[interpreter] Bytecode register optimizer.

test/cctest/interpreter/bytecode_expectations/GlobalCompoundExpressions.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: string
 execute: yes
 wrap: no
 test function name: f
 
 ---
 snippet: "
   var global = 1;
   function f() { return global &= 1; }
   f();
 "
 frame size: 1
 parameter count: 1
-bytecode array length: 13
+bytecode array length: 14
 bytecodes: [
   /*   26 E> */ B(StackCheck),
-  /*   31 S> */ B(LdrGlobal), U8(0), U8(1), R(0),
+  /*   31 S> */ B(LdaGlobal), U8(0), U8(1),
+                B(Star), R(0),
                 B(LdaSmi), U8(1),
                 B(BitwiseAnd), R(0),
   /*   45 E> */ B(StaGlobalSloppy), U8(0), U8(3),
   /*   51 S> */ B(Return),
 ]
 constant pool: [
   "global",
 ]
 handlers: [
 ]
 
 ---
 snippet: "
   unallocated = 1;
   function f() { return unallocated += 1; }
   f();
 "
 frame size: 1
 parameter count: 1
-bytecode array length: 13
+bytecode array length: 14
 bytecodes: [
   /*   27 E> */ B(StackCheck),
-  /*   32 S> */ B(LdrGlobal), U8(0), U8(1), R(0),
+  /*   32 S> */ B(LdaGlobal), U8(0), U8(1),
+                B(Star), R(0),
                 B(LdaSmi), U8(1),
                 B(Add), R(0),
   /*   51 E> */ B(StaGlobalSloppy), U8(0), U8(3),
   /*   57 S> */ B(Return),
 ]
 constant pool: [
   "unallocated",
 ]
 handlers: [
 ]