Impact

All LLVM versions since 2015 fold (xor (shl 1, x), -1) to (rotl ~1, x) if run with optimizations enabled.
Here ~1 is generated as an unsigned 64 bits number (2^64-1). This number is zero-extended to 256 bits on EraVM target while it should have been sign-extended. Thus instead of producing roti 2^256 - 1, x the compiler produces rotl 2^64 - 1, x.

In Solidity, the bug has been confirmed to be reproducible with the following pattern:

    function bug(
        uint256 data,
        uint256 index,
    ) public pure returns(uint256) {
        uint256 bit = 1 << index;
        data &= ~bit;
        return data;
    }

Analysis has shown that no contracts were affected by the date of publishing this advisory.

Patches

Fixed in version 1.5.3.

Workarounds

Upgrading and redeploying affected contracts is the only way.