private int addStackOverride(Program prog, Address addr, int purge) {
		Integer stackDepthChange = CallDepthChangeInfo.getStackDepthChange(prog, addr);
		if (stackDepthChange == null) {
			return purge;
		}

		int extrapop = CallDepthChangeInfo.getStackDepthChange(prog, addr);
		if (purge == Function.UNKNOWN_STACK_DEPTH_CHANGE ||
			purge == Function.INVALID_STACK_DEPTH_CHANGE) {
			return extrapop;
		}
		return purge + extrapop;
	}
Modify the function purge by any stack depth override

@param prog program
@param addr addr of instruction that could have an override of the stack depth
@param purge current purge depth.
@return new purge, which includes the extrapop value
Ghidra/Features/Base/src/main/java/ghidra/program/util/SymbolicPropogator.java