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

[Philip Reames via Phabricator via cfe-commits]

reames 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.

I think I agree with Kito here.  Requiring gating for experimental extensions even if we don't gate ratified ones seems like a good way to address the issue of name collision risk in experimental extensions.

I'm less concerned about number reassignment.  I'm most concerned that the same name might be reused across two extensions in a mutually incompatible way.  This would clearly get fixed before both were ratified, but well, the entire point of experimental is that they not yet ratified.


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