Most Significant Bit Index

msb.sol

pragma solidity ^0.8.4;

library LibBit {
    function msbPosition(uint256 value) internal pure returns(uint8 position) {
        assembly {
            // value > 2*128 - 1
            if gt(value,0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF) {
                value := shr(128,value)
                position := add(128,position)
            }
            // value > 2*64 - 1
            if gt(value,0xFFFFFFFFFFFFFFFF) {
                value := shr(64,value)
                position := add(64,position)
            }
            // value > 2*32 - 1
            if gt(value,0xFFFFFFFF) {
                value := shr(32,value)
                position := add(32,position)
            }
            // value > 2*16 - 1
            if gt(value,0xFFFF) {
                value := shr(16,value)
                position := add(16,position)
            }
            // value > 2*8 - 1
            if gt(value,0xFF) {
                value := shr(8,value)
                position := add(8,position)
            }
            // value > 2*4 - 1
            if gt(value,0xF) {
                value := shr(4,value)
                position := add(4,position)
            }
            // value > 2*2 - 1
            if gt(value,0x03) {
                value := shr(2,value)
                position := add(2,position)
            }
            // value > 2*1 - 1
            if gt(value,0x01){
                value := shr(1,value)
                position := add(1,position)
            }
        }
    }
}

            r := shl(7, lt(0xffffffffffffffffffffffffffffffff, x))
            r := or(r, shl(6, lt(0xffffffffffffffff, shr(r, x))))
            r := or(r, shl(5, lt(0xffffffff, shr(r, x))))

            x := shr(r, x)
            x := or(x, shr(1, x))
            x := or(x, shr(2, x))
            x := or(x, shr(4, x))
            x := or(x, shr(8, x))
            x := or(x, shr(16, x))

            r := or(r, byte(and(31, shr(27, mul(x, 0x07C4ACDD))), 
                0x0009010a0d15021d0b0e10121619031e080c141c0f111807131b17061a05041f))

@Vectorized awesome work. but still win solmate lib log2.