Start column from DebugLoc of MachineInstr

Hi,

  1. Below code gives me end column number of the machine instruction.
    How can I get the start column number ?

const MachineInstr *First;
… //First is assigned.
DebugLoc MIDB = First->getDebugLoc();
col_begin = MIDB.getCol();


If my C block is
{
int t = 10;
}
This gives me value 20, instead of 9.