[demangler][NFC] Small cleanups and sync
Some precursor work to adding module demangling.
* some mismatched comment and code in the demangler
* a const fn was not marked thusly
* we use std::islower. A direct range check is smaller code (no function call),
and we know we're in ASCII-land and later in that same function make the same
assumption about upper-case contiguity. Heck, maybe just drop the switch's
precondition and rely on the optimizer to do its thing?
* the directory is cloned in two places, which had gotten out of sync.
Differential Revision: https://reviews.llvm.org/D117800
1 file changed