Promotion during Green card filing

[SRD87]

I am right now on H1b visa and my company has filed my PERM few months back. It's still with Department of Labor for processing. My company is planning to promote me and I understand that would require a new PERM filing. What would be the earliest I can get promoted and not lose my priority date. I got to know that I can be promoted once my i140 is approved and company can refile my PERM with new job title and I can get my earlier assigned priority date as well. Is that correct?

Any guidance is appreciated. Thank you!!