Gas optimization on erc-20 (#182)

* added profiler

* gas optimization

* updated comment

* Update contracts/UFragments.sol

Co-authored-by: Brandon Iles <[email protected]>

Co-authored-by: Brandon Iles <[email protected]>

Author: aalavandhan

README.md

@@ -61,6 +61,9 @@ yarn format
 
 # Run solidity coverage report (compatible with node v12)
 yarn coverage
+
+# Run solidity gas usage report
+yarn profile
 ```
 
 ## License

contracts/UFragments.sol

@@ -94,36 +94,40 @@ contract UFragments is ERC20Detailed, Ownable {
         onlyMonetaryPolicy
         returns (uint256)
     {
+        uint256 oldTotalSupply = _totalSupply;
         if (supplyDelta == 0) {
-            emit LogRebase(epoch, _totalSupply);
-            return _totalSupply;
+            emit LogRebase(epoch, oldTotalSupply);
+            return oldTotalSupply;
         }
 
+        uint256 newTotalSupply;
         if (supplyDelta < 0) {
-            _totalSupply = _totalSupply.sub(uint256(supplyDelta.abs()));
+            newTotalSupply = oldTotalSupply.sub(uint256(supplyDelta.abs()));
         } else {
-            _totalSupply = _totalSupply.add(uint256(supplyDelta));
+            newTotalSupply = oldTotalSupply.add(uint256(supplyDelta));
         }
 
-        if (_totalSupply > MAX_SUPPLY) {
-            _totalSupply = MAX_SUPPLY;
+        if (newTotalSupply > MAX_SUPPLY) {
+            newTotalSupply = MAX_SUPPLY;
         }
 
-        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);
+        _gonsPerFragment = TOTAL_GONS.div(newTotalSupply);
 
         // From this point forward, _gonsPerFragment is taken as the source of truth.
-        // We recalculate a new _totalSupply to be in agreement with the _gonsPerFragment
+        // We recalculate a newTotalSupply to be in agreement with the _gonsPerFragment
         // conversion rate.
         // This means our applied supplyDelta can deviate from the requested supplyDelta,
         // but this deviation is guaranteed to be < (_totalSupply^2)/(TOTAL_GONS - _totalSupply).
         //
         // In the case of _totalSupply <= MAX_UINT128 (our current supply cap), this
         // deviation is guaranteed to be < 1, so we can omit this step. If the supply cap is
         // ever increased, it must be re-included.
-        // _totalSupply = TOTAL_GONS.div(_gonsPerFragment)
+        // newTotalSupply = TOTAL_GONS.div(_gonsPerFragment)
 
-        emit LogRebase(epoch, _totalSupply);
-        return _totalSupply;
+        _totalSupply = newTotalSupply;
+
+        emit LogRebase(epoch, newTotalSupply);
+        return newTotalSupply;
     }
 
     function initialize(address owner_) public initializer {
@@ -247,10 +251,11 @@ contract UFragments is ERC20Detailed, Ownable {
      * @param addedValue The amount of tokens to increase the allowance by.
      */
     function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
-        _allowedFragments[msg.sender][spender] = _allowedFragments[msg.sender][spender].add(
-            addedValue
-        );
-        emit Approval(msg.sender, spender, _allowedFragments[msg.sender][spender]);
+        uint256 oldValue = _allowedFragments[msg.sender][spender];
+        uint256 newValue = oldValue.add(addedValue);
+
+        _allowedFragments[msg.sender][spender] = newValue;
+        emit Approval(msg.sender, spender, newValue);
         return true;
     }
 
@@ -262,12 +267,15 @@ contract UFragments is ERC20Detailed, Ownable {
      */
     function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
         uint256 oldValue = _allowedFragments[msg.sender][spender];
+        uint256 newValue;
         if (subtractedValue >= oldValue) {
-            _allowedFragments[msg.sender][spender] = 0;
+            newValue = 0;
         } else {
-            _allowedFragments[msg.sender][spender] = oldValue.sub(subtractedValue);
+            newValue = oldValue.sub(subtractedValue);
         }
-        emit Approval(msg.sender, spender, _allowedFragments[msg.sender][spender]);
+
+        _allowedFragments[msg.sender][spender] = newValue;
+        emit Approval(msg.sender, spender, newValue);
         return true;
     }
 }

hardhat.config.ts

@@ -4,6 +4,7 @@ import '@nomiclabs/hardhat-ethers'
 import '@nomiclabs/hardhat-waffle'
 import '@openzeppelin/hardhat-upgrades'
 import 'solidity-coverage'
+import 'hardhat-gas-reporter'
 
 require('./scripts/deploy')
 
@@ -14,4 +15,9 @@ export default {
   mocha: {
     timeout: 100000,
   },
+  gasReporter: {
+    currency: 'USD',
+    enabled: process.env.REPORT_GAS ? true : false,
+    excludeContracts: ['mocks/'],
+  },
 } as HardhatUserConfig

package.json

@@ -20,6 +20,7 @@
   "scripts": {
     "compile": "yarn hardhat compile",
     "test": "yarn hardhat test",
+    "profile": "REPORT_GAS=true yarn hardhat test test/unit/*.ts",
     "coverage": "yarn hardhat coverage --testfiles 'test/unit/*.ts'",
     "format": "yarn prettier --config .prettierrc --write '**/*.ts' 'contracts/**/*.sol'",
     "lint": "yarn solhint 'contracts/**/*.sol'"
@@ -52,6 +53,7 @@
     "typescript": "^4.0.2"
   },
   "dependencies": {
+    "hardhat-gas-reporter": "^1.0.4",
     "openzeppelin-eth": "2.0.2-standalone"
   }
 }