DONE I have done up to step 15 and I am calling it a success. I have learned enough about writing the GCC backend to get started on the or1k backed. Therefore I am abondoning this port.
This is the port of the dummy architecture smh. This is done following the 21 patches series for ggx which became moxie.
- See: http://atgreen.github.io/ggx/
- See: http://stffrdhrn.github.io/software/embedded/openrisc/2018/02/03/openrisc_gcc_rewrite.html
- See: https://github.com/stffrdhrn/binutils-gdb/tree/smh-port
Here I used the latest GCC so the patches are quite a bit different in places. I will try to keep notes of the differences below.
The original patches for ggx are pretty old now and using many deprecated
API's. This required significant updates, but it was a good exercise in understanding the dependencies
of a GCC back-end.
Also, current GCC builds run a series of self tests which do not allow abort()
definitions. This means the original patch 11 does not build completely. I am
getting a
failure I
hope this improves going forward.
- Using name
SMHinstead of ggx. - Update
gcc/config.gcctoo - Not using Old Constraints
in
smh.h - Renovate poison
HARD_REGNO_MODE_OKtoTARGET_HARD_REGNO_MODE_OK - Renovate poison
HARD_REGNO_NREGStoTARGET_... - Renovate poison
MODES_TIEABLE_PtoTARGET_... - Renovate poison
LEGITIMATE_CONSTANT_PtoTARGET_... - Renovate poison
FRAME_POINTER_REQUIREDtoTARGET_... - Removed poison
RETURN_POPS_ARGS, depend on default - Removed poison
TRULY_NOOP_TRUNCATION, depend on default - Redefine
INITIALIZE_TRAMPOLINEasTARGET_TRAMPOLINE_INIT - Renovate
GO_IF_MODE_DEPENDENT_ADDRESStoTARGET_LEGITIMATE_ADDRESS_P - Define
noprequired - Define
ELIMINAL_REGSrequired - Define
INITIAL_ELIMINATION_OFFSETrequired - Don't use
abort()forTARGET_macros. for now don't define to get default implementation. - Remove
CLASS_MAX_NREGSdefinition as default implementation is the same.
It works and also selftests now pass.
- Dont define
LEGITIMATE_CONSTANT_Pas its default is true and we needTARGET_...now anyway. - Define
INITIAL_ELIMINATION_OFFSETcopied from Moxie - Define
machine_functionneeded forINITIAL_ELIMINATION_OFFSET - Added include for
gt-smh.hwhich is needed with option_override
../../local/bin/smh-elf-run -t start
insn: # 0x0000107c: $sp = 0x30000
insn: # 0x00001082: $fp = 0x0
insn: # 0x00001088: jsra 0x1074
insn: # 0x00001074: $r0 = 0x555
insn: # 0x0000107a: ret (to 0x108e)
insn: SIGILL1
program stopped with signal 4 (Illegal instruction).
- Use
TARGET_CAN_ELIMINATEinstead of poisonCAN_ELIMINATE - Define Fake
FPandAGregisters differently
Had more issues, currently prologue/epilogue do not generate push and pop instructions for some reason. However, moving on.