[RFC] Project Hand In Hand (LLVM-libc/libc++ code sharing)

[cor3ntin]

@michaelrj-google

I think sharing the math functions would be great, this proposal is focused on libc++ to keep it simple but I expect that we’ll extend this more in the future.

Thanks, this answer my question

@michaelrj-google

As for using this in clang, there’s only one concern I have: We support a much narrower range of targets than LLVM as a whole does. Right now we only support x86_64, arm64/32, and RISC-V 64/32. I think the generic implementations of math functions would work on other targets (@lntue may have some comments) but these are the ones we currently test for accuracy/speed. Do you have a list of hosts the clang frontend has to support?

I don’t think we want to derail too much the discussion here (sorry for that).
But in general, clang will not care deeply about speed, but accuracy is important. My hope would be that the generic implementation would be fine. As other have pointed out, we would want to use the same type width as the target platform, be independent of the host, and of the target rounding mode. It’s unclear to me how we will achieve all of that, but in the absence of a licence friendly GMP equivalent, I just wanted you to be aware of potential needs beyond libc++. Thanks!