JSIR: LLVM Community Proposes High-Level Intermediate Representation for JavaScript

JSIR: Bringing JavaScript into the LLVM Compiler Infrastructure

The LLVM community is considering a proposal for JSIR (JavaScript Intermediate Representation), a high-level IR for JavaScript built on MLIR that would bring JS compilation into the LLVM ecosystem.

What This Means

Currently, JavaScript compilation happens in separate compiler pipelines (V8's TurboFan, SpiderMonkey's Warp, JavaScriptCore's DFG/FTL). JSIR would create a shared, high-level IR within LLVM's MLIR framework, potentially enabling:

• Cross-engine optimization — Research and optimizations applicable across JS engines
• Better Wasm interop — Unified compilation for JS and WebAssembly
• New JIT possibilities — Leverage LLVM's mature optimization passes
• Language research — Easier experimentation with JS language extensions

Why It Matters

• HN 43 points and growing — Significant community interest
• LLVM adoption — If accepted, JSIR would bring JavaScript into the most widely-used compiler infrastructure
• Industry impact — Could eventually influence how all major browsers compile JavaScript
• MLIR-based — Builds on the modern, extensible MLIR framework rather than legacy LLVM IR