diff mbox

PRE TLC, improve fake exit edge placement

Message ID alpine.LSU.2.20.1708011206490.10808@zhemvz.fhfr.qr
State New
Headers show

Commit Message

Richard Biener Aug. 1, 2017, 10:09 a.m. UTC 
When working on PR81181 I ran into some things I wanted to clean up
several times.  First a few PRE cleanups done for the fix.  Second,
the fake exit edges we add for infinite loops happen to start from
loop headers rather than latches which is somewhat confusing and
making PRE dataflow order more confusing than it already is.  The
patch makes it originate from the source of the closing edge instead
of from the destination.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2017-08-01  Richard Biener  <rguenther@suse.de>

	* tree-ssa-pre.c (print_pre_expr): Handle NULL expr.
	(compute_antic): Seed worklist with exit block predecessors.
	* cfganal.c (dfs_find_deadend): For a cycle return the source
	of the edge closing it.
diff mbox

Patch

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c	(revision 250725)
+++ gcc/tree-ssa-pre.c	(working copy)
@@ -837,7 +840,7 @@  bitmap_set_and (bitmap_set_t dest, bitma
     }
 }
 
-/* Subtract all values and expressions contained in ORIG from DEST.  */
+/* Subtract all expressions contained in ORIG from DEST.  */
 
 static bitmap_set_t
 bitmap_set_subtract (bitmap_set_t dest, bitmap_set_t orig)
@@ -859,7 +862,7 @@  bitmap_set_subtract (bitmap_set_t dest,
   return result;
 }
 
-/* Subtract all the values in bitmap set B from bitmap set A.  */
+/* Subtract all values in bitmap set B from bitmap set A.  */
 
 static void
 bitmap_set_subtract_values (bitmap_set_t a, bitmap_set_t b)
@@ -987,6 +990,11 @@  bitmap_value_insert_into_set (bitmap_set
 static void
 print_pre_expr (FILE *outfile, const pre_expr expr)
 {
+  if (! expr)
+    {
+      fprintf (outfile, "NULL");
+      return;
+    }
   switch (expr->kind)
     {
     case CONSTANT:
@@ -2418,7 +2473,9 @@  compute_antic (void)
   inverted_post_order_compute (&postorder);
 
   auto_sbitmap worklist (last_basic_block_for_fn (cfun) + 1);
-  bitmap_ones (worklist);
+  bitmap_clear (worklist);
+  FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
+    bitmap_set_bit (worklist, e->src->index);
   while (changed)
     {
       if (dump_file && (dump_flags & TDF_DETAILS))
Index: gcc/cfganal.c
===================================================================
--- gcc/cfganal.c	(revision 250725)
+++ gcc/cfganal.c	(working copy)
@@ -737,23 +737,24 @@  post_order_compute (int *post_order, boo
 basic_block
 dfs_find_deadend (basic_block bb)
 {
-  bitmap visited = BITMAP_ALLOC (NULL);
+  auto_bitmap visited;
+  basic_block next = bb;
 
   for (;;)
     {
-      if (EDGE_COUNT (bb->succs) == 0
-	  || ! bitmap_set_bit (visited, bb->index))
-        {
-          BITMAP_FREE (visited);
-          return bb;
-        }
+      if (EDGE_COUNT (next->succs) == 0)
+	return next;
 
+      if (! bitmap_set_bit (visited, next->index))
+	return bb;
+
+      bb = next;
       /* If we are in an analyzed cycle make sure to try exiting it.
          Note this is a heuristic only and expected to work when loop
 	 fixup is needed as well.  */
       if (! bb->loop_father
 	  || ! loop_outer (bb->loop_father))
-	bb = EDGE_SUCC (bb, 0)->dest;
+	next = EDGE_SUCC (bb, 0)->dest;
       else
 	{
 	  edge_iterator ei;
@@ -761,7 +762,7 @@  dfs_find_deadend (basic_block bb)
 	  FOR_EACH_EDGE (e, ei, bb->succs)
 	    if (loop_exit_edge_p (bb->loop_father, e))
 	      break;
-	  bb = e ? e->dest : EDGE_SUCC (bb, 0)->dest;
+	  next = e ? e->dest : EDGE_SUCC (bb, 0)->dest;
 	}
     }