Have Bashu Han people used Southwest Mandarin since ancient times?

Southwest Mandarin is a mandarin dialect gradually formed by immigrants from the Ming Dynasty and later.

It is generally believed that Southwest Mandarin is an extension of Jianghuai Mandarin, and the two should be related and belong to Southern Mandarin, but the academic circles are cautious about this formulation. Immigration is the main reason for the formation of Southwest Mandarin.

Sichuan is one of the earliest areas where Han migrated to the southwest. Sichuan was the land of Bashu in ancient times, with fertile land and peaceful geography. Han Chinese first moved here after Qin unified Bashu (about 30 BC1). From the Qin Dynasty to the Song Dynasty, the Han people moved to Sichuan to escape the war or natural disasters. For example, in the early years of the Southern Song Dynasty, due to the Huang Chao Uprising, the route of Han people moving into Sichuan was mainly crossing the Qinling Mountains, so the main immigrants were Han people from the Central Plains (mainly Shaanxi and Gansu)