re PR tree-optimization/59322 (ICE with segfault on valid code at -O1, -O2, and…

re PR tree-optimization/59322 (ICE with segfault on valid code at -O1, -O2, and -O3 on x86_64-linux-gnu)

	PR tree-optimization/59322
	* tree-ssa-threadedge.c (create_edge_and_update_destination_phis):
	Remove code which copied jump threading paths.

	PR tree-optimization/59322
	* gcc.c-torture/compile/pr59322.c: New test

From-SVN: r205617

gcc/ChangeLog

+2013-12-02  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/59322
+	* tree-ssa-threadedge.c (create_edge_and_update_destination_phis):
+	Remove code which copied jump threading paths.
+
 2013-12-02  Sriraman Tallam  <tmsriram@google.com>
 
 	PR target/58944

gcc/testsuite/ChangeLog

+2013-12-02  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/59322
+	* gcc.c-torture/compile/pr59322.c: New test
+
 2013-12-02  Sriraman Tallam  <tmsriram@google.com>
 
 	PR target/58944

gcc/testsuite/gcc.c-torture/compile/pr59322.c

+
+int a, b, d;
+short c;
+
+int
+foo ()
+{
+  for (b = 0; b; b = a)
+    for (c = 18; c < 10; c++)
+      {
+	d = c;
+	if (d)
+	  return 0;
+      }
+  return 0;
+}

gcc/tree-ssa-threadupdate.c

@@ -421,27 +421,22 @@ create_edge_and_update_destination_phis (struct redirection_data *rd,
   e->probability = REG_BR_PROB_BASE;
   e->count = bb->count;
 
-  /* We have to copy path -- which means creating a new vector as well
-     as all the jump_thread_edge entries.  */
-  if (rd->path->last ()->e->aux)
-    {
-      vec<jump_thread_edge *> *path = THREAD_PATH (rd->path->last ()->e);
-      vec<jump_thread_edge *> *copy = new vec<jump_thread_edge *> ();
+  /* We used to copy the thread path here.  That was added in 2007
+     and dutifully updated through the representation changes in 2013.
 
-      /* Sadly, the elements of the vector are pointers and need to
-	 be copied as well.  */
-      for (unsigned int i = 0; i < path->length (); i++)
-	{
-	  jump_thread_edge *x
-	    = new jump_thread_edge ((*path)[i]->e, (*path)[i]->type);
-	  copy->safe_push (x);
-	}
-      e->aux = (void *)copy;
-    }
-  else
-    {
-      e->aux = NULL;
-    }
+     In 2013 we added code to thread from an interior node through
+     the backedge to another interior node.  That runs after the code
+     to thread through loop headers from outside the loop.
+
+     The latter may delete edges in the CFG, including those
+     which appeared in the jump threading path we copied here.  Thus
+     we'd end up using a dangling pointer.
+
+     After reviewing the 2007/2011 code, I can't see how anything
+     depended on copying the AUX field and clearly copying the jump
+     threading path is problematical due to embedded edge pointers.
+     It has been removed.  */
+  e->aux = NULL;
 
   /* If there are any PHI nodes at the destination of the outgoing edge
      from the duplicate block, then we will need to add a new argument