⚡️ MerkleProof Verify Optimization (#240)

transmissions11 · May 18, 2022 · f878f20 · f878f20
1 parent deb69bd
commit f878f20
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Showing 2 changed files with 17 additions and 20 deletions.
diff --git a/.gas-snapshot b/.gas-snapshot
@@ -101,7 +101,7 @@ ERC20Test:testApprove() (gas: 31080)
 ERC20Test:testBurn() (gas: 57014)
 ERC20Test:testFailPermitBadDeadline() (gas: 36924)
 ERC20Test:testFailPermitBadNonce() (gas: 36874)
-ERC20Test:testFailPermitPastDeadline() (gas: 10938)
+ERC20Test:testFailPermitPastDeadline() (gas: 8589)
 ERC20Test:testFailPermitReplay() (gas: 66285)
 ERC20Test:testFailTransferFromInsufficientAllowance() (gas: 80837)
 ERC20Test:testFailTransferFromInsufficientBalance() (gas: 81336)
@@ -188,10 +188,10 @@ FixedPointMathLibTest:testMulWadUp() (gas: 1003)
 FixedPointMathLibTest:testMulWadUpEdgeCases() (gas: 981)
 FixedPointMathLibTest:testRPow() (gas: 2142)
 FixedPointMathLibTest:testSqrt() (gas: 2156)
-MerkleProofTest:testValidProofSupplied() (gas: 991)
-MerkleProofTest:testVerifyEmptyMerkleProofSuppliedLeafAndRootDifferent() (gas: 392)
-MerkleProofTest:testVerifyEmptyMerkleProofSuppliedLeafAndRootSame() (gas: 389)
-MerkleProofTest:testVerifyInvalidProofSupplied() (gas: 977)
+MerkleProofTest:testValidProofSupplied() (gas: 945)
+MerkleProofTest:testVerifyEmptyMerkleProofSuppliedLeafAndRootDifferent() (gas: 390)
+MerkleProofTest:testVerifyEmptyMerkleProofSuppliedLeafAndRootSame() (gas: 387)
+MerkleProofTest:testVerifyInvalidProofSupplied() (gas: 931)
 MultiRolesAuthorityTest:testCanCallPublicCapability() (gas: 34293)
 MultiRolesAuthorityTest:testCanCallWithAuthorizedRole() (gas: 80575)
 MultiRolesAuthorityTest:testCanCallWithCustomAuthority() (gas: 422681)

diff --git a/src/utils/MerkleProof.sol b/src/utils/MerkleProof.sol
@@ -18,26 +18,23 @@ library MerkleProof {
 
             // Iterate over proof elements to compute root hash.
             for {
-                let end := add(data, mul(mload(proof), 0x20))
+                // Left shift by 5 is equivalent to multiplying by 0x20.
+                let end := add(data, shl(5, mload(proof))) 
             } lt(data, end) {
                 data := add(data, 0x20)
             } {
                 let loadedData := mload(data)
-                switch gt(computedHash, loadedData)
-                case 0 {
-                    // Store elements to hash contiguously in scratch space.
-                    // Scratch space is 64 bytes (0x00 - 0x3f) and both elements are 32 bytes.
-                    mstore(0x00, computedHash)
-                    mstore(0x20, loadedData)
-                    computedHash := keccak256(0x00, 0x40)
-                }
-                default {
-                    mstore(0x00, loadedData)
-                    mstore(0x20, computedHash)
-                    computedHash := keccak256(0x00, 0x40)
-                }
+                // Slot of `computedHash` in scratch space.
+                // If the condition is true: 0x20, otherwise: 0x00.
+                let scratch := shl(5, gt(computedHash, loadedData))
+
+                // Store elements to hash contiguously in scratch space.
+                // Scratch space is 64 bytes (0x00 - 0x3f) and both elements are 32 bytes.
+                mstore(scratch, computedHash)
+                mstore(xor(scratch, 0x20), loadedData)
+                computedHash := keccak256(0x00, 0x40)
             }
             isValid := eq(computedHash, root)
         }
     }
-}
+}