Implement shift left on ARM and re-enable previously disabled test.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2013, 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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 2166 matching lines @@
     // TODO(srdjan): Implement code below for is_truncating().
     // If left is constant, we know the maximal allowed size for right.
     const Object& obj = shift_left->left()->BoundConstant();
     if (obj.IsSmi()) {
       const intptr_t left_int = Smi::Cast(obj).Value();
       if (left_int == 0) {
         __ cmpq(right, Immediate(0));
         __ j(NEGATIVE, deopt);
         return;
       }
-      intptr_t tmp = (left_int > 0) ? left_int : ~left_int;
-      intptr_t max_right = kSmiBits;
-      while ((tmp >>= 1) != 0) {
-        max_right--;
-      }
+      const intptr_t max_right = kSmiBits - Utils::HighestBit(left_int);
       const bool right_needs_check =
           (right_range == NULL) ||
           !right_range->IsWithin(0, max_right - 1);
       if (right_needs_check) {
         __ cmpq(right,
           Immediate(reinterpret_cast<int64_t>(Smi::New(max_right))));
         __ j(ABOVE_EQUAL, deopt);
       }
       __ SmiUntag(right);
       __ shlq(left, right);
@@ skipping 2190 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64