[clang] [clang] Optimize Lexer hot path to reduce compile time (PR #177153)

[Nikita Popov via cfe-commits]

nikic wrote:

It doesn't seem to make any difference: https://llvm-compile-time-tracker.com/compare.php?from=b9760dc6fbd65a29fb6773539f19b7c964da3e85&to=b577b0ceeb7e301c3e926f4d1976cf13af4bbcdc&stat=instructions:u

https://github.com/llvm/llvm-project/pull/177153