[llvm-dev] [RFC] Upstream development of support for yet-to-be-ratified RISC-V extensions

[Chris Lattner via llvm-dev]

On Jan 21, 2020, at 5:00 AM, Alex Bradbury <asb at lowrisc.org> wrote:
>> This all makes sense to me.
> 
> That's correct, thanks for the feedback.
> 
> I do like the idea from James of having the compiler always spit out a
> note when enabling the experimental extension, warning of its
> experimental nature. If we had such a warning and additionally
> required a `-riscv-enable-experimental-extensions` or similar, then I
> think there could be merit in including in the ISA string as Simon
> suggests, especially as we're likely to start putting that string in
> ELF output etc.

Are you suggesting this behavior from Clang or from LLVM?  I think it would be a bad thing for LLVM to produce this warning: there isn’t a precedent for this, and it breaks the library-based design goals.  Having clang produce a warning could be done, but it would be very noisy (one warning for every .c file in a build) and I’m not sure how much value it provides.

-Chris