Thomas Munro <thomas.munro@gmail.com> writes:
> Back in commit 4f658dc8 we gained src/port/fls.c. As anticipated by
> its commit message, we later finished up with something better in
> src/include/port/pg_bitutils.h. fls() ("find last set") is an
> off-by-one cousin of pg_leftmost_one_pos32(). I don't know why ffs()
> ("find first set", the rightmost variant) made it into POSIX while
> fls() did not, other than perhaps its more amusing name. fls() is
> present on *BSD, Macs and maybe more, but not everywhere, hence the
> configure test. Let's just do it with pg_bitutils.h instead, and drop
> some cruft? Open to better ideas on whether we need a new function,
I think we could probably just drop fls() entirely. It doesn't look
to me like any of the existing callers expect a zero argument, so they
could be converted to use pg_leftmost_one_pos32() pretty trivially.
I don't see that fls() is buying us anything that is worth requiring
readers to know yet another nonstandard function.
regards, tom lane