fix Uniswap#752

src/PoolManager.sol

@@ -323,16 +323,13 @@ contract PoolManager is IPoolManager, ProtocolFees, NoDelegateCall, ERC6909Claim
     function _accountDelta(Currency currency, int128 delta, address target) internal {
         if (delta == 0) return;
 
-        int256 current = currency.getDelta(target);
-        int256 next = current + delta;
+        (int256 previous, int256 updated) = currency.applyDelta(target, delta);
 
-        if (next == 0) {
+        if (updated == 0) {
             NonZeroDeltaCount.decrement();
-        } else if (current == 0) {
+        } else if (previous == 0) {
             NonZeroDeltaCount.increment();
         }
-
-        currency.setDelta(target, next);
     }
 
     /// @notice Accounts the deltas of 2 currencies to a target address

src/libraries/CurrencyDelta.sol

@@ -15,21 +15,16 @@ library CurrencyDelta {
         }
     }
 
-    /// @notice sets a new currency delta for a given caller and currency
-    function setDelta(Currency currency, address caller, int256 delta) internal {
+    /// @notice applies a new currency delta for a given caller and currency
+    function applyDelta(Currency currency, address caller, int128 delta) internal returns (int256 previous, int256 next) {
         bytes32 hashSlot = _computeSlot(caller, currency);
 
         assembly {
-            tstore(hashSlot, delta)
+            previous := tload(hashSlot)
         }
-    }
-
-    /// @notice gets a new currency delta for a given caller and currency
-    function getDelta(Currency currency, address caller) internal view returns (int256 delta) {
-        bytes32 hashSlot = _computeSlot(caller, currency);
-
+        next = previous + delta;
         assembly {
-            delta := tload(hashSlot)
+            tstore(hashSlot, next)
         }
     }
 }