[PATCH] D145539: [llvm/Target] Add Windows COFF support for RISC-V

[Jessica Clarke via Phabricator via llvm-commits]

jrtc27 added a comment.

In D145539#4176834 <https://reviews.llvm.org/D145539#4176834>, @luojia wrote:

> In D145539#4176831 <https://reviews.llvm.org/D145539#4176831>, @jrtc27 wrote:
>
>> In D145539#4176824 <https://reviews.llvm.org/D145539#4176824>, @luojia wrote:
>>
>>> In D145539#4176791 <https://reviews.llvm.org/D145539#4176791>, @jrtc27 wrote:
>>>
>>>> I'm guessing this is so you can llvm-objcopy an ELF into a PE/COFF?.. Because without relocations being defined you can't do much else of use...
>>>
>>> Yes llvm-objcopy can do this and this is the current approach on EDK2 RISC-V. But for languages like Rust it will be more convenient if the compiler backend writes it out directly from build target configuration
>>
>> And how are you going to do that without a full PE/COFF specification for RISC-V?
>
> Thanks for mentioning! If I am correct, PE/COFF specification has definitions of machine architecture in headers. In this part PE/COFF included RISC-V architecture types. It does not provide relocation types on RISC-V, so for now PE/COFF specification allows us to emit RISC-V COFF binaries without any relocations. This could be a use case for RISC-V UEFI applications where it's mainly statically linked without any relocations. If there are more demands on RISC-V PE/COFF which need relocations, the current PE/COFF specification will not support them and LLVM (after this patch) would raise fatal error instead.
>
> I have limited information about RISC-V PE/COFF support as well; I don't know if other reviewers have different opinion about this part.

Well, you can't produce intermediate object files without relocations, and LLD can't read in an ELF and produce a PE/COFF, so I'm still not sure how static linking helps avoid the need for llvm-objcopy...


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