syrup_backend

This is a prototype implementation of the backend of the syrup tool chain presented in

"Synthesis of Super-Optimized Smart Contracts using Max-SMT", CAV 2020, Elvira Albert, Pablo Gordillo, Albert Rubio, and Maria A Schett

The tool takes as input a Stack Functional Specification (SFS) describing the source and target stack of the Ethereum Virtual Machine (EVM) and, if successful, produces synthesized and optimized EVM bytecode to transform the source into the target stack by encoding the problem into Max-SMT.

Examples

In examples/add/input.json is the SFS for

• source_stack: [x_0, x_1, x_2, x3]
• target_stack: [x_0 + x1, x2 + x3]

For this SFS syrup_backend produces the EVM bytecode:

ADD SWAP2 ADD SWAP1.

In the running example of CAV 2020 we take a block

PUSH 0 DUP1 PUSH 0 DUP6 DUP8 ADD SWAP2 POP DUP4 DUP6 ADD SWAP1 POP DUP1 DUP3 EXP SWAP3 POP POP POP SWAP5 SWAP4 POP POP POP POP.

from the Solidity file in examples/cav2020/running-example.sol compiled to the bytecode examples/cav2020/running-example.evm.

In examples/cav2020/input.json is the SFS generated from the bytecode with a current cost of 126. For this SFS syrup_backend produces the EVM bytecode reducing the cost to 72:

ADD SWAP2 ADD EXP SWAP1

Install & Run

The easiest way to install syrup_backend is using opam. Simply run opam install . after cloning the repository. Then syrup-backend -help will provide help.

Max-SMT solvers supported by syrup_backend are

• Z3, version4.8.7
• Barcelogic
• OptiMathSat, version 1.6.3

For each of these solvers, syrup_backend can -write-only an SMT encoding. When given a -path to the executable of the respective solver, syrup_backend calls the solver directly.