[llvm] [PowerPC][AIX] Specify pointer info and alignment for stack store (PR #144526)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> There is also getTransientStackAlign which I've never understood

In addition to the normal stack alignment, which is only enforced at ABI boundaries, some targets specify the stack pointer register must always contain a value with a certain alignment.  For example, on AArch64, if you try to write a value that isn't 16-byte aligned, the instruction faults.

https://github.com/llvm/llvm-project/pull/144526