llvm dev - Sep 2019 - How to add support for ashlsi3, lshrsi3, divmodti4, and ashrsi3

First some context. I'm working on an embedded driver written in Rust, and
want it to compilable to the AVR platform, which is experimentally supported by
LLVM. When compiling, I get linker errors that complain undefined references to
these functions:
 * __ashlsi3
 * __lshrsi3
 * __divmodti4
 * __ashrsi3
The exact error and my other findings on this can be found in an issue
<https://github.com/avr-rust/rust/issues/149> on the Github repo for the
AVR Rust fork.
I've been able to confirm that these functions are present in libgcc
<https://github.com/gvz/avr-gcc/tree/master/libgcc>.

My current belief is that the first step towards rectifying the problem (based
on this comment
<https://github.com/avr-rust/rust/pull/115#issuecomment-435277273> on a
related issue) is to add support for these functions to compiler-rt. However, I
am 1) not confident that this is the correct move, and 2) completely ignorant on
how to make such an addition.

Any direction that someone familiar with this can provide would be greatly
appreciated. Without even knowing where in the code to look for where these new
functions might live makes moving forward very difficult.

Thanks!
Jonah Dahlquist
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Bumping this up. I'd be eternally grateful for any kind of direction on
this. This bug is blocking a project of mine, and I don't have any
experience with compilers to lean on. 😩

On Fri, Sep 20, 2019, at 8:32 PM, Jonah Dahlquist via llvm-dev
wrote:
> First some context. I'm working on an embedded driver written in Rust,
and want it to compilable to the AVR platform, which is experimentally supported
by LLVM. When compiling, I get linker errors that complain undefined references
to these functions:
> 
>  * __ashlsi3
>  * __lshrsi3
>  * __divmodti4
>  * __ashrsi3
> The exact error and my other findings on this can be found in an issue
<https://github.com/avr-rust/rust/issues/149> on the Github repo for the
AVR Rust fork.
> I've been able to confirm that these functions are present in libgcc
<https://github.com/gvz/avr-gcc/tree/master/libgcc>.
> 
> My current belief is that the first step towards rectifying the problem
(based on this comment
<https://github.com/avr-rust/rust/pull/115#issuecomment-435277273> on a
related issue) is to add support for these functions to compiler-rt. However, I
am 1) not confident that this is the correct move, and 2) completely ignorant on
how to make such an addition.
> 
> Any direction that someone familiar with this can provide would be greatly
appreciated. Without even knowing where in the code to look for where these new
functions might live makes moving forward very difficult.
> 
> Thanks!
> Jonah Dahlquist
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
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