The instruction-precise, or asynchronous, unwind tables usually take up much more space than the synchronous ones. If a user is concerned about the load size of the program and does not need the features provided with the asynchronous tables, the compiler should be able to generate the more compact variant.
This patch changes the generation of CFI instructions for these cases so that they all come in one chunk in the prolog; it emits only one .cfi_def_cfa* instruction followed by .cfi_offset ones after all stack adjustments and register spills, and avoids generating CFI instructions in the epilog(s) as well as any other exceeding CFI instructions like .cfi_remember_state and .cfi_restore_state. Effectively, it reverses the effects of D111411 and D114545 on functions with the uwtable(sync) attribute. As a side effect, it also restores the behavior on functions that have neither uwtable nor nounwind attributes.
.cfi_def_cfa_offset 32 move like this seems unnecessary. It degrades precision without reducing the number of CFI instructions for sync.