public long getSignedValue() {
		return (value << unusedBits) >> unusedBits; // if value has highbit set, sign extend it
	}
Get the value as a signed long, where the highest bit of the value, if set, will be 
extended to fill the remaining bits of a java long.

@return signed value
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/scalar/Scalar.java