Don't maintain a warning spec for 'UNKNOWN_LOCATION'/'BUILTINS_LOCATION' [PR101574]

This resolves PR101574 "gcc/sparseset.h:215:20: error: suggest parentheses
around assignment used as truth value [-Werror=parentheses]", as (bogusly)
reported at commit a61f6afbee370785cf091fe46e2e022748528307:

    In file included from [...]/source-gcc/gcc/lra-lives.c:43:
    [...]/source-gcc/gcc/lra-lives.c: In function ‘void make_hard_regno_dead(int)’:
    [...]/source-gcc/gcc/sparseset.h:215:20: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
      215 |        && (((ITER) = sparseset_iter_elm (SPARSESET)) || 1);             \
          |            ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    [...]/source-gcc/gcc/lra-lives.c:304:3: note: in expansion of macro ‘EXECUTE_IF_SET_IN_SPARSESET’
      304 |   EXECUTE_IF_SET_IN_SPARSESET (pseudos_live, i)
          |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~

	gcc/
	PR bootstrap/101574
	* diagnostic-spec.c (warning_suppressed_at, copy_warning): Handle
	'RESERVED_LOCATION_P' locations.
	* warning-control.cc (get_nowarn_spec, suppress_warning)
	(copy_warning): Likewise.

2 files changed, 50 insertions, 20 deletions

diff --git a/gcc/diagnostic-spec.c b/gcc/diagnostic-spec.c
index eac5a33..85ffb72 100644
--- a/gcc/diagnostic-spec.c
+++ b/gcc/diagnostic-spec.c
@@ -115,6 +115,8 @@ GTY(()) xint_hash_map_t *nowarn_map;
 bool
 warning_suppressed_at (location_t loc, opt_code opt /* = all_warnings */)
 {
+  gcc_checking_assert (!RESERVED_LOCATION_P (loc));
+
   if (!nowarn_map)
     return false;
 
@@ -137,6 +139,8 @@ bool
 suppress_warning_at (location_t loc, opt_code opt /* = all_warnings */,
 		     bool supp /* = true */)
 {
+  gcc_checking_assert (!RESERVED_LOCATION_P (loc));
+
   const nowarn_spec_t optspec (supp ? opt : opt_code ());
 
   if (nowarn_spec_t *pspec = nowarn_map ? nowarn_map->get (loc) : NULL)
@@ -173,8 +177,20 @@ copy_warning (location_t to, location_t from)
   if (!nowarn_map)
     return;
 
-  if (nowarn_spec_t *pspec = nowarn_map->get (from))
-    nowarn_map->put (to, *pspec);
+  nowarn_spec_t *from_spec;
+  if (RESERVED_LOCATION_P (from))
+    from_spec = NULL;
+  else
+    from_spec = nowarn_map->get (from);
+  if (RESERVED_LOCATION_P (to))
+    /* We cannot set no-warning dispositions for 'to', so we have no chance but
+       lose those potentially set for 'from'.  */
+    ;
   else
-    nowarn_map->remove (to);
+    {
+      if (from_spec)
+	nowarn_map->put (to, *from_spec);
+      else
+	nowarn_map->remove (to);
+    }
 }
diff --git a/gcc/warning-control.cc b/gcc/warning-control.cc
index 8d6c082..36a47ab 100644
--- a/gcc/warning-control.cc
+++ b/gcc/warning-control.cc
@@ -89,7 +89,7 @@ get_nowarn_spec (const_tree expr)
 {
   const location_t loc = get_location (expr);
 
-  if (loc == UNKNOWN_LOCATION)
+  if (RESERVED_LOCATION_P (loc))
     return NULL;
 
   if (!get_no_warning_bit (expr))
@@ -105,6 +105,9 @@ get_nowarn_spec (const gimple *stmt)
 {
   const location_t loc = get_location (stmt);
 
+  if (RESERVED_LOCATION_P (loc))
+    return NULL;
+
   if (!get_no_warning_bit (stmt))
     return NULL;
 
@@ -158,7 +161,8 @@ suppress_warning (tree expr, opt_code opt /* = all_warnings */,
 
   const location_t loc = get_location (expr);
 
-  supp = suppress_warning_at (loc, opt, supp) || supp;
+  if (!RESERVED_LOCATION_P (loc))
+    supp = suppress_warning_at (loc, opt, supp) || supp;
   set_no_warning_bit (expr, supp);
 }
 
@@ -174,7 +178,8 @@ suppress_warning (gimple *stmt, opt_code opt /* = all_warnings */,
 
   const location_t loc = get_location (stmt);
 
-  supp = suppress_warning_at (loc, opt, supp) || supp;
+  if (!RESERVED_LOCATION_P (loc))
+    supp = suppress_warning_at (loc, opt, supp) || supp;
   set_no_warning_bit (stmt, supp);
 }
 
@@ -186,24 +191,33 @@ void copy_warning (ToType to, FromType from)
 {
   const location_t to_loc = get_location (to);
 
-  if (nowarn_spec_t *from_map = get_nowarn_spec (from))
-    {
-      /* If there's an entry in the map the no-warning bit must be set.  */
-      gcc_assert (get_no_warning_bit (from));
+  bool supp = get_no_warning_bit (from);
 
-      gcc_checking_assert (nowarn_map);
-      nowarn_map->put (to_loc, *from_map);
-      set_no_warning_bit (to, true);
-    }
+  nowarn_spec_t *from_spec = get_nowarn_spec (from);
+  if (RESERVED_LOCATION_P (to_loc))
+    /* We cannot set no-warning dispositions for 'to', so we have no chance but
+       lose those potentially set for 'from'.  */
+    ;
   else
     {
-      if (nowarn_map)
-	nowarn_map->remove (to_loc);
-
-      /* The no-warning bit might be set even if there's no entry
-	 in the map.  */
-      set_no_warning_bit (to, get_no_warning_bit (from));
+      if (from_spec)
+	{
+	  /* If there's an entry in the map the no-warning bit must be set.  */
+	  gcc_assert (supp);
+
+	  gcc_checking_assert (nowarn_map);
+	  nowarn_map->put (to_loc, *from_spec);
+	}
+      else
+	{
+	  if (nowarn_map)
+	    nowarn_map->remove (to_loc);
+	}
     }
+
+  /* The no-warning bit might be set even if the map has not been consulted, or
+     otherwise if there's no entry in the map.  */
+  set_no_warning_bit (to, supp);
 }
 
 /* Copy the warning disposition mapping from one expression to another.  */