boolean isStackPointer(Varnode output) {
		if (output == null) {
			return false;
		}

		Register reg = null;
		reg = trans.getRegister(output);

		// is this register the stack pointer
		if (reg == stackReg) {
			return true;
		}

		return false;
	}
Inspect the instruction and return how it affects the stack depth. If the
depth cannot be determined, then return that the stack depth change is
unknown.

@param instr instruction to analyze
@param procContext 
@param currentStackDepth 

@return int change to stack depth if it can be determined,
        Function.UNKNOWN_STACK_DEPTH_CHANGE otherwise.
Ghidra/Features/Base/src/main/java/ghidra/app/cmd/function/CallDepthChangeInfo.java