TM4C123 development board issue
You are missing a lot, to start with you need the following:

//
// Run from the PLL at 120 MHz.
//
g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
SYSCTL_OSC_MAIN | SYSCTL_USE_PLL |
SYSCTL_CFG_VCO_480), 120000000);


Also, the Tiva Ware package has a ton of resources, documentation, sample programs, etc etc. Including a "Hello World" bare minimum program.