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.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@196464 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 171 insertions, 75 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 06a0ca2b6fe..dbef6b39da2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,21 @@
+2013-03-05  Steven Bosscher  <steven@gcc.gnu.org>
+
+	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.
+
 2013-03-05  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/56525
diff --git a/gcc/except.c b/gcc/except.c
index 3e424eb9d7f..4e85f731837 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.  */
 
diff --git a/gcc/except.h b/gcc/except.h
index 6c202415f83..bc9654a7ae4 100644
--- a/gcc/except.h
+++ b/gcc/except.h
@@ -229,6 +229,7 @@ extern void init_eh_for_function (void);
 
 extern void remove_eh_landing_pad (eh_landing_pad);
 extern void remove_eh_handler (eh_region);
+extern void remove_unreachable_eh_regions (sbitmap);
 
 extern bool current_function_has_exception_handlers (void);
 extern void output_function_exception_table (const char *);
diff --git a/gcc/tree-eh.c b/gcc/tree-eh.c
index 29b4f9a7c71..6b9dac9258e 100644
--- a/gcc/tree-eh.c
+++ b/gcc/tree-eh.c
@@ -3519,22 +3519,37 @@ struct gimple_opt_pass pass_lower_eh_dispatch =
  }
 };
 
-/* Walk statements, see what regions are really referenced and remove
-   those that are unused.  */
+/* Walk statements, see what regions and, optionally, landing pads
+   are really referenced.
+   
+   Returns in R_REACHABLEP an sbitmap with bits set for reachable regions,
+   and in LP_REACHABLE an sbitmap with bits set for reachable landing pads.
+
+   Passing NULL for LP_REACHABLE is valid, in this case only reachable
+   regions are marked.
+
+   The caller is responsible for freeing the returned sbitmaps.  */
 
 static void
-remove_unreachable_handlers (void)
+mark_reachable_handlers (sbitmap *r_reachablep, sbitmap *lp_reachablep)
 {
   sbitmap r_reachable, lp_reachable;
-  eh_region region;
-  eh_landing_pad lp;
   basic_block bb;
-  int lp_nr, r_nr;
+  bool mark_landing_pads = (lp_reachablep != NULL);
+  gcc_checking_assert (r_reachablep != NULL);
 
   r_reachable = sbitmap_alloc (cfun->eh->region_array->length ());
-  lp_reachable = sbitmap_alloc (cfun->eh->lp_array->length ());
   bitmap_clear (r_reachable);
-  bitmap_clear (lp_reachable);
+  *r_reachablep = r_reachable;
+
+  if (mark_landing_pads)
+    {
+      lp_reachable = sbitmap_alloc (cfun->eh->lp_array->length ());
+      bitmap_clear (lp_reachable);
+      *lp_reachablep = lp_reachable;
+    }
+  else
+    lp_reachable = NULL;
 
   FOR_EACH_BB (bb)
     {
@@ -3543,20 +3558,24 @@ remove_unreachable_handlers (void)
       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 	{
 	  gimple stmt = gsi_stmt (gsi);
-	  lp_nr = lookup_stmt_eh_lp (stmt);
 
-	  /* Negative LP numbers are MUST_NOT_THROW regions which
-	     are not considered BB enders.  */
-	  if (lp_nr < 0)
-	    bitmap_set_bit (r_reachable, -lp_nr);
-
-	  /* Positive LP numbers are real landing pads, are are BB enders.  */
-	  else if (lp_nr > 0)
+	  if (mark_landing_pads)
 	    {
-	      gcc_assert (gsi_one_before_end_p (gsi));
-	      region = get_eh_region_from_lp_number (lp_nr);
-	      bitmap_set_bit (r_reachable, region->index);
-	      bitmap_set_bit (lp_reachable, lp_nr);
+	      int lp_nr = lookup_stmt_eh_lp (stmt);
+
+	      /* Negative LP numbers are MUST_NOT_THROW regions which
+		 are not considered BB enders.  */
+	      if (lp_nr < 0)
+		bitmap_set_bit (r_reachable, -lp_nr);
+
+	      /* Positive LP numbers are real landing pads, and BB enders.  */
+	      else if (lp_nr > 0)
+		{
+		  gcc_assert (gsi_one_before_end_p (gsi));
+		  eh_region region = get_eh_region_from_lp_number (lp_nr);
+		  bitmap_set_bit (r_reachable, region->index);
+		  bitmap_set_bit (lp_reachable, lp_nr);
+		}
 	    }
 
 	  /* Avoid removing regions referenced from RESX/EH_DISPATCH.  */
@@ -3573,6 +3592,19 @@ remove_unreachable_handlers (void)
 	    }
 	}
     }
+}
+
+/* Remove unreachable handlers and unreachable landing pads.  */
+
+static void
+remove_unreachable_handlers (void)
+{
+  sbitmap r_reachable, lp_reachable;
+  eh_region region;
+  eh_landing_pad lp;
+  unsigned i;
+
+  mark_reachable_handlers (&r_reachable, &lp_reachable);
 
   if (dump_file)
     {
@@ -3584,21 +3616,24 @@ remove_unreachable_handlers (void)
       dump_bitmap_file (dump_file, lp_reachable);
     }
 
-  for (r_nr = 1;
-       vec_safe_iterate (cfun->eh->region_array, r_nr, &region); ++r_nr)
-    if (region && !bitmap_bit_p (r_reachable, r_nr))
-      {
-	if (dump_file)
-	  fprintf (dump_file, "Removing unreachable region %d\n", r_nr);
-	remove_eh_handler (region);
-      }
+  if (dump_file)
+    {
+      FOR_EACH_VEC_SAFE_ELT (cfun->eh->region_array, i, region)
+	if (region && !bitmap_bit_p (r_reachable, region->index))
+	  fprintf (dump_file,
+		   "Removing unreachable region %d\n",
+		   region->index);
+    }
+
+  remove_unreachable_eh_regions (r_reachable);
 
-  for (lp_nr = 1;
-       vec_safe_iterate (cfun->eh->lp_array, lp_nr, &lp); ++lp_nr)
-    if (lp && !bitmap_bit_p (lp_reachable, lp_nr))
+  FOR_EACH_VEC_SAFE_ELT (cfun->eh->lp_array, i, lp)
+    if (lp && !bitmap_bit_p (lp_reachable, lp->index))
       {
 	if (dump_file)
-	  fprintf (dump_file, "Removing unreachable landing pad %d\n", lp_nr);
+	  fprintf (dump_file,
+		   "Removing unreachable landing pad %d\n",
+		   lp->index);
 	remove_eh_landing_pad (lp);
       }
 
@@ -3624,12 +3659,12 @@ void
 maybe_remove_unreachable_handlers (void)
 {
   eh_landing_pad lp;
-  int i;
+  unsigned i;
 
   if (cfun->eh == NULL)
     return;
-              
-  for (i = 1; vec_safe_iterate (cfun->eh->lp_array, i, &lp); ++i)
+           
+  FOR_EACH_VEC_SAFE_ELT (cfun->eh->lp_array, i, lp)
     if (lp && lp->post_landing_pad)
       {
 	if (label_to_block (lp->post_landing_pad) == NULL)
@@ -3642,45 +3677,38 @@ maybe_remove_unreachable_handlers (void)
 
 /* Remove regions that do not have landing pads.  This assumes
    that remove_unreachable_handlers has already been run, and
-   that we've just manipulated the landing pads since then.  */
+   that we've just manipulated the landing pads since then.
+
+   Preserve regions with landing pads and regions that prevent
+   exceptions from propagating further, even if these regions
+   are not reachable.  */
 
 static void
 remove_unreachable_handlers_no_lp (void)
 {
-  eh_region r;
-  int i;
+  eh_region region;
   sbitmap r_reachable;
-  basic_block bb;
+  unsigned i;
 
-  r_reachable = sbitmap_alloc (cfun->eh->region_array->length ());
-  bitmap_clear (r_reachable);
+  mark_reachable_handlers (&r_reachable, /*lp_reachablep=*/NULL);
 
-  FOR_EACH_BB (bb)
+  FOR_EACH_VEC_SAFE_ELT (cfun->eh->region_array, i, region)
     {
-      gimple stmt = last_stmt (bb);
-      if (stmt)
-	/* Avoid removing regions referenced from RESX/EH_DISPATCH.  */
-	switch (gimple_code (stmt))
-	  {
-	  case GIMPLE_RESX:
-	    bitmap_set_bit (r_reachable, gimple_resx_region (stmt));
-	    break;
-	  case GIMPLE_EH_DISPATCH:
-	    bitmap_set_bit (r_reachable, gimple_eh_dispatch_region (stmt));
-	    break;
-	  default:
-	    break;
-	  }
+      if (! region)
+	continue;
+
+      if (region->landing_pads != NULL
+	  || region->type == ERT_MUST_NOT_THROW)
+	bitmap_set_bit (r_reachable, region->index);
+
+      if (dump_file
+	  && !bitmap_bit_p (r_reachable, region->index))
+	fprintf (dump_file,
+		 "Removing unreachable region %d\n",
+		 region->index);
     }
 
-  for (i = 1; cfun->eh->region_array->iterate (i, &r); ++i)
-    if (r && r->landing_pads == NULL && r->type != ERT_MUST_NOT_THROW
-	&& !bitmap_bit_p (r_reachable, i))
-      {
-	if (dump_file)
-	  fprintf (dump_file, "Removing unreachable region %d\n", i);
-	remove_eh_handler (r);
-      }
+  remove_unreachable_eh_regions (r_reachable);
 
   sbitmap_free (r_reachable);
 }