Revert r40367.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index 56630ad0fb40d9dc6d445baa7c0907c7033d287a..cdefacb4d6c93adbf812fe25f268681d5de0eeb3 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -2387,37 +2387,17 @@ void EffectGraphVisitor::VisitStringInterpolateNode(
     StringInterpolateNode* node) {
   ValueGraphVisitor for_argument(owner());
   ArrayNode* arguments = node->value();
+  bool is_singleton = false;
   if (arguments->length() == 1) {
-    ZoneGrowableArray<PushArgumentInstr*>* values =
-        new(I) ZoneGrowableArray<PushArgumentInstr*>(1);
     arguments->ElementAt(0)->Visit(&for_argument);
-    Append(for_argument);
-    PushArgumentInstr* push_arg = PushArgument(for_argument.value());
-    values->Add(push_arg);
-    const int kNumberOfArguments = 1;
-    const Array& kNoArgumentNames = Object::null_array();
-    const Class& cls =
-        Class::Handle(Library::LookupCoreClass(Symbols::StringBase()));
-    ASSERT(!cls.IsNull());
-    const Function& function = Function::Handle(
-        Resolver::ResolveStatic(
-            cls,
-            Library::PrivateCoreLibName(Symbols::InterpolateSingle()),
-            kNumberOfArguments,
-            kNoArgumentNames));
-    StaticCallInstr* call =
-        new(I) StaticCallInstr(node->token_pos(),
-                               function,
-                               kNoArgumentNames,
-                               values,
-                               owner()->ic_data_array());
-    ReturnDefinition(call);
-    return;
+    is_singleton = true;
+  } else {
+    arguments->Visit(&for_argument);
   }
-  arguments->Visit(&for_argument);
   Append(for_argument);
   StringInterpolateInstr* instr =
-      new(I) StringInterpolateInstr(for_argument.value(), node->token_pos());
+      new(I) StringInterpolateInstr(for_argument.value(), node->token_pos(),
+                                    is_singleton);
   ReturnDefinition(instr);
 }