[llvm] [GlobalISel][AArch64][AMDGPU] Lower FPOWI into series of multiplication (PR #95217)

[via llvm-commits]

isuckatcs wrote:

> Where do you see this optimization?

It is in [SelectionDAGBuilder.cpp](https://github.com/isuckatcs/llvm-project/blob/2ca8c856eeae739ec1e7242ee7e69f99ecf376d3/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp#L5790)

https://github.com/llvm/llvm-project/pull/95217