official-stockfish/Stockfish — pull request #132 by mstembera (2014-11-24 23:04:12+00:00)
Title: Bitbase index() from ADD to OR.  No functional change.

I initially wrote this as a speed optimization but because Intel has done a great job making the ADD instruction with carry as fast as a bitwise OR it is exactly the same speed. I'm submitting it anyway because from a purist point of view the bitwise OR better reflects that the index is a series of bitfields as documented in the comment section instead of a number arrived at through an algebraic expression. Also it might still be faster on more primitive architectures. I realize this is very nit picky so if you don't like it just close the pull request. No functional change.