LLL to LLVM-IR compiler

LLL Smart-contract language to LLVM compiler prototype.

Created at SerialHack hackathon, Dec. 2018.

• Presentation PDF
• Demo video 1
• Demo video 2
• Youtube Live Stream

Problem to solve

The blockchain ecosystem needs reusable, standard, compatible and pluggable stack consisting of:

• high-level smart-contract languages;
• compilers;
• virtual machines, interpreters and emulators;
• different tools like code analyzers and test frameworks

In legacy world we already have ecosystem-wide standard of compilers and processors - LLVM.

Decentralised state engines running on top of blockchains/DAGs are very specific compared to hardware machines. And high-level languages for smart-contracts development have a lot of functional gaps compared to general-purpose langs. Solidity and EVM cannot be easy stretched to LLVM design.

Research. Why LLL, not Solidity

The Solidity compiler (solc) was initially designed without keeping LLVM in mind and seemed to lack intermediate representation (IR) in its internal design. Solc has a pretty complex Lexer, Parser and AST but unfortunately we found its internal mechanics too complex to build some minimal viable implementation within hackathon time constraints.

As a more primitive and achievable task we took the alternative language - Lower-Level Lisp-like smart-contract lang called LLL which is much simpler than Solidity then added LLVM-IR output to the compiler.

LLLc still produces EVM bytecode by default in no flag given. But invoked with -l option it builds LLVM-IR consumable by LLVM backends.

Results

We implemented LLL to LLVM-IR compiler supporting nested s-expressions with addition and subtraction math. The result code can be compiled to any LLVM backend including native execution by lli.

Install

LLVM toolset should be installed locally. If you using MacOS, install LLVM via homebrew and set LLVM_DIR env variable before installing solidity.

export LLVM_DIR=/usr/local/Cellar/llvm/7.0.0/lib/cmake

Official solidity guide

Run

In text editor create LLL contract source (only math operators and nesting supported)

(/ 10 (- 4 2))

Compile lll source to LLVM IR

lllc -l /path/to/lll/source.lll

Run LLVM IR code on CPU

lli /path/to/LLVM_IR/source.ll

Verify

Compile the same source to EVM bytecode (without -l flag)

lllc /path/to/lll/source.lll

Run bytecode (deploy the contract) to EVM wia web3 and retrieve the contract source by address.

The results should be equal.

Authors

• Kirill Varlamov, OnGrid Systems (github, site)
• Roman Nesytov, OnGrid Systems (github, site)