Xcode 8.3 produces binaries 3x larger than Xcode 8.2.1
This appears to be bitcode.
It probably means they just starting making use of more metadata or something that is now included in the bitcode.Bitcode also now deliberately trades off size vs speed and includes indexes used for LTO, etc.
They could be including those.You should almost always expect bitcode to get beat by "llvm-dis|xz", because the goal of bitcode is not to be the most compact possible format, but instead, a compact format the compiler can use effectively :)Now, if actual on-device binary sizes increased, my guesses would be:1. it now includes bitcode, or another architecture, in the binary (which would be interesting)2. Something has gone horribly horribly wrong :P  Really, speaking as a guy whose org maintains the toolchains for platforms like this, there's a 0% chance we wouldn't notice a 2x-3x size increase.