Optimize absTick calculation in TickMath.getSqrtPriceAtTick (#663)

* Optimize `absTick` calculation in `TickMath.getSqrtPriceAtTick` The getSqrtPriceAtTick function in the TickMath library has been refactored with a more efficient assembly implementation. This optimization significantly reduces the gas usage by using bitwise operations for computing absolute value of a tick. * Add test case for `getSqrtPriceAtTick` with `type(int24).min` The new test case asserts that the function `getSqrtPriceAtTick` throws an error when called with the minimum valid input. This ensures that the function behaves as expected for all possible input values, enhancing the overall test coverage. * Add comments about rounding in `getSqrtPriceAtTick`
Uniswap · May 21, 2024 · fa5164a · fa5164a
1 parent 2b87b1e
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diff --git a/.forge-snapshots/TickMathGetSqrtPriceAtTick.snap b/.forge-snapshots/TickMathGetSqrtPriceAtTick.snap
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diff --git a/.forge-snapshots/TickMathGetTickAtSqrtPrice.snap b/.forge-snapshots/TickMathGetTickAtSqrtPrice.snap
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diff --git a/.forge-snapshots/add liquidity to already existing position with salt.snap b/.forge-snapshots/add liquidity to already existing position with salt.snap
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diff --git a/.forge-snapshots/addLiquidity CA fee.snap b/.forge-snapshots/addLiquidity CA fee.snap
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diff --git a/.forge-snapshots/addLiquidity with empty hook.snap b/.forge-snapshots/addLiquidity with empty hook.snap
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diff --git a/.forge-snapshots/addLiquidity with native token.snap b/.forge-snapshots/addLiquidity with native token.snap
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diff --git a/.forge-snapshots/create new liquidity to a position with salt.snap b/.forge-snapshots/create new liquidity to a position with salt.snap
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diff --git a/.forge-snapshots/initialize.snap b/.forge-snapshots/initialize.snap
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diff --git a/.forge-snapshots/poolManager bytecode size.snap b/.forge-snapshots/poolManager bytecode size.snap
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diff --git a/.forge-snapshots/removeLiquidity CA fee.snap b/.forge-snapshots/removeLiquidity CA fee.snap
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diff --git a/.forge-snapshots/removeLiquidity with empty hook.snap b/.forge-snapshots/removeLiquidity with empty hook.snap
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diff --git a/.forge-snapshots/removeLiquidity with native token.snap b/.forge-snapshots/removeLiquidity with native token.snap
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diff --git a/.forge-snapshots/simple addLiquidity second addition same range.snap b/.forge-snapshots/simple addLiquidity second addition same range.snap
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diff --git a/.forge-snapshots/simple removeLiquidity.snap b/.forge-snapshots/simple removeLiquidity.snap
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diff --git a/.forge-snapshots/simple swap with native.snap b/.forge-snapshots/simple swap with native.snap
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diff --git a/.forge-snapshots/simple swap.snap b/.forge-snapshots/simple swap.snap
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diff --git a/.forge-snapshots/swap CA fee on unspecified.snap b/.forge-snapshots/swap CA fee on unspecified.snap
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diff --git a/.forge-snapshots/swap against liquidity with native token.snap b/.forge-snapshots/swap against liquidity with native token.snap
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diff --git a/.forge-snapshots/swap against liquidity.snap b/.forge-snapshots/swap against liquidity.snap
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diff --git a/.forge-snapshots/swap burn native 6909 for input.snap b/.forge-snapshots/swap burn native 6909 for input.snap
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diff --git a/.forge-snapshots/swap mint native output as 6909.snap b/.forge-snapshots/swap mint native output as 6909.snap
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diff --git a/.forge-snapshots/swap mint output as 6909.snap b/.forge-snapshots/swap mint output as 6909.snap
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diff --git a/.forge-snapshots/swap skips hook call if hook is caller.snap b/.forge-snapshots/swap skips hook call if hook is caller.snap
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diff --git a/.forge-snapshots/swap with dynamic fee.snap b/.forge-snapshots/swap with dynamic fee.snap
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diff --git a/.forge-snapshots/swap with hooks.snap b/.forge-snapshots/swap with hooks.snap
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diff --git a/.forge-snapshots/swap with lp fee and protocol fee.snap b/.forge-snapshots/swap with lp fee and protocol fee.snap
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diff --git a/.forge-snapshots/swap with return dynamic fee.snap b/.forge-snapshots/swap with return dynamic fee.snap
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diff --git a/.forge-snapshots/update dynamic fee in before swap.snap b/.forge-snapshots/update dynamic fee in before swap.snap
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diff --git a/src/libraries/TickMath.sol b/src/libraries/TickMath.sol
@@ -46,7 +46,15 @@ library TickMath {
     /// at the given tick
     function getSqrtPriceAtTick(int24 tick) internal pure returns (uint160 sqrtPriceX96) {
         unchecked {
-            uint256 absTick = tick < 0 ? uint256(-int256(tick)) : uint256(int256(tick));
+            uint256 absTick;
+            assembly {
+                // mask = 0 if tick >= 0 else -1
+                let mask := sar(255, tick)
+                // If tick >= 0, |tick| = tick = 0 ^ tick
+                // If tick < 0, |tick| = ~~|tick| = ~(-|tick| - 1) = ~(tick - 1) = (-1) ^ (tick - 1)
+                // Either case, |tick| = mask ^ (tick + mask)
+                absTick := xor(mask, add(mask, tick))
+            }
             if (absTick > uint256(int256(MAX_TICK))) revert InvalidTick();
 
             uint256 price =
@@ -78,6 +86,8 @@ library TickMath {
                 // this divides by 1<<32 rounding up to go from a Q128.128 to a Q128.96.
                 // we then downcast because we know the result always fits within 160 bits due to our tick input constraint
                 // we round up in the division so getTickAtSqrtPrice of the output price is always consistent
+                // `sub(shl(32, 1), 1)` is `type(uint32).max`
+                // `price + type(uint32).max` will not overflow because `price` fits in 192 bits
                 sqrtPriceX96 := shr(32, add(price, sub(shl(32, 1), 1)))
             }
         }

diff --git a/test/libraries/TickMath.t.sol b/test/libraries/TickMath.t.sol
@@ -45,6 +45,11 @@ contract TickMathTestTest is Test, JavascriptFfi, GasSnapshot {
         assertEq(maxTick, MAX_TICK);
     }
 
+    function test_getSqrtPriceAtTick_throwsForInt24Min() public {
+        vm.expectRevert(TickMath.InvalidTick.selector);
+        tickMath.getSqrtPriceAtTick(type(int24).min);
+    }
+
     function test_getSqrtPriceAtTick_throwsForTooLow() public {
         vm.expectRevert(TickMath.InvalidTick.selector);
         tickMath.getSqrtPriceAtTick(MIN_TICK - 1);