How many ways to set a register to zero?

Question

I\'m curious how many ways are there to set a register to zero in x86 assembly. Using one instruction. Someone told me that he managed to find at least 10 ways to do it.

Answer 1

This thread is old but a few other examples. Simple ones:

xor eax,eax

sub eax,eax

and eax,0

lea eax,[0] ; it doesn't look "natural" in the binary

More complex combinations:

; flip all those 1111... bits to 0000
or  eax,-1  ;  eax = 0FFFFFFFFh
not eax     ; ~eax = 0

; XOR EAX,-1 works the same as NOT EAX instruction in this case, flipping 1 bits to 0
or  eax,-1  ;  eax = 0FFFFFFFFh
xor eax,-1  ; ~eax = 0

; -1 + 1 = 0
or  eax,-1 ;  eax = 0FFFFFFFFh or signed int = -1
inc eax    ;++eax = 0