assembly language in the nios ii ide

Failure to open macros.s is a problem with the list of directories passed to gcc (acting as cpp) as -I dir_name.

I've no idea what is in it - but I don't think your little file relies on any of it.

You'll cut out a lot of the library code that gets added by the build it you call your function alt_main (not main).

Also, as is mentioned earlier in this thread, if you aren't using any of the Altera BSP or libc functions, you don't need any of their setup code. The only initialisation required before jumping into C code is to set %sp and %gp. For your two instruction loop even those aren't needed.