[VHDL] Problem with 'event attribute on std_logic_vector signal

the problem is that

if IR'event then

is perfectly legal VHDL, which is why it compiles in ActiveHDL (this ia just a simulator and development environment). It will work perfectly fine in a simulator. an event occurs any time IR changes. When it comes to Quartus, it has to map this behaviour on to real hardware, which it cannot do, as extra circuitry is required that detects changes in IR, that is not described in the VHDL. You would usually compare a registered version of IR to the current value of IR.

Im guessing the origional designer intended it to be used in this way, but does not understand how hardware works.

Edit - just to add, are you sure this isnt a VHDL model? its quite common to use VHDL like this in models rather than synthesisable code.