Fix signed / unsigned warnings for ?: operators reported by Xcode 4.x clang compiler.

src/hydrogen-instructions.cc

 // Copyright 2012 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 1330 matching lines @@
   left()->PrintNameTo(stream);
   stream->Add(" ");
   right()->PrintNameTo(stream);
   if (CheckFlag(kCanOverflow)) stream->Add(" !");
   if (CheckFlag(kBailoutOnMinusZero)) stream->Add(" -0?");
 }
 
 
 Range* HBitwise::InferRange(Zone* zone) {
   if (op() == Token::BIT_XOR) return HValue::InferRange(zone);
+  const int32_t kDefaultMask = static_cast<int32_t>(0xffffffff);
   int32_t left_mask = (left()->range() != NULL)
       ? left()->range()->Mask()
-      : 0xffffffff;
+      : kDefaultMask;
   int32_t right_mask = (right()->range() != NULL)
       ? right()->range()->Mask()
-      : 0xffffffff;
+      : kDefaultMask;
   int32_t result_mask = (op() == Token::BIT_AND)
       ? left_mask & right_mask
       : left_mask | right_mask;
   return (result_mask >= 0)
       ? new(zone) Range(0, result_mask)
       : HValue::InferRange(zone);
 }
 
 
 Range* HSar::InferRange(Zone* zone) {
@@ skipping 920 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal