[interpreter] Bytecode register optimizer.

test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden

Index: test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden
diff --git a/test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden b/test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden
index a8338e74d4cc78bf72bf69c4fbc2cd325535892f..a132a925f9ccf6b9a19c92ac16d2542ce1aec066 100644
--- a/test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden
+++ b/test/cctest/interpreter/bytecode_expectations/ArrayLiterals.golden
@@ -29,9 +29,9 @@ handlers: [
 snippet: "
   var a = 1; return [ a, a + 1 ];
 "
-frame size: 4
+frame size: 3
 parameter count: 1
-bytecode array length: 39
+bytecode array length: 35
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaSmi), U8(1),
@@ -44,10 +44,8 @@ bytecodes: [
                 B(StaKeyedPropertySloppy), R(2), R(1), U8(1),
                 B(LdaSmi), U8(1),
                 B(Star), R(1),
-  /*   57 E> */ B(Ldar), R(0),
-                B(Star), R(3),
-                B(LdaSmi), U8(1),
-                B(Add), R(3),
+  /*   57 E> */ B(LdaSmi), U8(1),
+                B(Add), R(0),
                 B(StaKeyedPropertySloppy), R(2), R(1), U8(1),
                 B(Ldar), R(2),
   /*   66 S> */ B(Return),
@@ -80,9 +78,9 @@ handlers: [
 snippet: "
   var a = 1; return [ [ a, 2 ], [ a + 2 ] ];
 "
-frame size: 6
+frame size: 5
 parameter count: 1
-bytecode array length: 69
+bytecode array length: 65
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaSmi), U8(1),
@@ -105,10 +103,8 @@ bytecodes: [
                 B(Star), R(4),
                 B(LdaZero),
                 B(Star), R(3),
-  /*   66 E> */ B(Ldar), R(0),
-                B(Star), R(5),
-                B(LdaSmi), U8(2),
-                B(Add), R(5),
+  /*   66 E> */ B(LdaSmi), U8(2),
+                B(Add), R(0),
                 B(StaKeyedPropertySloppy), R(4), R(3), U8(3),
                 B(Ldar), R(4),
                 B(StaKeyedPropertySloppy), R(2), R(1), U8(5),