title: clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
body: <p>I don't know what causes it.</p>
  
  <p>It does not happen at iPhone 5 and simulators. It have been happened only my original device iPhone 7.</p>
  
  <pre><code>fatal error: error in backend: Error while trying to spill X0 from class GPR64: Cannot scavenge register without an emergency spill slot!
  clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
  Apple LLVM version 9.0.0 (clang-900.0.34.1)
  Target: aarch64-apple-darwin16.7.0
  Thread model: posix
  InstalledDir: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
  clang: note: diagnostic msg: PLEASE submit a bug report to http://developer.apple.com/bugreporter/ and include the crash backtrace, preprocessed source, and associated run script.
  clang: note: diagnostic msg: 
  ********************
  
  PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
  Preprocessed source(s) and associated run script(s) are located at:
  clang: note: diagnostic msg: /var/folders/xg/tgwkzqt15xd9jprnv9f0gn4c0000gn/T/CityArray-6e6c1e.m
  clang: note: diagnostic msg: /var/folders/xg/tgwkzqt15xd9jprnv9f0gn4c0000gn/T/CityArray-6e6c1e.cache
  clang: note: diagnostic msg: /var/folders/xg/tgwkzqt15xd9jprnv9f0gn4c0000gn/T/CityArray-6e6c1e.sh
  clang: note: diagnostic msg: Crash backtrace is located in
  clang: note: diagnostic msg: /Users/junhyun/Library/Logs/DiagnosticReports/clang_&lt;YYYY-MM-DD-HHMMSS&gt;_&lt;hostname&gt;.crash
  clang: note: diagnostic msg: (choose the .crash file that corresponds to your crash)
  clang: note: diagnostic msg: 
  
  ********************
  </code></pre>