diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index cb343956947..9054178018e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2019-11-13  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* tree-vectorizer.h (vect_nop_conversion_p): Declare.
+	* tree-vect-stmts.c (vect_nop_conversion_p): New function.
+	(vectorizable_assignment): Don't add a cost for nop conversions.
+	* tree-vect-loop.c (vect_compute_single_scalar_iteration_cost):
+	Likewise.
+	* tree-vect-slp.c (vect_bb_slp_scalar_cost): Likewise.
+
 2019-11-13  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* tree-vect-stmts.c (vect_model_promotion_demotion_cost): Take the
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index d9f413430dc..75ec9e67a5c 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -1125,7 +1125,9 @@ vect_compute_single_scalar_iteration_cost (loop_vec_info loop_vinfo)
              else
                kind = scalar_store;
             }
-          else
+	  else if (vect_nop_conversion_p (stmt_info))
+	    continue;
+	  else
             kind = scalar_stmt;
 
 	  record_stmt_cost (&LOOP_VINFO_SCALAR_ITERATION_COST (loop_vinfo),
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 4bc0cc77de4..a2c70ec5cd6 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2893,6 +2893,8 @@ vect_bb_slp_scalar_cost (basic_block bb,
           else
 	    kind = scalar_store;
         }
+      else if (vect_nop_conversion_p (stmt_info))
+	continue;
       else
 	kind = scalar_stmt;
       record_stmt_cost (cost_vec, 1, kind, stmt_info, 0, vect_body);
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 53f4189d939..c8a43ada16f 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -5281,6 +5281,29 @@ vectorizable_conversion (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
   return true;
 }
 
+/* Return true if we can assume from the scalar form of STMT_INFO that
+   neither the scalar nor the vector forms will generate code.  STMT_INFO
+   is known not to involve a data reference.  */
+
+bool
+vect_nop_conversion_p (stmt_vec_info stmt_info)
+{
+  gassign *stmt = dyn_cast <gassign *> (stmt_info->stmt);
+  if (!stmt)
+    return false;
+
+  tree lhs = gimple_assign_lhs (stmt);
+  tree_code code = gimple_assign_rhs_code (stmt);
+  tree rhs = gimple_assign_rhs1 (stmt);
+
+  if (code == SSA_NAME || code == VIEW_CONVERT_EXPR)
+    return true;
+
+  if (CONVERT_EXPR_CODE_P (code))
+    return tree_nop_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs));
+
+  return false;
+}
 
 /* Function vectorizable_assignment.
 
@@ -5396,7 +5419,9 @@ vectorizable_assignment (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
     {
       STMT_VINFO_TYPE (stmt_info) = assignment_vec_info_type;
       DUMP_VECT_SCOPE ("vectorizable_assignment");
-      vect_model_simple_cost (stmt_info, ncopies, dt, ndts, slp_node, cost_vec);
+      if (!vect_nop_conversion_p (stmt_info))
+	vect_model_simple_cost (stmt_info, ncopies, dt, ndts, slp_node,
+				cost_vec);
       return true;
     }
 
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index e556e0e9888..e93ccc74c66 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -1650,6 +1650,7 @@ extern tree vect_get_vec_def_for_stmt_copy (vec_info *, tree);
 extern bool vect_transform_stmt (stmt_vec_info, gimple_stmt_iterator *,
 				 slp_tree, slp_instance);
 extern void vect_remove_stores (stmt_vec_info);
+extern bool vect_nop_conversion_p (stmt_vec_info);
 extern opt_result vect_analyze_stmt (stmt_vec_info, bool *, slp_tree,
 				     slp_instance, stmt_vector_for_cost *);
 extern void vect_get_load_cost (stmt_vec_info, int, bool,