[PATCH] D148066: [RISCV] Add Smaia and Ssaia extensions support

[Alex Bradbury via Phabricator via cfe-commits]

asb added a comment.

In D148066#4294924 <https://reviews.llvm.org/D148066#4294924>, @kito-cheng wrote:

>> My concern would be that as we don't gate CSR names on enabling the relevant extension, people could start using CSR names and encodings that could change, without opting in via -menable-experimental-extensions, perhaps not realising that they're using the unratified version. OTOH, you could argue it was user error from the start by not trying to specify all the needed extensions in the ISA naming string.
>
> We decide don't gate CSR before, but I am wondering maybe we should gate those CSR if they are defined by a unratified/experimental ext., and remove the checking once it ratified, since it might change the name or CSR number before ratified.

That's definitely a risk, but at least when people try to do the "right" thing and specify the extension name in the ISA string, they'll quickly find out that the version supported in the compiler is experimental. Given the cost of marking such CSR extensions as experimental is near-zero, I think we might as well. I agree gating the CSR names might also make sense, but then we're back to the effort of testing this. I think our conclusions before were that nobody is particularly opposed to doing finer grained control of CSRs for new extensions at least (it's more problematic for the older CSRs given spec changes to move CSRs to separate extensions), so I think it would be find if someone wanted to implement that. I don't think we need that as a pre-requisite for this patch though, IMHO.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D148066/new/

https://reviews.llvm.org/D148066