Background I am writing a custom, globalISel only, backend for a currently unsupported processor. I have progressed to the point where I can run
> clang -target xxx -emit-llvm file.c
> llc -march=xxx -global-isel -stop-after=irtranslator file.ll -o -
> llc -march=xxx -global-isel -debug-only=instruction-select,xxx-gisel file.ll -o -
and it will produce valid target assembly.
Problem However, when I try to run this through the clang driver:
clang -fglobal-isel --target=xxx -S file.c
I get:
error: unable to interface with target machine
Debugging I am not sure how to resolve this. The error comes directly from BackendUtils.cpp, where my target does not seem to implement TargetMachine→addPassesToEmitFile(). And as expected, when I manually override this method, the error goes away, however the assembly file is empty (as no passes have been added). However, other backends do not seem to override this, as I believe the passes (IRTranslator, RegBankSelect, etc…) get called automatically.
One thing I have not done is implement xxx.cpp in clang/lib/CodeGen/Targets/. Am am not confident I understand the purpose of the logic in here. It seems to be defining the ABI and calling conventions. My issue is I think I have already done that in llvm/Target/XXX/XXXCallingConvention.td and llvm/Target/XXX/GlobalISel/XXXCallLowering.cpp
I am not sure if this is a relevant problem, nor if it is necessary for me to do. Is this truly duplicate logic or is it necessary information for both clang and llvm.
Conclusion I understand this is quite a specific question, and I have far-from included all the relevant details. I am happy to provide anything that would be helpful. Any assistance would be greatly appreciated, thank you.
