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

[gcc.git] / gcc / tree-ssa-threadupdate.c

diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 24d0f42a168dca4c09a8f06d79931f9afb9fbff0..ad727a1afec5249da9fb18d9b15656d4685d73fb 100644 (file)
--- a/gcc/tree-ssa-threadupdate.c
+++ b/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