Why llvm doesn't has the [target-independent] promote alloca from loop pass?

I know NVPTX has implemented an llvm/lib/Target/NVPTX/NVPTXAllocaHoisting.cpp pass which can promote a compile-time-known-sized alloca op from the loop to entry bb, I think it is a very common feature, why it cannot have a target-independent version？

If it can't, would you please tell me the reason, or, I will try to commit a PR implemented by me?

Start by reading llvm/lib/Target/NVPTX/NVPTXAllocaHoisting.cpp and identify the conditions under which it promotes compile-time-known-sized allocas from loops to the entry block. Compare that pass with the requirements for a target-independent implementation, then document the rationale or define the scope of a proposed change. No test file or entry point is named in the issue.

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