mov [reg32], 0 or and [reg32], 0?

[hutch--]

You will probably find that at the bit level a copy bit occurs at about the same speed as a modify bit so if the source is an immediate in both, they should take a similar amount of time if they have similar circuitry in hardware.

[azdps]

Code Select Expand

Intel(R) Atom(TM) CPU N475   @ 1.83GHz (SSE4)
430     cycles for 100*mov, loop
424     cycles for 100*and, loop
412     cycles for 100*mov, REP
407     cycles for 100*and, REP

424     cycles for 100*mov, loop
424     cycles for 100*and, loop
410     cycles for 100*mov, REP
411     cycles for 100*and, REP



[Rockoon]

AMD Phenom(tm) II X6 1055T Processor (SSE3)
308     cycles for 100*mov, loop
208     cycles for 100*and, loop
88      cycles for 100*mov, REP
146     cycles for 100*and, REP
696     cycles for 100*inc, loop
695     cycles for 100*inc, REP

207     cycles for 100*mov, loop
307     cycles for 100*and, loop
88      cycles for 100*mov, REP
146     cycles for 100*and, REP
695     cycles for 100*inc, loop
695     cycles for 100*inc, REP