Call special VM interpolate for single element interpolation.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 32f546399ce0ea7ac51c89990ee7bbfdc697486a..37481f138d231751ad92b1b5bd78ac40153e6d4d 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -3800,11 +3800,15 @@ class StringToCharCodeInstr : public TemplateDefinition<1> {
 
 class StringInterpolateInstr : public TemplateDefinition<1> {
  public:
-  StringInterpolateInstr(Value* value, intptr_t token_pos)
-      : token_pos_(token_pos), function_(Function::Handle()) {
+  StringInterpolateInstr(Value* value, intptr_t token_pos, bool singleton)
+      : token_pos_(token_pos),
+        function_(Function::Handle()),
+        singleton_(singleton) {
     SetInputAt(0, value);
   }
 
+  bool IsSingleton() const { return singleton_; }

[Florian Schneider, 2014/09/12 10:33:37]

This accessor may be removed if not needed.

[Lasse Reichstein Nielsen, 2014/09/12 12:49:39]

Done.

+
   Value* value() const { return inputs_[0]; }
   virtual intptr_t token_pos() const { return token_pos_; }
 
@@ -3823,6 +3827,7 @@ class StringInterpolateInstr : public TemplateDefinition<1> {
  private:
   const intptr_t token_pos_;
   Function& function_;
+  const bool singleton_;

[Florian Schneider, 2014/09/12 10:33:37]

I'd rename singleton_ to is_singleton_ for consistency with other bool members.

[Lasse Reichstein Nielsen, 2014/09/12 12:49:39]

Done.

 
   DISALLOW_COPY_AND_ASSIGN(StringInterpolateInstr);
 };