[WIP] Initial CallFunctionCallback builtin.

src/assembler.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 1071 matching lines @@
   void* address_;
 };
 
 V8_EXPORT_PRIVATE bool operator==(ExternalReference, ExternalReference);
 bool operator!=(ExternalReference, ExternalReference);
 
 size_t hash_value(ExternalReference);
 
 V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream&, ExternalReference);
 
+inline int AddressOffset(ExternalReference ref0, ExternalReference ref1) {
+  ptrdiff_t offset = ref0.address() - ref1.address();
+  // Check that fits into int.
+  DCHECK_EQ(offset, static_cast<int>(offset));
+  return static_cast<int>(offset);
+}
+
 // -----------------------------------------------------------------------------
 // Utility functions
 
 inline int NumberOfBitsSet(uint32_t x) {
   unsigned int num_bits_set;
   for (num_bits_set = 0; x; x >>= 1) {
     num_bits_set += x & 1;
   }
   return num_bits_set;
 }
@@ skipping 154 matching lines @@
     std::vector<ConstantPoolEntry> shared_entries;
   };
 
   Label emitted_label_;  // Records pc_offset of emitted pool
   PerTypeEntryInfo info_[ConstantPoolEntry::NUMBER_OF_TYPES];
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_ASSEMBLER_H_