Modify ReentrancyGuard to reduce contract size (#3515)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Francisco <frangio.1@gmail.com>

CHANGELOG.md

@@ -9,6 +9,7 @@
  * `ERC20`: optimize `_transfer`, `_mint` and `_burn` by using `unchecked` arithmetic when possible. ([#3513](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3513))
  * `ERC721`: optimize transfers by making approval clearing implicit instead of emitting an event. ([#3481](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3481))
  * `ERC721`: optimize burn by making approval clearing implicit instead of emitting an event. ([#3538](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3538))
+ * `ReentrancyGuard`: Reduce code size impact of the modifier by using internal functions. ([#3515](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3515))
 
 ### Compatibility Note
 

contracts/security/ReentrancyGuard.sol

@@ -48,14 +48,20 @@ abstract contract ReentrancyGuard {
      * `private` function that does the actual work.
      */
     modifier nonReentrant() {
+        _nonReentrantBefore();
+        _;
+        _nonReentrantAfter();
+    }
+
+    function _nonReentrantBefore() private {
         // On the first call to nonReentrant, _notEntered will be true
         require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
 
         // Any calls to nonReentrant after this point will fail
         _status = _ENTERED;
+    }
 
-        _;
-
+    function _nonReentrantAfter() private {
         // By storing the original value once again, a refund is triggered (see
         // https://eips.ethereum.org/EIPS/eip-2200)
         _status = _NOT_ENTERED;