[interpreter] Bytecode register optimizer.

test/cctest/interpreter/bytecode_expectations/DoExpression.golden

Index: test/cctest/interpreter/bytecode_expectations/DoExpression.golden
diff --git a/test/cctest/interpreter/bytecode_expectations/DoExpression.golden b/test/cctest/interpreter/bytecode_expectations/DoExpression.golden
index 53f5d3dffefe81641318e84b6dd13399ef2e725d..49221ea44a561e93ff42758abe9bf6576a583bbe 100644
--- a/test/cctest/interpreter/bytecode_expectations/DoExpression.golden
+++ b/test/cctest/interpreter/bytecode_expectations/DoExpression.golden
@@ -14,12 +14,12 @@ snippet: "
 "
 frame size: 2
 parameter count: 1
-bytecode array length: 7
+bytecode array length: 8
 bytecodes: [
   /*   30 E> */ B(StackCheck),
-  /*   42 S> */ B(Ldar), R(0),
-                B(Star), R(1),
-  /*   50 S> */ B(Nop),
+  /*   42 S> */ B(Nop),
+                B(Mov), R(0), R(1),
+  /*   50 S> */ B(Ldar), R(1),
   /*   60 S> */ B(Return),
 ]
 constant pool: [
@@ -66,8 +66,8 @@ bytecodes: [
   /*   71 E> */ B(Star), R(1),
                 B(Star), R(0),
   /*   74 S> */ B(Jump), U8(12),
-  /*   64 E> */ B(Ldar), R(0),
-                B(Star), R(1),
+  /*   64 E> */ B(Nop),
+                B(Mov), R(0), R(1),
   /*   84 S> */ B(LdaSmi), U8(20),
   /*   86 E> */ B(Star), R(1),
                 B(Jump), U8(-20),