SLOAD-SSTORE pair special handling

[Scooletz]

WrappedEth that uses a regular ERC20. It can be seen decompiled under here and you can see its Etherscan profile. As it's ERC20 one of the core operations is the transfer that consists of two Read-Update-Write pairs, that access one StorageCell. Unfortunately, the underlying encoding of the key of the StorageCell index must take place twice. With IL-EVM we could optimize it by properly noticing SLOAD followed by SSTORE for the same value. It's worth to notice that Solidity/Yul will do their job here and the SHA3 that creates the index will be calculated only once.

PUSH1     0x20
ADD       
PUSH1     0x0
SHA3      
PUSH1     0x0
DUP3      
DUP3      
SLOAD
SUB     (or ADD if this is the transfer to)    
SWAP3     
POP       
POP       
SWAP1
SSTORE