[Bug middle-end/121341] New: function_ok_for_sibcall should return return a string on why the target does not allow the sibcall

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121341

            Bug ID: 121341
           Summary: function_ok_for_sibcall should return return a string
                    on why the target does not allow the sibcall
           Product: gcc
           Version: 14.2.0
            Status: UNCONFIRMED
          Keywords: diagnostic, tail-call
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Forwarded from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121159#c23 .

Right now the error message for musttail just says:
```
target is not able to optimize the call into a sibling call
```

But the target should be able to explain why it can't do the sibcall.