help on left-shift

[Michael Hayes]

Ming Ouyang writes:
 > Hi all,
 > 
 > Our cpu's new insns will handle logic left-shift and arithmatic left-shift
 > in differents way (a<<b, b can be negative).

Could you explain how they are different?  Conceptually they generate
the same result.  Does both your logical and arithmetic shift
instructions allow negative shift arguments?  If so look at c4x.md
as an example of how this can be handled.

Michael