uniswap getTickAtSqrtPrice 方法解析

先上代码：

    function getTickAtSqrtPrice(uint160 sqrtPriceX96) internal pure returns (int24 tick) {
        unchecked {
            // Equivalent: if (sqrtPriceX96 < MIN_SQRT_PRICE || sqrtPriceX96 >= MAX_SQRT_PRICE) revert InvalidSqrtPrice();
            // second inequality must be >= because the price can never reach the price at the max tick
            // if sqrtPriceX96 < MIN_SQRT_PRICE, the `sub` underflows and `gt` is true
            // if sqrtPriceX96 >= MAX_SQRT_PRICE, sqrtPriceX96 - MIN_SQRT_PRICE > MAX_SQRT_PRICE - MIN_SQRT_PRICE - 1
            if ((sqrtPriceX96 - MIN_SQRT_PRICE) > MAX_SQRT_PRICE_MINUS_MIN_SQRT_PRICE_MINUS_ONE) {
                InvalidSqrtPrice.selector.revertWith(sqrtPriceX96);
            }

            uint256 price = uint256(sqrtPriceX96) << 32;

            uint256 r = price;
            uint256 msb = BitMath.mostSignificantBit(r);

            if (msb >= 128) r = price >> (msb - 127);
            else r = price << (127 - msb);

            int256 log_2 = (int256(msb) - 128) << 64;

            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(63, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(62, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(61, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(60, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(59, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(58, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(57, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(56, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(55, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(54, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(53, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))
                let f := shr(128, r)
                log_2 := or(log_2, shl(52, f))
                r := shr(f, r)
            }
            assembly ("memory-safe") {
                r := shr(127, mul(r, r))