if arm64SpecialOperand == nil {
		// Generate the mapping automatically when the first time the function is called.
		arm64SpecialOperand = map[string]arm64.SpecialOperand{}
		for opd := arm64.SPOP_BEGIN; opd < arm64.SPOP_END; opd++ {
			arm64SpecialOperand[opd.String()] = opd
		}

		// Handle some special cases.
		specialMapping := map[string]arm64.SpecialOperand{