Using nios2 system to let led display,but not success

Today, I had a nios2 system. Time in debugging, are all normal. However, when load in de2 board, not the results of operation. I would like to ask why, and how to resolve them.Thanks!:)

Next is the test programme:

# include "system.h"# include "altera_avalon_pio_regs.h"# include "alt_types.h"

int main (void) __attribute__ ((weak, alias ("alt_main")));

int alt_main (void)

{

alt_u8 led = 0x2;

alt_u8 dir = 0;

volatile int i;

while (1)

{

if (led & 0x81)

{

dir = (dir ^ 0x1);

}

if (dir)

{

led = led >> 1;

}

else

{

led = led << 1;

}

IOWR_ALTERA_AVALON_PIO_DATA(LEDG_BASE, led);

i = 0;

while (i<200000)

i++;

}

return 0;

}