MIPS64: Add a check to addiu simulation according to the specification.

src/mips64/simulator-mips64.cc

 // Copyright 2011 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.
 
 #include <limits.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_MIPS64
@@ skipping 4395 matching lines @@
           if (rs_reg == 0) {  // BNEZALC
             BranchAndLinkCompactHelper(rt != 0, 16);
           } else {  // BNEC
             BranchCompactHelper(rt != rs, 16);
           }
         }
       }
       break;
     // ------------- Arithmetic instructions.
     case ADDIU: {
+      DCHECK(is_int32(rs));
       int32_t alu32_out = static_cast<int32_t>(rs + se_imm16);
       // Sign-extend result of 32bit operation into 64bit register.
       SetResult(rt_reg, static_cast<int64_t>(alu32_out));
       break;
     }
     case DADDIU:
       SetResult(rt_reg, rs + se_imm16);
       break;
     case SLTI:
       SetResult(rt_reg, rs < se_imm16 ? 1 : 0);
@@ skipping 511 matching lines @@
 }
 
 
 #undef UNSUPPORTED
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_MIPS64