On Sat, Aug 03, 2002 at 12:07:30PM -0400, Ken Fox wrote: > Nicholas Clark wrote: > >It seems that foo & (foo - 1) is zero only for a power of 2 (or foo == 0) > >but is there a fast way once you know that foo is a power of 2, to find out > >log2 foo?
The ARM doesn't have a find first set bit instruction ? This code includes 3 different ways of finding log2. http://www.ddj.com/ftp/2001/2001_07/aa0701.txt I believe the LOOKUP method was the fastest for me on SPARC, if I recall correctly. -- Jason
