What is the gas cost of this function?

Question

I have this contract

contract Contract {
    function a() external {
        assembly {
            return(0, 1000000)
        }
    }
}

I am calculating the gas cost for a call to a. Following https://github.com/wolflo/evm-opcodes/blob/main/gas.md#a0-1-memory-expansion, I have roughly:

gas = (1e6/32)^2/512 + (1e6/32)*3 ~ 2M

Running the transaction via hardhat returns a gas of ~4M. Why is it double? I also changed the size in the return, and confirmed the quadratic behavior, but there is this factor 2 I can't understand.

Answer 1

I tried to deploy an instance of the contract and the calculation is correct, i.e. gas used is ~2M.

The 4M is explained in this way: I was testing the contract via HardHat and deploying it via hardhat-upgrades, so with a Transparent Proxy... in this case there's a factor 2 involved as the result is copied into the proxy context after the delegatecall!

Refs: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/4e7e6e54daedf091d91f2f2df024cbb8f253e2ef/contracts/proxy/Proxy.sol#L34