public MaskedLong signExtend() {
		int bits = 64 - Long.numberOfLeadingZeros(this.msk);
		return signExtend(bits);
	}
Sign extend the masked value, according to its mask, to a full long

<p>
The leftmost defined bit is taken as the sign bit, and extended to the left.

@return the sign-extended masked long
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/expr/MaskedLong.java