# Storage read optimization

**URL:** <https://forum.soliditylang.org/t/storage-read-optimization/1258>\
**Category:** Feedback\
**Created:** [October 4, 2022, 2:52pm UTC](https://forum.soliditylang.org/t/storage-read-optimization/1258 "2022-10-04T14:52:13Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![sakulstra](https://sea1.discourse-cdn.com/flex001/user_avatar/forum.soliditylang.org/sakulstra/32/707_2.png) [@sakulstra](https://forum.soliditylang.org/u/sakulstra)\
**Post date:** [October 4, 2022, 2:52pm UTC](https://forum.soliditylang.org/t/storage-read-optimization/1258/1 "2022-10-04T14:52:14Z")

</div>

Hello, I recently got feedback on a smartcontract to locally cache storage values inside variables to save some gas.

Before:

```auto
  function getTotalClaimableRewards() external view override returns (uint256) {
    if (address(_rewardToken) == address(0)) {
      return 0;
    }

    address[] memory assets = new address[](1);
    assets[0] = address(_aToken);
    uint256 freshRewards = _incentivesController.getUserRewards(
      assets,
      address(this),
      address(_rewardToken)
    );
    return _rewardToken.balanceOf(address(this)) + freshRewards;
  }

```

After:

```auto
  function getTotalClaimableRewards() external view override returns (uint256) {
    address rewardToken = address(_rewardToken); // local caching of storage
    if (rewardToken == address(0)) {
      return 0;
    }

    address[] memory assets = new address[](1);
    assets[0] = address(_aToken);
    uint256 freshRewards = _incentivesController.getUserRewards(
      assets,
      address(this),
      rewardToken
    );
    return IERC20(rewardToken).balanceOf(address(this)) + freshRewards;
  }

```

I was super surprised to see that this actually has meaningful effects on the functions gas consumption. Shouldn’t it be relatively easy for the compiler to optimize this? I would assume static code analysis could easily detect that:

1. `rewardToken` isn’t mutated
2. there’s space left on the stack

What’s the reason for not optimizing this away in the compiler?  
(Tested on solc `Version: 0.8.10+commit.fc410830.Linux.g++`)