As announced here: http://lists.llvm.org/pipermail/llvm-dev/2019-April/131786.html Grouped option syntax (POSIX Utility Conventions) does not play well with -long-option A subsequent change will reject -long-option.
Assembler now permits pairs like 'v0:1', which are encoded differently from the odd-first pairs like 'v1:0'. The compiler will require more work to leverage these new register pairs.