m68k support

George Nakos runs ~http://brownbot.hopto.org/~ http://brownbot.mooo.com/ which has m68k support. I asked him how he did it and he gamely had a crack at a patch for CE. He had to bail as it got a little warty but here’s his notes:

We build binutils using:

../binutils-2.27/configure --disable-multilib --disable-nls --enable-lto --prefix=/usr --target=m68k-ataribrown-elf

So, a plain binutils 2.27, nothing fancy at all. We chose the "ataribrown" name to differentiate from other versions of cross-gcc for ataris floating about. I guess you could use "unknown" so it's a bit more generic, after all there's no patching on this level at all so it should apply for all m68k based machines.

Next, we build gcc itself using:

   ../gcc-6.2.0/configure \
       --target=m68k-ataribrown-elf \
       --disable-nls \
       --enable-languages=c,c++ \
       --enable-lto \
       --prefix=/usr \
       --disable-libssp \
       --enable-softfloat \
       --disable-libstdcxx-pch \
       --disable-clocale \
       --disable-libstdcxx-threads \
       --disable-libstdcxx-filesystem-ts \
       --disable-libquadmath \
       --enable-cxx-flags='-O2 -fomit-frame-pointer -fno-threadsafe-statics -fno-exceptions -fno-rtti -fleading-underscore' \
       CFLAGS_FOR_TARGET="-O2 -fomit-frame-pointer -fno-threadsafe-statics -fleading-underscore" \
       CXXFLAGS_FOR_TARGET="-O2 -fomit-frame-pointer -fno-threadsafe-statics -fno-exceptions -fno-rtti -fleading-underscore" \
       LDFLAGS_FOR_TARGET="--emit-relocs -Ttext=0"

Most of the switches deal with switching off stuff that made compilation fail (exceptions for example, especially when building the libs).

From what I understand you don't require building any libs, right? If yes then this is pretty much it if I'm not mistaken. I've tried building it in linux mint 18 (which is ubuntu 16.06 or 16.04 - can't remember) so it should build cleanly.

[windenntw]

Hi @mattgodbolt

TLDR: Yea, you’d need to enable m68k there.

Min-Yih mentions in https://groups.google.com/g/llvm-dev/c/KH5jlTH_is4

I’m also working pretty hard recently on upstreaming Motorola M68k backend to LLVM [1], and the works are wrapping up so I might can give some advices …

Usually a new target will enter LLVM as an experimental target first (it will not be build by default unless designated by the LLVM_EXPERIMENTAL_TARGETS_TO_BUILD cmake variable) before becoming an official one. …

[windenntw]

FYI m68k has now landed in LLVM: https://github.com/llvm/llvm-project/tree/main/llvm/lib/Target/M68k