public BigInteger getValue(Register register, Address fromAddr, Address toAddr, boolean signed) {
		RegisterValue value = getRegisterValue(register, fromAddr, toAddr);
		if (value == null) {
			return null;
		}
		return signed ? value.getSignedValue() : value.getUnsignedValue();
	}
Returns the future register value at the specified address that occurred because of a flow
from the fromAddr.  If no future value is stored, it will return the value stored in the program.

@param register the register to get a value for.
@param fromAddr the address from which this flow originated.
@param toAddr the future flow address to save the value.
@param signed if true, interpret the value as signed.
@return the value of the register at the location, or null if a full value is not established.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/disassemble/DisassemblerContextImpl.java