Fix overflow check in the Smi::ShiftOp.

runtime/vm/object.cc

 // Copyright (c) 2012, 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 "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 15885 matching lines @@
   intptr_t result = 0;
   const intptr_t left_value = Value();
   const intptr_t right_value = other.Value();
   ASSERT(right_value >= 0);
   switch (kind) {
     case Token::kSHL: {
       if ((left_value == 0) || (right_value == 0)) {
         return raw();
       }
       { // Check for overflow.
-        int cnt = Utils::HighestBit(left_value);
-        if ((cnt + right_value) >= Smi::kBits) {
-          if ((cnt + right_value) >= Mint::kBits) {
+        int cnt = Utils::BitLength(left_value);
+        if ((cnt + right_value) > Smi::kBits) {
+          if ((cnt + right_value) > Mint::kBits) {
             return Bigint::NewFromShiftedInt64(left_value, right_value);
           } else {
             int64_t left_64 = left_value;
             return Integer::New(left_64 << right_value, Heap::kNew, silent);
           }
         }
       }
       result = left_value << right_value;
       break;
     }
@@ skipping 4497 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart