public RegisterValue getRegisterValue(Register reg, Address fromAddr, Address toAddr) {
		
		Varnode rvnode = getRegisterVarnodeValue(reg, fromAddr, toAddr, false);
		if (rvnode == null) {
			return null;
		}

		int spaceID = rvnode.getSpace();

		// check normal constant and suspect constants
		if (spaceID != addrFactory.getConstantSpace().getSpaceID() &&
			spaceID != SUSPECT_OFFSET_SPACEID) {
			return null;
		}

		return new RegisterValue(reg, BigInteger.valueOf(rvnode.getOffset()));
	}
Get the value of a register that was set coming from an address to an
another address.
Note: If trackStartEndState flag is false, then this will return the current value.

@param reg value of register to get
@param fromAddr location the value came from
@param toAddr location to get the value of the register coming from fromAddr

@return value of register or null
Ghidra/Features/Base/src/main/java/ghidra/program/util/VarnodeContext.java