X64: Convert smis to holding 32 bits of payload.

src/v8.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 160 matching lines @@
 
 bool V8::IdleNotification() {
   // Returning true tells the caller that there is no need to call
   // IdleNotification again.
   if (!FLAG_use_idle_notification) return true;
 
   // Tell the heap that it may want to adjust.
   return Heap::IdleNotification();
 }
 
+static const uint32_t kRandomPositiveSmiMax = 0x3fffffff;
 
 Smi* V8::RandomPositiveSmi() {
   uint32_t random = Random();
-  ASSERT(IsPowerOf2(Smi::kMaxValue + 1));
-  return Smi::FromInt(random & Smi::kMaxValue);
+  ASSERT(static_cast<uint32_t>(Smi::kMaxValue) >= kRandomPositiveSmiMax);
+  // kRandomPositiveSmiMax must match the value being divided
+  // by in math.js.
+  return Smi::FromInt(random & kRandomPositiveSmiMax);
 }
 
 } }  // namespace v8::internal