Vision

While developing a zkVM for an EVM-compatible, Wasm based rollup on Ethereum, Fluent explored methods to optimize the proving process of smart contracts. A major challenge lies in the fact that using a zkVM to support multiple VMs only allows for the proof of the root STF, while the remaining nested execution of other VMs requires emulation.

To address this issue, Fluent proposes a VM capable of performing nested execution without incurring additional emulation overhead. This is achieved through a hardware acceleration process similar to the translation of smart contracts, applications, and precompiled contracts into a specialized low-level intermediary representation (IR) binary structure known as rWasm. This structure can be proven much more efficient compared to running emulator software.

With its unique interruption system, rWasm emerged as an innovative solution for handling nested calls and compiling diverse smart contracts, revolutionizing the landscape of efficient zk-Wasm based applications on Ethereum.

Meet Blended Execution

With blended execution on Fluent, developers can create applications using languages and tools from various VMs yet coexisting in the same execution space. This is possible because all smart contracts share the same execution environment. As a result, native composability is achieved for anything within Fluent that can be represented as rWasm (which relies on Wasm and LLVM, making 17+ languages available for development).

Different VMs can be supported using an AOT translation process (efficient but time-consuming) or an emulation process ( very fast integration but with additional overhead). Fluent can enable execution environments like the EVM, bringing Solidity and Vyper support. Similarly, the new language Sway from Fuel can be integrated by running an FVM execution precompile. Entire EEs can be seamlessly integrated and accommodated in various modes, offering either Isolated EE (complete compatibility with the original EE where interoperability is achieved using deposit/withdrawal process) or Blended EE ( improved native composability with other VMs on Fluent).

Both users and developers obtain major benefits from blended execution because it enhances the experience of developers who are ready to expand the Fluent ecosystem by bringing more development languages and execution environments on board.

Product Vision

The Fluent Blended Execution Layer will revolutionize the way developers create, deploy, and prove smart contracts by unifying multiple VMs into a single, highly efficient execution environment. At the heart of this vision is rWasm, a unique IR language designed to bridge the gap between various VMs and EEs such as the EVM, SVM, and Wasm. By eliminating the emulation overhead typically associated with nested execution, Fluent enables faster, more secure, and more scalable smart contract execution.

Key features:

1. Unified Execution Environment: Support for multiple VMs and EEs through a single execution environment, enabling native composability between different smart contracts, tools, and languages.
2. rWasm Integration: Full compatibility with standard Wasm and support for over 17+ traditional programming languages, allowing developers to use familiar tools such as Rust, C, Solidity, TinyGo, and AssemblyScript without sacrificing performance.
3. Optimized Proving Infrastructure: Efficient proving through rWasm that drastically reduces overhead and complexity, providing optimal performance for ZK circuits.
4. Seamless Expansion: Advanced AOT compilers to integrate new VMs and EEs, ensuring extensibility for future-proofing and scalability.
5. Security and Extensibility: BlendedVM unifies the execution space, providing enhanced security and preventing vulnerabilities that arise from managing multiple VMs while enabling new VMs to be added in trusted or trustless modes.

The Fluent Blended Execution Layer empowers developers to build diverse applications without managing disparate systems, optimizing their experience and fostering rapid growth in the Ethereum ecosystem.

Technical Vision

Extracting traces is crucial for proving. It involves obtaining snapshots of stack and memory operations to feed into zk circuits. Aligning the IR language with the trace structure and ensuring its compatibility with zk is essential to minimize circuit size, ultimately improving proving speed and reducing code complexity. rWasm, as an IR binary language, combines execution concepts and maps its execution trace to the zkVM circuit structure. This approach aims to achieve optimal performance, minimizing both proving and execution overhead.

Blended execution natively supports multiple VMs and EEs within a single execution environment, and within Fluent, is enabled by employing a single IR known as rWasm, which serves as its primary VM. This IR enables the verification of all state transitions occurring within the system, encompassing various VMs and EEs. In the case of the Fluent L2, the EVM, SVM, and Wasm are supported. As a result, developers familiar with any of these primitives can leverage circuits designed for rWasm and effortlessly obtain the necessary optimal proving infrastructure for their applications. In essence, blended execution acts as a state verification function responsible for representing every operation within the Fluent execution layer.

Given that rWasm serves as the IR language for Fluent, it has the potential to represent not only Wasm or EVM but also other VMs and EEs. This is facilitated by providing dedicated AOT compilers for these platforms or in some cases utilizing emulation software.

rWasm is a derivative of the Wasm assembly language that keeps 100% backward compatibility with original Wasm standards. Leveraging the extensive adoption and support of Wasm, rWasm enables blockchain developers to effortlessly create new applications in traditional languages like Rust and C. Fluent's advanced AOT compilers handle all IR compilation tasks, simplifying the development and deployment process of Wasm-based blockchain applications in the Ethereum ecosystem.