JumpPatchSites can/should easily deal with uint8 sized offsets.

src/x64/ic-x64.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 1285 matching lines @@
   // If the instruction following the call is not a test al, nothing
   // was inlined.
   if (*test_instruction_address != Assembler::kTestAlByte) {
     ASSERT(*test_instruction_address == Assembler::kNopByte);
     return;
   }
 
   Address delta_address = test_instruction_address + 1;
   // The delta to the start of the map check instruction and the
   // condition code uses at the patched jump.
-  int8_t delta = *reinterpret_cast<int8_t*>(delta_address);
+  uint8_t delta = *reinterpret_cast<uint8_t*>(delta_address);
   if (FLAG_trace_ic) {
     PrintF("[  patching ic at %p, test=%p, delta=%d\n",
            address, test_instruction_address, delta);
   }
 
   // Patch with a short conditional jump. Enabling means switching from a short
   // jump-if-carry/not-carry to jump-if-zero/not-zero, whereas disabling is the
   // reverse operation of that.
   Address jmp_address = test_instruction_address - delta;
   ASSERT((check == ENABLE_INLINED_SMI_CHECK)
          ? (*jmp_address == Assembler::kJncShortOpcode ||
             *jmp_address == Assembler::kJcShortOpcode)
          : (*jmp_address == Assembler::kJnzShortOpcode ||
             *jmp_address == Assembler::kJzShortOpcode));
   Condition cc = (check == ENABLE_INLINED_SMI_CHECK)
       ? (*jmp_address == Assembler::kJncShortOpcode ? not_zero : zero)
       : (*jmp_address == Assembler::kJnzShortOpcode ? not_carry : carry);
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64