swift234

Re-instate: "SILPassManager: After a new function is pushed on the stack don't restart the pipeline on the old function."

This re-instates commit de9622654dfd28f7b14df0c03269d34b0b98fe31

The problem of the infinite loop should be fixed by the previous fix in FunctionSignatureOpts.
In addition this new commit implements a safety check to void such cases, even if buggy optimizations try to keep pushing new functions onto the work list.