Intel (and most CPUs really) have had a "shadow" call stack for ret+call prediction (the Return Stack Buffer) decades before they had the control-flow integrity shadow stack. It is possible that the two stacks are now unified, but I'm not 100% sure.
The RSB has 10 or so entries and it is in the critical path, while the integrity stack might be larger and have less strict performance characteristics, so they might be separate objects.
The RSB has 10 or so entries and it is in the critical path, while the integrity stack might be larger and have less strict performance characteristics, so they might be separate objects.