title: How to speedup iOS Xcode compilation
body: <p>I have two projects based on LLVM Objective-C/C with 1M lines of code and 1.5M lines of code. </p>
  
  <p>The 1.5M LoC project compiles faster for some unclear reason. It doesn't use precompiled headers and there is no explanation I could find. </p>
  
  <p>I've added precompiled headers and included the biggest offenders, I've disabled dSYM generation, made the code compile ARM 7 only (not 7s) reduced the amount of optimizations to O3. Still the builds are much slower, the projects are pretty similar in structure but I can't see any major difference that would justify the slower build.</p>
  
  <p>The faster building project was constructed with an older version of xcode but both are compiled with xcode 5.</p>