Merge pull request #21 from ProjectOpenSea/0age-patch-1

Make ERC20 preapproval check branchless
ProjectOpenSea · Nov 29, 2023 · 057bb1f · 057bb1f
2 parents 38aad7a + e321e65
commit 057bb1f
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Showing 2 changed files with 9 additions and 10 deletions.
diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
@@ -2,3 +2,4 @@
 # Github Actions automatically updated formatting with forge fmt\n3b40d0f5cfd25b67a335ee2c8d7c9660d5bfd7f5
 # Github Actions automatically updated formatting with forge fmt\n2d96311b29055c5b9a0b632176ce3b8d78a23a89
 # Github Actions automatically updated formatting with forge fmt\ne2d336bbb0331c7716c16fed64f51be6c270ad02
+# Github Actions automatically updated formatting with forge fmt\n3458423c8716bdcd3875cde4597dcae377a16620
diff --git a/src/tokens/erc20/ERC20ConduitPreapproved_Solady.sol b/src/tokens/erc20/ERC20ConduitPreapproved_Solady.sol
@@ -61,16 +61,13 @@ abstract contract ERC20ConduitPreapproved_Solady is ERC20, IPreapprovalForAll {
             mstore(0x0c, or(from_, SOLADY_ERC20_ALLOWANCE_SLOT_SEED))
             let allowanceSlot := keccak256(0x0c, 0x34)
             let allowance_ := sload(allowanceSlot)
-            // If the caller is the conduit and allowance is 0, set to type(uint256).max. If the allowance is type(uint256).max, set to 0.
-            let isConduit := eq(caller(), CONDUIT)
-            if isConduit {
-                let conduitAllowance_ := allowance_
-                if eq(allowance_, 0) { conduitAllowance_ := not(0) }
-                if eq(allowance_, not(0)) { conduitAllowance_ := 0 }
-                if iszero(eq(allowance_, conduitAllowance_)) { allowance_ := conduitAllowance_ }
-            }
-            // If the allowance is not the maximum uint256 value.
-            if add(allowance_, 1) {
+
+            // "flip" allowance if caller is CONDUIT and if allowance_ is 0 or type(uint256).max.
+            allowance_ :=
+                xor(allowance_, mul(and(eq(caller(), CONDUIT), iszero(and(allowance_, not(allowance_)))), not(0)))
+
+            // If the allowance is not the maximum uint256 value:
+            if not(allowance_) {
                 // Revert if the amount to be transferred exceeds the allowance.
                 if gt(amount, allowance_) {
                     mstore(0x00, 0x13be252b) // `InsufficientAllowance()`.
@@ -79,6 +76,7 @@ abstract contract ERC20ConduitPreapproved_Solady is ERC20, IPreapprovalForAll {
                 // Subtract and store the updated allowance.
                 sstore(allowanceSlot, sub(allowance_, amount))
             }
+
             // Compute the balance slot and load its value.
             mstore(0x0c, or(from_, SOLADY_ERC20_BALANCE_SLOT_SEED))
             let fromBalanceSlot := keccak256(0x0c, 0x20)