Do they lack the CASA instruction with supervisor-mode ASI? What happens when the CASA instruction with user-mode ASI is executed in supervisor mode?
For all LEON3 (with CASA support) the CASA instruction works in supervisor-mode regardless of ASI used. In user-mode CASA only works with the user-mode ASI. So CASA with user-mode ASI works for both user-mode and supervisor-mode. By having user-mode ASI as default, one would not need to change flag when compiling user or kernel code.
On a few old LEON3 systems the CASA instruction only works in supervisor mode. Using the CASA instruction with the user-mode ASI on these systems is not legal and will cause a trap.
-- Daniel Cederman
