Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

NIOS2 HW & DIV Instructions + FPU

Hello i am in charge of designing a system that does a lot of complex sin/cos/* instructions and i need them to be fast. I am using NIOS2-F at 100mhz in a Cyclone IV. I've enabled HW and DIV ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Hmmm.... Either:

1) your nios has the fpu instructions.

2) the compiler is optimising out the arithmetic - which it can do for the above code.

3) there are no custom instructions at all, and the cpu takes an 'unknown instruction' trap, and some code emulates them. (I'm not sure this is possible at all)

Try with 'volatile float legal;' which will force the compiler to do the memory accesses.