The bi in bipush stands for the byte integer type; the i in istore_1, iload_1, and isub stands for the 32-bit integer type. The compiler has converted the expression into an int value.

Gangnam Style overflows INT_MAX, forces YouTube to go 64-bit ... 1970. 32-bit systems use a signed 32-bit integer for this, so they will wrap around 2,147,483,647 seconds after that date.