Also, I found the PIP process to be overly dramatized relative to my experience. I had a PIP imposed on me a couple years before I willingly left, and I "graduated" out of it with support and cooperation of my manager. Everyone involved seemed to want me to succeed.
Also, when I left, I opted into a second PIP, because HR and my manager wanted me to leave on good terms. Doing so let me get severance while quitting (it was ~3 months worth based on my 5+ year tenure). I'm not sure if this option still works though.