Use shorter write-barrier filtering sequence when value is known to be non-smi.

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 6105fc3538f7ee06f73c73edc74f7ab6154a9978..114edfda49c049ef7a0d6212c76fda641f766832 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -2837,6 +2837,13 @@ class StoreInstanceFieldInstr : public TemplateDefinition<2> {
   virtual bool HasSideEffect() const { return true; }
 
  private:
+  ValueSminess CanValueBeSmi() const {

[Ivan Posva, 2013/03/22 04:11:35]

Somehow I have an issue with the ValueSminess enum. Here your return a enum
result for something that clearly only has a boolean answer. "Can the value be
Smi?"

[Vyacheslav Egorov (Google), 2013/03/22 11:22:50]

Done.

+    const intptr_t cid = value()->Type()->ToNullableCid();
+    // Write barrier is skipped for nullable and non-nullable smis.
+    ASSERT(cid != kSmiCid);
+    return (cid == kDynamicCid) ? kValueCanBeSmi : kValueIsNotSmi;
+  }
+
   const Field& field_;
   const StoreBarrierType emit_store_barrier_;