DBC: Fix smi shl with large (>word-size) shift counts

runtime/vm/simulator_dbc.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_DBC)
 
@@ skipping 1965 matching lines @@
       *reinterpret_cast<intptr_t*>(&FP[rA]) =
           (res < 0) ? ((rhs < 0) ? (res - rhs) : (res + rhs)) : res;
       pc++;
     }
     DISPATCH();
   }
 
   {
     BYTECODE(Shl, A_B_C);
     const intptr_t rhs = reinterpret_cast<intptr_t>(FP[rC]) >> kSmiTagSize;
-    if (rhs >= 0) {
+    if (static_cast<uintptr_t>(rhs) < kBitsPerWord) {
       const intptr_t lhs = reinterpret_cast<intptr_t>(FP[rB]);
       const intptr_t res = lhs << rhs;
       if (lhs == (res >> rhs)) {
         *reinterpret_cast<intptr_t*>(&FP[rA]) = res;
         pc++;
       }
     }
     DISPATCH();
   }
 
@@ skipping 1757 matching lines @@
   pc_ = pc;
   special_[kExceptionSpecialIndex] = raw_exception;
   special_[kStacktraceSpecialIndex] = raw_stacktrace;
   buf->Longjmp();
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC