re PR c++/55135 (Segfault of gcc on a big file)

gcc/
	PR c++/55135
	* except.h (remove_unreachable_eh_regions): New prototype.
	* except.c (remove_eh_handler_splicer): New function, split out
	of remove_eh_handler.
	(remove_eh_handler): Use remove_eh_handler_splicer.  Add comment
	warning about running it on many EH regions one at a time.
	(remove_unreachable_eh_regions_worker): New function, walk the
	EH tree in depth-first order and remove non-marked regions.
	(remove_unreachable_eh_regions): New function.
	* tree-eh.c (mark_reachable_handlers): New function, split out
	from remove_unreachable_handlers.
	(remove_unreachable_handlers): Use mark_reachable_handlers and
	remove_unreachable_eh_regions.
	(remove_unreachable_handlers_no_lp): Use mark_reachable_handlers
	and remove_unreachable_eh_regions.

From-SVN: r196464

1 files changed, 60 insertions, 11 deletions

diff --git a/gcc/except.c b/gcc/except.c
index 3e424eb..4e85f73 100644
--- a/gcc/except.c
+++ b/gcc/except.c
@@ -1505,12 +1505,12 @@ remove_eh_landing_pad (eh_landing_pad lp)
   (*cfun->eh->lp_array)[lp->index] = NULL;
 }
 
-/* Splice REGION from the region tree.  */
+/* Splice the EH region at PP from the region tree.  */
 
-void
-remove_eh_handler (eh_region region)
+static void
+remove_eh_handler_splicer (eh_region *pp)
 {
-  eh_region *pp, *pp_start, p, outer;
+  eh_region region = *pp;
   eh_landing_pad lp;
 
   for (lp = region->landing_pads; lp ; lp = lp->next_lp)
@@ -1520,15 +1520,11 @@ remove_eh_handler (eh_region region)
       (*cfun->eh->lp_array)[lp->index] = NULL;
     }
 
-  outer = region->outer;
-  if (outer)
-    pp_start = &outer->inner;
-  else
-    pp_start = &cfun->eh->region_tree;
-  for (pp = pp_start, p = *pp; p != region; pp = &p->next_peer, p = *pp)
-    continue;
   if (region->inner)
     {
+      eh_region p, outer;
+      outer = region->outer;
+
       *pp = p = region->inner;
       do
 	{
@@ -1543,6 +1539,59 @@ remove_eh_handler (eh_region region)
   (*cfun->eh->region_array)[region->index] = NULL;
 }
 
+/* Splice a single EH region REGION from the region tree.
+
+   To unlink REGION, we need to find the pointer to it with a relatively
+   expensive search in REGION's outer region.  If you are going to
+   remove a number of handlers, using remove_unreachable_eh_regions may
+   be a better option.  */
+
+void
+remove_eh_handler (eh_region region)
+{
+  eh_region *pp, *pp_start, p, outer;
+
+  outer = region->outer;
+  if (outer)
+    pp_start = &outer->inner;
+  else
+    pp_start = &cfun->eh->region_tree;
+  for (pp = pp_start, p = *pp; p != region; pp = &p->next_peer, p = *pp)
+    continue;
+
+  remove_eh_handler_splicer (pp);
+}
+
+/* Worker for remove_unreachable_eh_regions.
+   PP is a pointer to the region to start a region tree depth-first
+   search from.  R_REACHABLE is the set of regions that have to be
+   preserved.  */
+
+static void
+remove_unreachable_eh_regions_worker (eh_region *pp, sbitmap r_reachable)
+{
+  while (*pp)
+    {
+      eh_region region = *pp;
+      remove_unreachable_eh_regions_worker (&region->inner, r_reachable);
+      if (!bitmap_bit_p (r_reachable, region->index))
+	remove_eh_handler_splicer (pp);
+      else
+	pp = &region->next_peer;
+    }
+}
+
+/* Splice all EH regions *not* marked in R_REACHABLE from the region tree.
+   Do this by traversing the EH tree top-down and splice out regions that
+   are not marked.  By removing regions from the leaves, we avoid costly
+   searches in the region tree.  */
+
+void
+remove_unreachable_eh_regions (sbitmap r_reachable)
+{
+  remove_unreachable_eh_regions_worker (&cfun->eh->region_tree, r_reachable);
+}
+
 /* Invokes CALLBACK for every exception handler landing pad label.
    Only used by reload hackery; should not be used by new code.  */