Garlic at high heat? Does it get bitter?

I'm doing a couple of choice rib roasts today, and wanted to include some mashed garlic in my slather/rub on the outside of the roasts. Something in the back of my mind says that using garlic like this (in a 350-400 degree smoker) can get the garlic tasting bitter. But I don't know where I picked this up and whether it has any truth.

Any concern to using mashed garlic like this

Thanks. I ended up just adding some garlic powder to the slather. I've certainly had garlic powder in just about every rub I've put together myself.

Roasts are in and the countdown to dinner has commenced!