Flush-to-zero mode in floating-point
Flush-to-zero mode replaces denormalized numbers with zero. This does not comply with IEEE 754 arithmetic, but in some circumstances can improve performance considerably.
Some implementations of floating-point use support code to handle denormalized numbers. The performance of such systems, in calculations involving denormalized numbers, is much less than it is in normal calculations.
Flush-to-zero mode in floating-point always preserves the sign bit.