ordinary *result = LINEMAPS_ORDINARY_MAP_AT (set, mn);
   linemap_assert (line >= MAP_START_LOCATION (result));
   return result;
 }
@@ -1002,21 +995,18 @@  linemap_ordinary_map_lookup (const line_maps *set, location_t line)
 static const line_map_macro *
 linemap_macro_map_lookup (const line_maps *set, location_t line)
 {
-  unsigned int md, mn, mx;
-  const struct line_map_macro *cached, *result;
-
   if (IS_ADHOC_LOC (line))
     line = get_location_from_adhoc_loc (set, line);
 
   linemap_assert (line >= LINEMAPS_MACRO_LOWEST_LOCATION (set));
 
-  if (set ==  NULL)
+  if (set == NULL)
     return NULL;
 
-  mn = LINEMAPS_MACRO_CACHE (set);
-  mx = LINEMAPS_MACRO_USED (set);
-  cached = LINEMAPS_MACRO_MAP_AT (set, mn);
-  
+  unsigned mn = LINEMAPS_MACRO_CACHE (set);
+  unsigned mx = LINEMAPS_MACRO_USED (set);
+  const struct line_map_macro *cached = LINEMAPS_MACRO_MAP_AT (set, mn);
+
   if (line >= MAP_START_LOCATION (cached))
     {
       if (mn == 0 || line < MAP_START_LOCATION (&cached[-1]))
@@ -1027,7 +1017,7 @@  linemap_macro_map_lookup (const line_maps *set, location_t line)
 
   while (mn < mx)
     {
-      md = (mx + mn) / 2;
+      unsigned md = (mx + mn) / 2;
       if (MAP_START_LOCATION (LINEMAPS_MACRO_MAP_AT (set, md)) > line)
 	mn = md + 1;
       else
@@ -1035,7 +1025,7 @@  linemap_macro_map_lookup (const line_maps *set, location_t line)
     }
 
   LINEMAPS_MACRO_CACHE (set) = mx;
-  result = LINEMAPS_MACRO_MAP_AT (set, LINEMAPS_MACRO_CACHE (set));
+  const struct line_map_macro *result = LINEMAPS_MACRO_MAP_AT (set, mx);
   linemap_assert (MAP_START_LOCATION (result) <= line);
 
   return result;