Chris Angelico <ros...@gmail.com>: > On Sat, Jul 21, 2018 at 1:14 AM, Grant Edwards > <grant.b.edwa...@gmail.com> wrote: >> I refuse to believe there's an extant processor in common use where >> an ADD is faster than an OR unless somebody shows me the processor >> spec sheet. > > "Faster than"? I'd agree with you. But "as fast as"? I believe that's > how most modern CPUs already operate. (Well, mostly.) There are > sophisticated methods of daisy-chaining the carry bit that mean the > overall addition can be performed remarkably quickly, and the end > result is a one-clock ADD operation, same as OR. For most data, most > code, and most situations, integer addition is exactly as fast as > integer bit shift.
I'm guessing the clock speed is adjusted for the longest propagation delays. According to <URL: https://en.wikipedia.org/wiki/Carry-lookahead_adder#Implementa tion_details> the maximal gate delay of a 16-bit carry-lookahead-adder is 8 gate delays. A 64-bit addition results in some more delay: <URL: https://en.wikipedia.org/wiki/Lookahead_carry_unit#64-bit_adder> Marko -- https://mail.python.org/mailman/listinfo/python-list
