[clang] [llvm] [mlir] [NVPTX] Add support for Shared Cluster Memory address space. (PR #135444)

[Artem Belevich via llvm-commits]

================
@@ -25,6 +25,7 @@ enum AddressSpace : unsigned {
   ADDRESS_SPACE_CONST = 4,
   ADDRESS_SPACE_LOCAL = 5,
   ADDRESS_SPACE_TENSOR = 6,
+  ADDRESS_SPACE_SHARED_CLUSTER = 7,
----------------
Artem-B wrote:

PTX docs say:
```
 If no sub-qualifier is specified with the .shared state space, then it defaults to ::cta.
```

Ideally, it's the most generic variant that should've had the most generic name of `shared`, and the specific subsets would have an additional suffix, but `shared` already has 10+ years of being in use. For pretty much all existing users SHARED already means a per-CTA variant, and I think we should keep it as is.  Changing its name to something else will not really buy us anything other than churn, IMO.

We may consider adding SHARED_CTA as an alias to SHARED. I can see how in some new contexts it may be useful to highlight the intended distinction.



https://github.com/llvm/llvm-project/pull/135444