Tweaks for speed in integer arithmetic runtime.

runtime/lib/integers.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/bootstrap_natives.h"
 
 #include "include/dart_api.h"
 #include "vm/bigint_operations.h"
 #include "vm/dart_entry.h"
 #include "vm/dart_api_impl.h"
@@ skipping 264 matching lines @@
     Exceptions::ThrowArgumentError(amount);
   }
   if (value.IsSmi()) {
     const Smi& smi_value = Smi::Cast(value);
     return smi_value.ShiftOp(kind, amount, silent);
   }
   Bigint& big_value = Bigint::Handle();
   if (value.IsMint()) {
     const int64_t mint_value = value.AsInt64Value();
     const int count = Utils::HighestBit(mint_value);
-    if ((count + amount.Value()) < Mint::kBits) {
+    int shift_count = amount.Value();
+    if (kind == Token::kSHR) {
+      shift_count = -shift_count;
+    }

[srdjan, 2014/07/09 17:05:16]

s/int/intptr_t/

[regis, 2014/07/09 17:15:51]

Done.

+    if ((count + shift_count) < Mint::kBits) {
       switch (kind) {
         case Token::kSHL:
-          return Integer::New(mint_value << amount.Value(), Heap::kNew, silent);
+          return Integer::New(mint_value << shift_count, Heap::kNew, silent);
         case Token::kSHR:
-          return Integer::New(mint_value >> amount.Value(), Heap::kNew, silent);
+          return Integer::New(mint_value >> -shift_count, Heap::kNew, silent);
         default:
           UNIMPLEMENTED();
       }
     } else {
       // Overflow in shift, use Bigints
       big_value = BigintOperations::NewFromInt64(mint_value);
     }
   } else {
     ASSERT(value.IsBigint());
     big_value = Bigint::Cast(value).raw();
@@ skipping 140 matching lines @@
   // Use the preallocated out of memory exception to avoid calling
   // into dart code or allocating any code.
   const Instance& exception =
       Instance::Handle(isolate->object_store()->out_of_memory());
   Exceptions::Throw(isolate, exception);
   UNREACHABLE();
   return 0;
 }
 
 }  // namespace dart