On Tue, Aug 15, 2023 at 1:38 PM MegaIng via Gcc <gcc@gcc.gnu.org> wrote: > > 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?
POINTER_SIZE needs to be only a C expression, not a constant > 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? You could look into the AVR port for example. I think libgcc should work reasonably well here. > 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" ...)`. Somebody else has to answer this. Richard. > Many thanks in advance, > > MegaIng > > > [1]: https://github.com/ETC-A/etca-spec >
