Steps to reproduce:

1. Open attached project
2. Change graphics API to 'Metal' for Mac Standalone
3. Build 'Test' scene
4. Attach the built app to Xcode project and observe the CPU/GPU frametime (this can only be done in macOS Sierra update, previous OSX versions don't have this functionality)

Repeat these steps with 5.5.0 (trunk) and metal/hlslcc/runtime branch, notice the difference in CPU and GPU frame times.

My results:
trunk:
CPU: 28 - 30ms
GPU: 29 - 30ms
metal/hlslcc/runtime:
CPU: 33 - 35ms
GPU: 33 - 36ms