Jank now has its own custom IR

Jank has introduced a new custom intermediate representation (IR) designed specifically for its Clojure-based language, aiming to improve optimization and performance. This development is significant as it marks a shift from relying solely on LLVM IR, allowing for more semantic-aware transformations tailored to Jank’s unique features.

The developer behind Jank announced the creation of a high-level IR that operates at the semantic level of Clojure, unlike traditional low-level IRs like LLVM IR. This IR is stored as C++ data structures but can be rendered into Clojure data for debugging. It is designed to facilitate optimizations that leverage Clojure’s dynamic features, such as vars, transients, and lazy sequences. The IR is SSA-based and structured as a control flow graph, enabling more effective optimization passes tailored to Jank’s semantics.

Initially, Jank relied on LLVM IR for optimization, which was limited by LLVM’s low-level nature. The new IR aims to address this by providing a higher-level abstraction, potentially leading to better runtime performance and more efficient compiled code. The IR is currently in development, and the creator has provided a reference guide, but it is not yet considered stable or ready for production.

Why It Matters

This development matters because it could significantly enhance Jank’s ability to optimize code, making it more competitive with JVM-based environments like Clojure on the JVM. A custom IR tailored to Jank’s semantics allows for more targeted and effective optimizations, potentially leading to faster, more efficient programs.

For the broader Clojure community and language implementers, this represents an innovative approach to compiler design, emphasizing semantic-level optimizations rather than relying solely on low-level IRs. If successful, it could inspire similar strategies in other language projects.

Background

Historically, Jank has not been an optimizing compiler itself but delegated optimization tasks to LLVM IR, which is low-level and not aware of Clojure’s semantics. Over the past two months, the developer has been working on a new IR that operates at a higher level, specifically designed for Jank’s features. This move aligns with ongoing efforts to improve Jank’s performance and efficiency as a standalone compiler.

“I wanted an IR which operated at the level of Clojure’s semantics. This would be much higher level than LLVM IR and even much higher level than JVM’s bytecode.”

— Jank’s developer

“This IR is designed to make writing certain optimizations easier, such as single static assignment (SSA) form, and to better leverage Clojure’s polymorphism and indirection.”

— Jank’s developer

What Remains Unclear

It is not yet clear when the new IR will be production-ready or how much performance improvement it will deliver in practice. The stability and compatibility of the IR are still under development, and testing is ongoing.

What’s Next

Next steps include refining the IR, conducting performance benchmarks, and integrating it into Jank’s compiler pipeline. The developer plans to release more detailed documentation and potentially experimental builds for community testing.

Key Questions

What is an intermediate representation (IR)?

An IR is a simplified, abstract version of a program used by compilers to perform optimizations and transformations before generating machine code. It allows for more effective analysis and optimization at a higher level than raw machine instructions.

Why did Jank create its own IR instead of using LLVM IR?

LLVM IR is low-level and does not understand Clojure’s semantics, such as vars, transients, or lazy sequences. Jank’s custom IR operates at a higher level, enabling more semantic-aware optimizations tailored specifically to its language features.

How will the new IR impact Jank’s performance?

While specific performance gains are still being evaluated, the goal is to enable more effective optimizations, which could lead to faster runtime performance and more efficient compiled code.

Is this IR ready for production use?

No, the IR is still in development, and its stability, performance, and compatibility are not yet guaranteed. It is primarily a research and development effort at this stage.

What are the benefits of a high-level IR for a language like Jank?

A high-level IR allows the compiler to better understand the semantics of the language, enabling more targeted optimizations, reducing runtime overhead, and potentially simplifying the compilation process.