llvm-project

20f56d14 - [libc++abi] Fix C++ demangling for _BitInt type (#143466)

[libc++abi] Fix C++ demangling for _BitInt type (#143466) The front-end expects _BitInt to be available for substitution; ensure DB<n> is added to Subs in ItaniumDemangle.h. Also add a test case to libc++abi and sync the files to llvm/include/llvm.