Implement a simple register allocator that tries to keep instruction results in registers.

runtime/vm/growable_array.h

Index: runtime/vm/growable_array.h
diff --git a/runtime/vm/growable_array.h b/runtime/vm/growable_array.h
index 1223d719beba81943435a378115aea3784e8e6f1..49ae5fa230a731d39c1bc72b0a4d9e1d670982ec 100644
--- a/runtime/vm/growable_array.h
+++ b/runtime/vm/growable_array.h
@@ -68,6 +68,14 @@ class BaseGrowableArray : public B {
     length_ = 0;
   }
 
+  void RemoveFirst() {
+    ASSERT(length_ > 0);
+    length_--;
+    for (int i = 0; i < length_; i++) {
+      data_[i] = data_[i + 1];
+    }
+  }
+
   // Sort the array in place.
   inline void Sort(int compare(const T*, const T*));