JumpPatchSites can/should easily deal with uint8 sized offsets.

src/x64/full-codegen-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 56 matching lines @@
   void EmitJumpIfSmi(Register reg,
                      Label* target,
                      Label::Distance near_jump = Label::kFar) {
     __ testb(reg, Immediate(kSmiTagMask));
     EmitJump(carry, target, near_jump);  // Never taken before patched.
   }
 
   void EmitPatchInfo() {
     if (patch_site_.is_bound()) {
       int delta_to_patch_site = masm_->SizeOfCodeGeneratedSince(&patch_site_);
-      ASSERT(is_int8(delta_to_patch_site));
+      ASSERT(is_uint8(delta_to_patch_site));
       __ testl(rax, Immediate(delta_to_patch_site));
 #ifdef DEBUG
       info_emitted_ = true;
 #endif
     } else {
       __ nop();  // Signals no inlined code.
     }
   }
 
  private:
@@ skipping 4829 matching lines @@
   ASSERT_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64