[llvm] [X86][APX] Prevent from emitting push2/pop2 if stack alignment<16B (PR #143076)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> > > Why don't set the alignment to 16B in this case?
> > 
> > 
> > There's an option to override the alignment. We should respect customer's selection.
> 
> We respected , 16B align is also 8B align

The 8B means OS can only guarantee stack is 8B aligned. In other word, it doesn't guarantee stack is always aligned to 16B under some special circumstances.

https://github.com/llvm/llvm-project/pull/143076