Hello everyone,
I am currently in the process of porting gcc to an ISA I designed with a
few others (spec [1]). Using the old ggx/moxie tutorial as a guideline
and looking at the source of other backends, as well as the quite decent
gccint document, I managed to get basic programs running (binutils,
especially gas, was also not too hard to get running). I am now
partially writing here because the gccint documents tells me to do this
(I am unsure if our project will ever be mature enough to be added to
gcc, but I don't think it hurts to strive for that), and partially
because I do need a bit of help with some stuff that I can't find
documentation for.
One of the big challenges I am facing is that for our backend we
sometimes support 16bit as the max size a CPU supports, including for
pointers, and sometimes 32bit or 64bit. Am I seeing it correctly that
POINTER_SIZE has to be a compile time constant and can therefore not
easily be changed by the backend during compilation based on command
line arguments?
Also, on another backend I saw comments relating to libgcc (or newlib?)
not working that well on systems where int is 16bit. Is that still true,
and what is the best workaround?
And a bit more concrete with something I am having a hard time
debugging. I am getting errors `invalid_void`, seemingly triggered by an
absent of `gen_return` when compiling with anything higher than -O0. How
do I correctly provide an implementation for that? Or disable it's
usage? Our epilogue is non-trivial, and it doesn't look like the other
backends use something like `(define_insn "return" ...)`.
Many thanks in advance,
MegaIng
[1]: https://github.com/ETC-A/etca-spec
