Jank now has its own custom IR

Jank has unveiled a new custom intermediate representation (IR) designed specifically for its Clojure-based language, marking a significant step toward optimizing its compiler and runtime performance. This development aims to enable more advanced optimizations by working at a higher level of abstraction than traditional IRs like LLVM or JVM bytecode, tailored to Jank’s unique features and semantics.

The new IR is a high-level, SSA-based control flow graph representation, stored in memory as C++ data structures but renderable in Clojure for debugging. Unlike LLVM IR, which operates at a low level and lacks awareness of Clojure’s features such as vars, transients, and lazy sequences, Jank’s IR is designed to reflect the language’s semantics directly. The IR includes lifted vars and constants, and its structure supports optimizations that are more meaningful for Clojure code.

The developer behind Jank, who announced the IR, explained that previous reliance on LLVM IR limited optimization opportunities because LLVM’s low-level nature does not capture Clojure’s dynamism. The new IR aims to facilitate more effective optimizations, potentially improving runtime performance and compilation efficiency. The IR is currently in a developmental stage, with no guarantees on its stability or long-term API.

Why It Matters

This development is significant because it represents a shift toward language-specific compiler optimization, which could lead to faster, more efficient code execution for Jank programs. By designing an IR that aligns closely with Clojure’s semantics, Jank could surpass existing JVM-based tools in performance and flexibility, especially for dynamic and functional features. For users and developers, this could translate into a more powerful, performant environment for Clojure development on Jank.

Background

Historically, Jank relied on LLVM IR for optimization, which is low-level and language-agnostic, limiting the ability to optimize Clojure-specific features. The move to a custom IR reflects ongoing efforts to improve compiler performance and leverage the language’s unique characteristics. This is part of a broader trend in compiler design, where language-specific IRs are used to unlock more optimization opportunities, as seen in other projects like the JVM and GCC.

“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 developer

“This IR allows us to work directly with Clojure’s semantics, which should unlock more powerful optimizations and improve overall performance.”

— Jank developer

What Remains Unclear

It is not yet clear how stable or mature the IR will become, as it is still in early development and experimental. The long-term API and compatibility with existing tools remain uncertain. Additionally, the actual performance gains and real-world impact are still to be demonstrated through testing and benchmarking.

What’s Next

The next steps include refining the IR, developing optimization passes, and benchmarking its performance against previous compiler versions. The developer plans to release more details and potentially integrate the IR into the main build of Jank, with ongoing feedback from the community to improve stability and effectiveness.

Key Questions

What is an intermediate representation (IR)?

An IR is a more abstract set of instructions used by compilers to optimize and translate code before generating machine code. It allows for language-specific optimizations and portability across architectures.

Why did Jank create its own IR?

Jank’s previous reliance on LLVM IR limited optimization opportunities because LLVM IR is low-level and language-agnostic. A custom IR designed for Clojure’s semantics enables more targeted and effective optimizations.

How might this IR improve Jank’s performance?

By working at a higher level of abstraction that reflects Clojure’s features, the IR can facilitate optimizations that directly enhance runtime efficiency and compilation speed.

Is this IR stable and ready for production use?

No, the IR is still in early development and experimental. Its stability, API, and performance benefits are still being evaluated.