We’re going to be updating the stable branch (swift-5.0-branch) of Clang/LLVM to align with the LLVM 7.0 release tomorrow, September 14 around noon Pacific time. We don’t expect this to cause much disruption, but it will require swift developers to rebuild Clang/LLVM once the update is complete. A clean build may or may not be necessary, but it is recommended.
To prepare for this update, we're going to go ahead and update the Clang, LLVM, and Compiler-rt swift-5.0-branch content now. We will temporarily disable the automerger bots so that the stable branch does not get updated until tomorrow at noon.