[Interpreter] Register conversion fix and test.

src/interpreter/bytecode-array-builder.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 #define V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 
 #include <vector>
 
 #include "src/ast.h"
@@ skipping 66 matching lines @@
 class Register {
  public:
   static const int kMaxRegisterIndex = 128;
 
   explicit Register(int index) : index_(index) {
     DCHECK_LE(index_, kMaxRegisterIndex);
   }
 
   int index() { return index_; }
   uint8_t ToOperand() { return static_cast<uint8_t>(-index_); }
-  static Register FromOperand(uint8_t operand) { return Register(-operand); }
+  static Register FromOperand(uint8_t operand) {
+    return Register(-static_cast<int8_t>(operand));
+  }
 
  private:
   void* operator new(size_t size);
   void operator delete(void* p);
 
   int index_;
 };
 
 // A stack-allocated class than allows the instantiator to allocate
 // temporary registers that are cleaned up when scope is closed.
@@ skipping 13 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(TemporaryRegisterScope);
 };
 
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_