[clang] [CIR] Upstream ArraySubscriptExpr from function parameter with pointer base (PR #135493)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

This seems reasonable to me, but also kinda short :)  I fear it is missing stuff, so I want to let @andykaylor et-all do a final review.

https://github.com/llvm/llvm-project/pull/135493