public MaskedLong signExtend(int n) {
		long newMsk = signExtend(this.msk, n);
		long newVal = signExtend(this.val, n);
		return fromMaskAndValue(newMsk, newVal);
	}
Sign extend the masked value as if of the given size in bits, to a full long

@param n the number of bits to take (right-to-left)
@return the sign-extended masked long
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/expr/MaskedLong.java