When to use flush-to-zero mode in Advanced SIMD
You can change between flush-to-zero mode and normal mode, depending on the requirements of different parts of your code.
You must select flush-to-zero mode if all the following are true:
- IEEE 754 compliance is not a requirement for your system.
- The algorithms you are using sometimes generate denormalized numbers.
- Your system uses support code to handle denormalized numbers.
- The algorithms you are using do not depend for their accuracy on the preservation of denormalized numbers.
- The algorithms you are using do not generate frequent exceptions as a result of replacing denormalized numbers with 0.
You select flush-to-zero mode in one of the following ways:
- In A32 code, by setting the FZ bit in the FPSCR to 1. You
do this using the
- In A64 code, by setting the FZ bit in the FPCR to 1. You do
this using the
You can change between flush-to-zero and normal mode at any time, if different parts of your code have different requirements. Numbers already in registers are not affected by changing mode.