StateVarPlusEqVsEqPlus.md

StateVarPlusEqVsEqPlus_p.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0; // optimize 200

/**
 * @title StateVarPlusEqVsEqPlus
 * @author IllIllI
 */
contract StateVarPlusEqVsEqPlus {
    uint256 varr = 1;

    function test() external returns (uint256) {
        varr += block.number;
        return varr;
    }
}

StateVarPlusEqVsEqPlus_e.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0; // optimize 200

/**
 * @title StateVarPlusEqVsEqPlus
 * @author IllIllI
 */
contract StateVarPlusEqVsEqPlus {
    uint256 varr = 1;

    function test() external returns (uint256) {
        varr = varr + block.number;
        return varr;
    }
}

Diff

diff --git a/StateVarPlusEqVsEqPlus_p.sol b/StateVarPlusEqVsEqPlus_e.sol
index 31775a1..623d154 100644
--- a/StateVarPlusEqVsEqPlus_p.sol
+++ b/StateVarPlusEqVsEqPlus_e.sol
@@ -9,7 +9,7 @@ contract StateVarPlusEqVsEqPlus {
     uint256 varr = 1;
 
     function test() external returns (uint256) {
-        varr += block.number;
+        varr = varr + block.number;
         return varr;
     }
 }

Compiled binary

$ solc StateVarPlusEqVsEqPlus_p.sol --bin --optimize --optimize-runs 200 | egrep "^60[0-9]+"
6080604052600160005534801561001557600080fd5b5060c7806100246000396000f3fe6080604052348015600f57600080fd5b506004361060285760003560e01c8063f8a8fd6d14602d575b600080fd5b60336047565b604051603e91906065565b60405180910390f35b60004360008082825460589190606e565b9091555050600054905090565b90815260200190565b60008219821115608c57634e487b7160e01b81526011600452602481fd5b50019056fea264697066735822122084f18c25ca3843d1f0f1ddf7bc90bef1163ea6a5ac7dba8b97f40fa3fd2ef83a64736f6c63430008000033

$ solc StateVarPlusEqVsEqPlus_e.sol --bin --optimize --optimize-runs 200 | egrep "^60[0-9]+"
6080604052600160005534801561001557600080fd5b5060c1806100246000396000f3fe6080604052348015600f57600080fd5b506004361060285760003560e01c8063f8a8fd6d14602d575b600080fd5b60336047565b604051603e9190605f565b60405180910390f35b600043600054605591906068565b6000819055905090565b90815260200190565b60008219821115608657634e487b7160e01b81526011600452602481fd5b50019056fea2646970667358221220aa5b50873df0045c32f138c5b8119fe52dbd818b3e305f88bbe93079ce8e4cd964736f6c63430008000033

Opcodes

PC.Pe	Operation.Pe	Gas.Pe	PC.Ep	Operation.Ep	Gas.Ep
110(0x6e)	NUMBER(0x43)	2	110(0x6e)	NUMBER(0x43)	2
111(0x6f)	PUSH1(0x60) ["0x00"]	3	111(0x6f)	PUSH1(0x60) ["0x00"]	3
113(0x71)	DUP1(0x80)	3
114(0x72)	DUP3(0x82)	3
115(0x73)	DUP3(0x82)	3
116(0x74)	SLOAD(0x54)	2100	113(0x71)	SLOAD(0x54)	2100
117(0x75)	PUSH1(0x60) ["0x58"]	3	114(0x72)	PUSH1(0x60) ["0x55"]	3
119(0x77)	SWAP2(0x91)	3	116(0x74)	SWAP2(0x91)	3
120(0x78)	SWAP1(0x90)	3	117(0x75)	SWAP1(0x90)	3
121(0x79)	PUSH1(0x60) ["0x6e"]	3	118(0x76)	PUSH1(0x60) ["0x68"]	3
123(0x7b)	JUMP(0x56)	8	120(0x78)	JUMP(0x56)	8
124(0x7c)	JUMPDEST(0x5b)@0x7c	1	121(0x79)	JUMPDEST(0x5b)@0x79	1
			122(0x7a)	PUSH1(0x60) ["0x00"]	3
			124(0x7c)	DUP2(0x81)	3
125(0x7d)	SWAP1(0x90)	3	125(0x7d)	SWAP1(0x90)	3
126(0x7e)	SWAP2(0x91)	3
127(0x7f)	SSTORE(0x55)	20000	126(0x7e)	SSTORE(0x55)	20000
128(0x80)	POP(0x50)	2
129(0x81)	POP(0x50)	2
130(0x82)	PUSH1(0x60) ["0x00"]	3
132(0x84)	SLOAD(0x54)	100
133(0x85)	SWAP1(0x90)	3	127(0x7f)	SWAP1(0x90)	3
134(0x86)	POP(0x50)	2	128(0x80)	POP(0x50)	2
135(0x87)	SWAP1(0x90)	3	129(0x81)	SWAP1(0x90)	3
136(0x88)	JUMP(0x56)	8	130(0x82)	JUMP(0x56)	8
	Total.Pe:	22264		Total.Ep:	22151

The change provides a savings of 113 gas