Qsys:Peripherals:Frequency_counter

Found it at Qsys : Library : Peripherals : Debug and Performance : Frequency_counter"

The main source file starts with this:

// (C) 2001-2014 Altera Corporation. All rights reserved.
// Your use of Altera Corporation's design tools, logic functions and other 
// software and tools, and its AMPP partner logic functions, and any output 
// files any of the foregoing (including device programming or simulation 
// files), and any associated documentation or information are expressly subject 
// to the terms and conditions of the Altera Program License Subscription 
// Agreement, Altera MegaCore Function License Agreement, or other applicable 
// license agreement, including, without limitation, that your use is for the 
// sole purpose of programming logic devices manufactured by Altera and sold by 
// Altera or its authorized distributors.  Please refer to the applicable 
// agreement for further details.
//Frequency checker
//Author: Harold Wang
`timescale 1ns/1ns
module frequency_counter# (
    parameter CROSS_CLK_SYNC_DEPTH = 2,
    parameter REG_WIDTH = 32,
    parameter DEFAULT_MAX_CNT = 1000
)
(
    input               reset,
    input               avs_clk,
    input        avs_address,
    input               avs_write,
    input               avs_read,
    input        avs_byteenable,
    input        avs_writedata,
    output reg   avs_readdata,
    input               ref_clk,
    input               des_clk
);
    //Local parameters
 

etc.

If it's in the menu, and the code has the Altera copyright, then it sure wasn't written by me!

And, no, I didn't find it on Google or on the Altera site either. That's sort of the point. It is in the main IP library (at least on my machine, and i did not put it there, and I'm the only user), but there is zero info anywhere about using it. Looks good on paper, but reality is a completely different issue.