DETROIT—General Motors Co. says efforts to manage the global computer chip shortage have worked better than expected, so its financial results will improve over previous forecasts. The company said in a statement Thursday it has made engineering changes, prioritized semiconductor use, and pulled some potential deliveries into the second quarter. So now the first-half earnings will be significantly better than forecasts it issued earlier in the year. GM had predicted a first-half pretax profit of around $5.5 billion when it released first-quarter earnings in May. The company also said it’s optimistic about the full year, but gave no further details. Shares of GM rose 3.7 percent to $61.84 in trading early Thursday, close to the stock’s 52-week high. In the first quarter, the company turned a $2.98 billion net profit as strong U.S. consumer demand and higher prices offset production cuts brought on by the chip shortage. GM previously forecast …