[llvm] [SelectionDAG] Freeze dynamic vector indices lowered through the stack (PR #225031)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

```
Failed Tests (4):
LLVM :: CodeGen/NVPTX/f32x2-instructions.ll
LLVM :: CodeGen/NVPTX/i32x2-instructions.ll
LLVM :: CodeGen/NVPTX/insertelt-dynamic.ll
LLVM :: CodeGen/WebAssembly/vector-extract-last-active.ll
```

https://github.com/llvm/llvm-project/pull/225031