[llvm] [SystemZ] Eliminate call sequence instructions early. (PR #77812)

[Ulrich Weigand via llvm-commits]

uweigand wrote:

> Do we need to support the inline-asm alignstack attribute? In that case we need to do a similar handling of INLINEASM[_BR] instructions to set the adjustsStack flag. My understanding is however that the stack is always aligned at 8 bytes and therefore this is not needed...?

I don't think this flag currently causes any special action on Z.   (But it would be good to try a few test cases to verify that!)   However, if and when that might change in the future, it wouldn't be good if the generic infrastructure around the flag is somehow broken ...

As a more general question, would we be the first platform to not use the adjuststack pseudos, or is there precedent?  If the latter, how are they handling this issue?

https://github.com/llvm/llvm-project/pull/77812