[llvm] [CodeGen] Distinguish zero-sized call frames from no call frame in MachineBB (PR #106964)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

> > Distinguishing between instructions in a
> > zero-sized call frame and instructions outside of call frames via the
> > call frame size info stored in the MachineBBs is helpful to avoid nested
> > CALLSEQs
> 
> Do you have an example of where this is useful?

Yes, PR #106965 (the second one in this stacked PR) relies on this for identifying locations that are inside any call frame (even zero-sized ones) to avoid nested CALLSEQs when thread-local-storage addresses are passed as a function argument.

https://github.com/llvm/llvm-project/pull/106964