By Siddarth S Aug 31 (Reuters) - Canada's main index extended gains on Thursday as a jump in Shopify shares lifted the broader technology sector, while pot firms gained after the United States' move to ease curbs on marijuana. Canadian Imperial Bank of Commerce CM.TO fell 3% after it missed analysts' estimates for quarterly profit. Separately, data showed U.S. personal consumption expenditures price index, the Federal Reserve's preferred inflation gauge, climbed 3.3% in July, on an annual basis, in line with expectations.