Re: [PATCH v4] Avoid manual shift-and-test logic in AllocSetFreeIndex

Jeremy Kerr <jk@ozlabs.org> writes:
> Rather than testing single bits in a loop, change AllocSetFreeIndex to
> use the __builtin_clz() function to calculate the chunk index.

Per subsequent discussion and testing, I've committed a patch that
uses a lookup table instead of depending on __builtin_clz().
http://archives.postgresql.org/message-id/20090721195312.207CA75331E@cvs.postgresql.org
        regards, tom lane