@Override
			public Long unknownValue(VarnodeContext context, Instruction instruction,
					Varnode node) {
				if (node.isRegister()) {
					Register reg = program.getRegister(node.getAddress());
					if (reg != null) {
						// never assume for flags, or control registers
						String regName = reg.getName();
						if (regName.equals("sp")) {
							return null;
						}
						if (!regName.startsWith("r")) {
							return Long.valueOf(0);
						}
					}
					if (hitTheGuard) {
						return assumeValue;
					}
				}
				if (hitTheGuard && context.isSymbol(node)) {
					return assumeValue;
				}
				return null;
			}
Check if there are any data references to this location.
@param program
@param addr
@return true if there are any data references to addr
Ghidra/Processors/ARM/src/main/java/ghidra/app/plugin/core/analysis/ArmAnalyzer.java