Return VARYING in range_on_path_entry if nothing found.

The problem here is that the solver's code solving unknown SSAs on entry
to a path was returning UNDEFINED if there were no incoming edges to the
start of the path that were not the function entry block.  This caused a
cascade of pain down stream.

Tested on x86-64 Linux.

	PR tree-optimization/102511

gcc/ChangeLog:

	* gimple-range-path.cc (path_range_query::range_on_path_entry):
	Return VARYING when nothing found.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr102511.c: New test.
	* gcc.dg/tree-ssa/ssa-dom-thread-14.c: Adjust.

1 files changed, 10 insertions, 1 deletions

diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
index 71e04e4..9da67d2 100644
--- a/gcc/gimple-range-path.cc
+++ b/gcc/gimple-range-path.cc
@@ -136,14 +136,23 @@ path_range_query::range_on_path_entry (irange &r, tree name)
 {
   int_range_max tmp;
   basic_block entry = entry_bb ();
+  bool changed = false;
+
   r.set_undefined ();
   for (unsigned i = 0; i < EDGE_COUNT (entry->preds); ++i)
     {
       edge e = EDGE_PRED (entry, i);
       if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
 	  && m_ranger.range_on_edge (tmp, e, name))
-	r.union_ (tmp);
+	{
+	  r.union_ (tmp);
+	  changed = true;
+	}
     }
+
+  // Make sure we don't return UNDEFINED by mistake.
+  if (!changed)
+    r.set_varying (TREE_TYPE (name));
 }
 
 // Return the range of NAME at the end of the path being analyzed.