[interpreter] Bytecode register optimizer.

test/cctest/interpreter/bytecode_expectations/NewTarget.golden

Index: test/cctest/interpreter/bytecode_expectations/NewTarget.golden
diff --git a/test/cctest/interpreter/bytecode_expectations/NewTarget.golden b/test/cctest/interpreter/bytecode_expectations/NewTarget.golden
index 08d2a13d640070e69689e7083c1621e584e9ad71..398b857c1f782474f5387e4963d4d23d069adca7 100644
--- a/test/cctest/interpreter/bytecode_expectations/NewTarget.golden
+++ b/test/cctest/interpreter/bytecode_expectations/NewTarget.golden
@@ -13,12 +13,11 @@ snippet: "
 "
 frame size: 2
 parameter count: 1
-bytecode array length: 19
+bytecode array length: 18
 bytecodes: [
-                B(Ldar), R(new_target),
-                B(Star), R(0),
+                B(Mov), R(new_target), R(0),
   /*   30 E> */ B(StackCheck),
-  /*   34 S> */ B(Ldar), R(0),
+  /*   34 S> */ B(Ldar), R(new_target),
                 B(JumpIfNotHole), U8(11),
                 B(LdaConstant), U8(0),
                 B(Star), R(1),
@@ -37,12 +36,11 @@ snippet: "
 "
 frame size: 2
 parameter count: 1
-bytecode array length: 20
+bytecode array length: 19
 bytecodes: [
-                B(Ldar), R(new_target),
-                B(Star), R(0),
+                B(Mov), R(new_target), R(0),
   /*   30 E> */ B(StackCheck),
-  /*   34 S> */ B(Ldar), R(0),
+  /*   34 S> */ B(Ldar), R(new_target),
                 B(JumpIfNotHole), U8(11),
                 B(LdaConstant), U8(0),
                 B(Star), R(1),