assembly - Adding values without sign-extension? -


i know cpu doesn't care sign bit, because of two's complement. when using different operand sizes, source value gets sign extended destination's size.

xor rax, rax add rax, byte 0xad ; adds 0xffffffffffffffad rax 

is there an add instruction adds values without sign-extension (and avoids null bytes)?

(i'm working x86_64 architecture)


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