Function:

Finds the first (lowest) bit set to 1 in op2, sets ZF=1 and returns the bit
position in op1. If op2 is 0, ZF=0 and the value of op1 is undetermined,
some 386's leave the old value in op1, some early 486's load garbage into
op1 and later 486's leave op1 unchanged.




BSWAP reg32   Byte Swap
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