analyzer: show BB index in BEFORE_SUPERNODE's in-edge

This is useful for debugging how the analyzer handles phi nodes.

gcc/analyzer/ChangeLog:
	* program-point.cc (function_point::print): Show src BB index at
	BEFORE_SUPERNODE.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>
diff --git a/gcc/analyzer/program-point.cc b/gcc/analyzer/program-point.cc
index d8cfc61..d73b621 100644
--- a/gcc/analyzer/program-point.cc
+++ b/gcc/analyzer/program-point.cc
@@ -119,8 +119,15 @@
     case PK_BEFORE_SUPERNODE:
       {
 	if (m_from_edge)
-	  pp_printf (pp, "before SN: %i (from SN: %i)",
-		     m_supernode->m_index, m_from_edge->m_src->m_index);
+	  {
+	    if (basic_block bb = m_from_edge->m_src->m_bb)
+	      pp_printf (pp, "before SN: %i (from SN: %i (bb: %i))",
+			 m_supernode->m_index, m_from_edge->m_src->m_index,
+			 bb->index);
+	    else
+	      pp_printf (pp, "before SN: %i (from SN: %i)",
+			 m_supernode->m_index, m_from_edge->m_src->m_index);
+	  }
 	else
 	  pp_printf (pp, "before SN: %i (NULL from-edge)",
 		     m_supernode->m_index);