6502/65816 compatible target for LLVM.


CAVEATS

This is a *very* unstable, alpha version target.

For now, the target can output only to the library object format used
by WLA DX (WLAK). The target has been tested only on SFC (SNES)
emulators and hardware.

The "standard libraries" consist of a set of assembly routines that
need to be linked externally. See arith.s and shift.s in the SFC
example: https://github.com/Peppar/llvm-C65-sfc-example


BUILDING

Steps roughly based on https://llvm.org/docs/GettingStarted.html

1. Relative paths specified are important!

2. Check out the modified LLVM

git clone https://github.com/Peppar/llvm-C65-llvm.git llvm

3. Check out the target

cd llvm/lib/Target
git clone https://github.com/Peppar/llvm-C65.git C65

4. Check out the modified Clang

cd llvm/tools
git clone https://github.com/Peppar/llvm-C65-clang.git clang

5. Configure and build LLVM and Clang

mkdir build
cd build

cmake /path/to/llvm/src -DLLVM_TARGETS_TO_BUILD="X86;C65"
cmake --build .


TESTING

Using the target to compile an SFC (SNES) "game":

https://github.com/Peppar/llvm-C65-sfc-example


TROUBLESHOOTING

If you run out of memory while linking a Debug build of clang,
try using the "gold" linker from GNU Binutils.

https://www.gnu.org/software/binutils/

If you want to debug clang with gdb, you need to execute the following
commands for breakpoints to work consistently:

set follow-fork-mode child