Allign Intel macro assemblers with changes to ARM macro assembler

src/x64/macro-assembler-x64.cc

 // Copyright 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 1224 matching lines @@
                                              Register result_end,
                                              Register scratch,
                                              AllocationFlags flags) {
   ExternalReference new_space_allocation_top =
       ExternalReference::new_space_allocation_top_address();
 
   // Just return if allocation top is already known.
   if ((flags & RESULT_CONTAINS_TOP) != 0) {
     // No use of scratch if allocation top is provided.
     ASSERT(scratch.is(no_reg));
+#ifdef DEBUG
+    // Assert that result actually contains top on entry.
+    movq(kScratchRegister, new_space_allocation_top);
+    cmpq(result, Operand(kScratchRegister, 0));
+    Check(equal, "Unexpected allocation top");
+#endif
     return;
   }
 
   // Move address of new object to result. Use scratch register if available.
   if (scratch.is(no_reg)) {
     movq(kScratchRegister, new_space_allocation_top);
     movq(result, Operand(kScratchRegister, 0));
   } else {
     ASSERT(!scratch.is(result_end));
     movq(scratch, new_space_allocation_top);
@@ skipping 122 matching lines @@
   movq(kScratchRegister, new_space_allocation_top);
 #ifdef DEBUG
   cmpq(object, Operand(kScratchRegister, 0));
   Check(below, "Undo allocation of non allocated memory");
 #endif
   movq(Operand(kScratchRegister, 0), object);
 }
 
 
 } }  // namespace v8::internal