X64: Implement unary subtraction, ObjectPair. 350 tests still fail.

src/runtime.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 4474 matching lines @@
 }
 
 
 // A mechanism to return pairs of Object*'s. This is somewhat
 // compiler-dependent as it assumes that a 64-bit value (a long long)
 // is returned via two registers (edx:eax on ia32). Both the ia32 and
 // arm platform support this; it is mostly an issue of "coaxing" the
 // compiler to do the right thing.
 //
 // TODO(1236026): This is a non-portable hack that should be removed.
-// TODO(x64): Definitely!
+#ifdef V8_HOST_ARCH_64_BIT
+// Tested with GCC, not with MSVC.
+struct ObjectPair {
+  Object* x;
+  Object* y;
+};
+static inline ObjectPair MakePair(Object* x, Object* y) {
+  ObjectPair result = {x, y};
+  return result;  // Pointers x and y returned in rax and rdx, in AMD-x64-abi.
+}
+#else
 typedef uint64_t ObjectPair;
 static inline ObjectPair MakePair(Object* x, Object* y) {
-#if V8_HOST_ARCH_64_BIT
-  UNIMPLEMENTED();
-  return 0;
-#else
   return reinterpret_cast<uint32_t>(x) |
       (reinterpret_cast<ObjectPair>(y) << 32);
+}
 #endif
-}
+
+
 
 
 static inline Object* Unhole(Object* x, PropertyAttributes attributes) {
   ASSERT(!x->IsTheHole() || (attributes & READ_ONLY) != 0);
   USE(attributes);
   return x->IsTheHole() ? Heap::undefined_value() : x;
 }
 
 
 static JSObject* ComputeReceiverForNonGlobal(JSObject* holder) {
@@ skipping 3012 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage();
   }
 }
 
 
 } }  // namespace v8::internal