Difference between SHL and SAL in 80x86

According to this, they are the same:

The shift arithmetic left (SAL) and shift logical left (SHL) instructions perform the same operation; they shift the bits in the destination operand to the left (toward more significant bit locations). For each shift count, the most significant bit of the destination operand is shifted into the CF flag, and the least significant bit is cleared (see Figure 7-7 in the Intel®64 and IA-32 Architectures Software Developer'sManual, Volume 1).

Both were probably included just for completeness since there is a distinction for right-shifts.

shl and sal are the same.They have same machine code.
shr and sar are NOT the same.They have almost same machine code.(but not)
Check this.

There's no difference apart from Intel and AMD wanting to deprecate the duplicate SAL.