It existed on Lisp machines.

https://en.wikipedia.org/wiki/Lisp_machine

"Lisp Hardware Architecture: The Explorer II and beyond"

https://3e8.org/pub/scheme/doc/lisp-pointers/v1i6/p13-dussud...

"Garbage collection in a large LISP system"

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.125....

"KIM 20 : A SYMBOLIC RISC MICROPROCESSOR FOR EMBEDDED ADVANCED CONTROL "

https://www.computer.org/csdl/proceedings/easic/1990/2066/00...

The failed iAPX 432 processor from Intel also supported it.

https://en.wikipedia.org/wiki/Intel_iAPX_432#Garbage_collect...

https://news.ycombinator.com/item?id=9448712

It's something that has been researched, but not deployed. It would implement GC memory tagging in the CPU or even the memory controller. Google Scholar should produce some good hits.