re PR middle-end/52996 (ice in verify_loop_structure, at cfgloop.c:1567)

2012-12-21  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/52996
	* cprop.c (bypass_block): When loops are to be preserved
	do not bypass loop headers.  Revert earlier kludge to remove
	loops when doing that.

From-SVN: r194666

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 53bbd712442f7d336bf7f0acde426214c78638c7..f0563db6ad025a5b37afa082a3dd53556f79d459 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2012-12-21  Richard Biener  <rguenther@suse.de>
+
+       PR rtl-optimization/52996
+       * cprop.c (bypass_block): When loops are to be preserved
+       do not bypass loop headers.  Revert earlier kludge to remove
+       loops when doing that.
+
 2012-12-21  Richard Biener  <rguenther@suse.de>
 
        PR bootstrap/54659

diff --git a/gcc/cprop.c b/gcc/cprop.c
index ec896a46062dd706a8e5fb013602d80f4fe4ec41..463f81ff73beb0972b51b290f8e02ac48ad91697 100644 (file)
--- a/gcc/cprop.c
+++ b/gcc/cprop.c
@@ -1496,7 +1496,7 @@ bypass_block (basic_block bb, rtx setcc, rtx jump)
   rtx insn, note;
   edge e, edest;
   int change;
-  int may_be_loop_header;
+  int may_be_loop_header = false;
   unsigned removed_p;
   unsigned i;
   edge_iterator ei;
@@ -1510,27 +1510,22 @@ bypass_block (basic_block bb, rtx setcc, rtx jump)
   if (note)
     find_used_regs (&XEXP (note, 0), NULL);
 
-  /* Determine whether there are more latch edges.  Threading through
-     a loop header with more than one latch is delicate, see e.g.
-     tree-ssa-threadupdate.c:thread_through_loop_header.  */
   if (current_loops)
     {
-      may_be_loop_header = bb == bb->loop_father->header;
-      if (may_be_loop_header
-         && bb->loop_father->latch == NULL)
+      /* If we are to preserve loop structure then do not bypass
+         a loop header.  This will either rotate the loop, create
+        multiple entry loops or even irreducible regions.  */
+      if (bb == bb->loop_father->header)
        return 0;
     }
   else
     {
-      unsigned n_back_edges = 0;
       FOR_EACH_EDGE (e, ei, bb->preds)
        if (e->flags & EDGE_DFS_BACK)
-         n_back_edges++;
-
-      may_be_loop_header = n_back_edges > 0;
-
-      if (n_back_edges > 1)
-        return 0;
+         {
+           may_be_loop_header = true;
+           break;
+         }
     }
 
   change = 0;
@@ -1619,17 +1614,6 @@ bypass_block (basic_block bb, rtx setcc, rtx jump)
              && dest != old_dest
              && dest != EXIT_BLOCK_PTR)
             {
-             if (current_loops != NULL
-                 && e->src->loop_father->latch == e->src)
-               {
-                 /* ???  Now we are creating (or may create) a loop
-                    with multiple entries.  Simply mark it for
-                    removal.  Alternatively we could not do this
-                    threading.  */
-                 e->src->loop_father->header = NULL;
-                 e->src->loop_father->latch = NULL;
-               }
-
              redirect_edge_and_branch_force (e, dest);
 
              /* Copy the register setter to the redirected edge.