DIM counter32 AS integer ' 64-bit variable
DIM prevCounter32 AS integer
DIM rolloverCount AS integer
DIM extendedCounter64 AS integer

prevCounter32 = 0
rolloverCount = 0
extendedCounter64 = 0

Do
   ' Read the current 32-bit counter value
   counter32 = 'From the PIO

   ' Adjust counter32 to account for 32-bit rollover
   IF counter32 > 2147483647 THEN
       counter32 = counter32 - 4294967296 ' 2^32
   END IF

   ' Check for rollover
   IF counter32 < prevCounter32 - 2147483648 THEN
       rolloverCount = rolloverCount + 1
   ELSEIF counter32 > prevCounter32 + 2147483648 THEN
       rolloverCount = rolloverCount - 1
   END IF

   ' Update the extended 64-bit counter
   extendedCounter64 = (rolloverCount * 4294967296) + counter32

   ' Store the current counter value as the previous counter value
   prevCounter32 = counter32

   ' Output the extended counter value
   PRINT "Extended Counter: "; extendedCounter64
Loop

#include "ARMCFunctions.h"

void count64(long long int *prevCounter32, long long int *rolloverCount, long long int *extendedCounter64) { /* CSUBs use pointers */

and then a C version of your code but keep using * to deref the pointers

}

do
 Error = command - actual
 DAC = Kp * Error
 Pause 1    (it actually runs in SETTICK 1)
loop