protected void deleteRegisterValueRange(ListingActionContext context) {
		RegisterTransitionFieldLocation location =
			(RegisterTransitionFieldLocation) context.getLocation();
		Register register = location.getRegister();
		Address addr = location.getAddress();
		ProgramContext programContext = context.getProgram().getProgramContext();
		AddressRangeIterator it = programContext.getRegisterValueAddressRanges(register);
		while (it.hasNext()) {
			AddressRange range = it.next();
			if (range.contains(addr)) {
				Command<Program> cmd = new SetRegisterCmd(register, range.getMinAddress(),
					range.getMaxAddress(), null);
				if (!tool.execute(cmd, context.getProgram())) {
					Msg.showError(this, tool.getToolFrame(), "Register Context Error",
						cmd.getStatusMsg());
				}
				return;
			}
		}
	}
Shows the registers available in a program along with any values that are set.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/register/RegisterPlugin.java