Hello!

I am coding some little macros to help me out with big sources to reduce complexity. I always use some registers (mostly eax and ecx) to store some temporary data or something else. However, I always move 0 to the register, like this:
MOV eax, 0

The problem is, my code was faster before I added the move instructions, so I assume they need a little more clock cycles. What I want to ask is for a better way to reset a register to 0, as I am having 10% less the speed when using MOV.

Thanks!

it is strange that MOV is slow for you...

try this:

xor eax,eax
and eax,0ffffffffh
sub eax,eax

saigon, it's time to use 'search' option

@Ivan2k2: I tried all of them, it seems that "XOR eax, eax" is the fastest option. (And, I have too many macros to list and each of them uses MOV, so that's why it's slow)

@Vasilev: It's not time to use the search. I searched the board before posting, but the only thread I found which had good information was http://board.flatassembler.net/topic.php?t=4485 . But I had to ask, because I didn't find the really fastest option.

Thanks!

That remains EAX untouched

oops... of course 'and eax,0'

xor eax , eax is the fastest option on AMD64 because it is the shortest instruction for the task, and allows you to use the instruction cache in a better way. Besides, the register dependency (that made this method actually slower on Athlon XP) was taken out of this operation.

saigon: how about reading http://board.flatassembler.net/topic.php?t=4816 first?