move cache into transient storage

.forge-snapshots/Quoter_exactInputSingle_oneForZero_multiplePositions.snap

@@ -1 +1 @@
-146153
+144148

.forge-snapshots/Quoter_exactInputSingle_zeroForOne_multiplePositions.snap

@@ -1 +1 @@
-151617
+149612

.forge-snapshots/Quoter_exactOutputSingle_oneForZero.snap

@@ -1 +1 @@
-80841
+78941

.forge-snapshots/Quoter_exactOutputSingle_zeroForOne.snap

@@ -1 +1 @@
-85635
+83735

.forge-snapshots/Quoter_quoteExactInput_oneHop_1TickLoaded.snap

@@ -1 +1 @@
-122679
+120674

.forge-snapshots/Quoter_quoteExactInput_oneHop_initializedAfter.snap

@@ -1 +1 @@
-147588
+145583

.forge-snapshots/Quoter_quoteExactInput_oneHop_startingInitialized.snap

@@ -1 +1 @@
-81611
+79606

.forge-snapshots/Quoter_quoteExactInput_twoHops.snap

@@ -1 +1 @@
-203446
+201436

.forge-snapshots/Quoter_quoteExactOutput_oneHop_1TickLoaded.snap

@@ -1 +1 @@
-142383
+120261

.forge-snapshots/Quoter_quoteExactOutput_oneHop_2TicksLoaded.snap

@@ -1 +1 @@
-172520
+150398

.forge-snapshots/Quoter_quoteExactOutput_oneHop_initializedAfter.snap

@@ -1 +1 @@
-142451
+120329

.forge-snapshots/Quoter_quoteExactOutput_oneHop_startingInitialized.snap

@@ -1 +1 @@
-119150
+97028

.forge-snapshots/Quoter_quoteExactOutput_twoHops.snap

@@ -1 +1 @@
-243720
+201476

src/base/BaseV4Quoter.sol

@@ -6,6 +6,7 @@ import {PoolKey} from "@uniswap/v4-core/src/types/PoolKey.sol";
 import {QuoterRevert} from "../libraries/QuoterRevert.sol";
 import {SqrtPriceLimitHelper} from "../libraries/SqrtPriceLimitHelper.sol";
 import {SafeCallback} from "../base/SafeCallback.sol";
+import {CacheAmountSpecified} from "../libraries/CacheAmountSpecified.sol";
 
 abstract contract BaseV4Quoter is SafeCallback {
     using SqrtPriceLimitHelper for uint160;
@@ -17,16 +18,25 @@ abstract contract BaseV4Quoter is SafeCallback {
 
     constructor(IPoolManager _poolManager) SafeCallback(_poolManager) {}
 
-    /// @dev cache used to check a safety condition in exact output swaps.
-    uint128 internal amountOutCached;
-
     /// @dev Only this address may call this function. Used to mimic internal functions, using an
     /// external call to catch and parse revert reasons
     modifier selfOnly() {
         if (msg.sender != address(this)) revert NotSelf();
         _;
     }
 
+    function _clearAmountSpecified() internal {
+        CacheAmountSpecified.set(0);
+    }
+
+    function _setAmountSpecified(uint256 amountSpecified) internal {
+        CacheAmountSpecified.set(amountSpecified);
+    }
+
+    function _getAmountSpecified() internal returns (uint256 amountSpecified) {
+        return CacheAmountSpecified.get();
+    }
+
     function _unlockCallback(bytes calldata data) internal override returns (bytes memory) {
         // Call this contract with the data in question. Each quote path
         (bool success, bytes memory returnData) = address(this).call(data);
@@ -54,6 +64,7 @@ abstract contract BaseV4Quoter is SafeCallback {
             hookData
         );
         // only exactOut case
+        uint256 amountOutCached = _getAmountSpecified();
         if (amountOutCached != 0 && amountOutCached != uint128(zeroForOne ? swapDelta.amount1() : swapDelta.amount0()))
         {
             revert InsufficientAmountOut();

src/lens/Quoter.sol

@@ -52,7 +52,7 @@ contract Quoter is IQuoter, BaseV4Quoter {
         try poolManager.unlock(abi.encodeCall(this._quoteExactOutputSingle, (params))) {}
         catch (bytes memory reason) {
             gasEstimate = gasBefore - gasleft();
-            if (params.sqrtPriceLimitX96 == 0) delete amountOutCached;
+            if (params.sqrtPriceLimitX96 == 0) _clearAmountSpecified();
             amountIn = reason.parseReturnData();
         }
     }
@@ -118,14 +118,14 @@ contract Quoter is IQuoter, BaseV4Quoter {
 
         for (uint256 i = pathLength; i > 0; i--) {
             pathKey = params.path[i - 1];
-            amountOutCached = amountOut;
+            _setAmountSpecified(amountOut);
 
             (PoolKey memory poolKey, bool oneForZero) = pathKey.getPoolAndSwapDirection(outputCurrency);
 
             swapDelta = _swap(poolKey, !oneForZero, int256(uint256(amountOut)), 0, pathKey.hookData);
 
             // always clear because sqrtPriceLimitX96 is set to 0 always
-            delete amountOutCached;
+            _clearAmountSpecified();
 
             amountOut = oneForZero ? uint128(-swapDelta.amount1()) : uint128(-swapDelta.amount0());
 
@@ -138,7 +138,7 @@ contract Quoter is IQuoter, BaseV4Quoter {
     /// @dev external function called within the _unlockCallback, to simulate a single-hop exact output swap, then revert with the result
     function _quoteExactOutputSingle(QuoteExactSingleParams calldata params) external selfOnly returns (bytes memory) {
         // if no price limit has been specified, cache the output amount for comparison inside the _swap function
-        if (params.sqrtPriceLimitX96 == 0) amountOutCached = params.exactAmount;
+        if (params.sqrtPriceLimitX96 == 0) _setAmountSpecified(params.exactAmount);
 
         BalanceDelta swapDelta = _swap(
             params.poolKey,
@@ -148,7 +148,7 @@ contract Quoter is IQuoter, BaseV4Quoter {
             params.hookData
         );
 
-        if (amountOutCached != 0) delete amountOutCached;
+        _clearAmountSpecified();
 
         // the input delta of a swap is negative so we must flip it
         uint256 amountIn = params.zeroForOne ? uint128(-swapDelta.amount0()) : uint128(-swapDelta.amount1());

src/libraries/CacheAmountSpecified.sol

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.24;
+
+/// @notice This is a temporary library that allows us to use transient storage (tstore/tload)
+/// TODO: This library can be deleted when we have the transient keyword support in solidity.
+library CacheAmountSpecified {
+    // bytes32(uint256(keccak256("AmountSpecified")) - 1)
+    bytes32 internal constant AMOUNT_SPECIFIED_SLOT = 0x040affe16a79096ebfed488ed052568637be7285d797c191b3a85e60cf8292f3;
+
+    function set(uint256 amountSpecified) internal {
+        assembly ("memory-safe") {
+            tstore(AMOUNT_SPECIFIED_SLOT, amountSpecified)
+        }
+    }
+
+    function get() internal view returns (uint256 amountSpecified) {
+        assembly ("memory-safe") {
+            amountSpecified := tload(AMOUNT_SPECIFIED_SLOT)
+        }
+    }
+}