[llvm] [AArch64] Add streaming-mode stack hazards. (PR #98956)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

A couple ways to possibly save some stack space:

- For FP CSRs, would it make sense to go through integer registers?  e.g. `fmov x16, d8; str x16, [sp, #16]`.  More microops, but you don't need hazard padding for the FP CSRs.  Maybe depends on how expensive the micro-ops are.
- If the hazard is related to cache-lines, realigning the stack could reduce the amount of necessary padding.

https://github.com/llvm/llvm-project/pull/98956