[llvm] [RISCV] Deduplicate frame base address materializations for large stack frames (PR #211748)

[Pengcheng Wang via llvm-commits]

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wangpc-pp wrote:

I don't know if `PseudoAddLUI`/`PseudoAddUpperImm` would be a better/more descriptive name. `UI` confuses me as it looks like "User Interface".

https://github.com/llvm/llvm-project/pull/211748