faultOnNilArg1    bool      // this op will fault if arg1 is nil (and aux encodes a small offset)
	usesScratch       bool      // this op requires scratch memory space
	hasSideEffects    bool      // for "reasons", not to be eliminated.  E.g., atomic store, #19182.
	zeroWidth         bool      // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.