So I must update my XC8 compiler to resolve this warning.
No, you are getting that warning because you DO have a newer compiler.
Later upgrades will NOT remove it.
It is just an advisory, letting you know about something that XC8 has always done, but did not previously tell you it was doing it.
It happens when you call a non-re-entrant function from both non-interrupt code, AND from inside an interrupt service.
Because XC8 uses a "compiled stack", it must create a second version of the function to handle this.
It can be useful to review your program logic, and determine if it really is necessary to call it at both levels.
Often it is an indication that you are trying to do too much inside an ISR.
Once again, it is NOT an error, just an advisory.