Credit Suisse is cutting roughly 4,000 jobs to reduce costs after announcing a massive pre-tax loss in the fourth quarter that includes "substantial charges which are not reflective of our underlying business performance," the bank said Thursday.The Swiss banking giant posted a net loss of 5.83 billion Swiss francs ($5.8 billion), compared to a net profit 691 million francs a year earlier.It reported a pretax quarterly loss of 6.4 billion, including a 3.8-billion-franc impairment charge linked to its acquisition of Donaldson, Lufkin & Jenrette investment bank in 2000. CEO Tidjane Thiam, who took over in the summer, said the job cuts will represent savings of 1.2 billion francs per year.