First, compiling with -o3 (or less) instead of -o4 will avoid the problem. Second, making g_sys_opmode volatile does indeed work around the problem. Since the "volatile" qualifier tells the compiler that something is modifying the variable outside the compiler's view, that's exactly what is needed to keep it from being assumed constant. Third, removing the asm() from main.c will work around the problem, by including main.c in the recompilation. I modified EINT/DINT and EALLOW/EDIS macros in F2806x_Device.h and two cpu.h files, making them use the intrinsics __enable_interrupts, __disable_interrupts, __eallow, and __edis. As it happens, __enable_interrupts and __disable_interrupts control both INTM and DBGM, while the macros control them individually, so this may not be a completely satisfactory solution.