Labels beginning with L (upper case only) are called local
labels. See Symbol Names. Normally you do not see such labels when
debugging, because they are intended for the use of programs (like
compilers) that compose assembler programs, not for your notice.
Normally both as and ld discard such labels, so you do not
normally debug with them.
This option tells as to retain those L... symbols
in the object file. Usually if you do this you also tell the linker
ld to preserve symbols whose names begin with L.
By default, a local label is any label beginning with L, but each target is allowed to redefine the local label prefix. On the HPPA local labels begin with L$.