JSIR: A High-Level IR for JavaScript

4 hours ago

JSIR is a high-level intermediate representation (IR) for JavaScript, developed at Google, that preserves all AST information and supports lossless round-trip conversions between source code, AST, and JSIR.
It leverages MLIR regions for control flow representation and provides dataflow analysis capabilities, addressing the lack of IR-based tools in the JavaScript community which traditionally rely on ASTs.
Key use cases include decompilation from Hermes bytecode to JavaScript, deobfuscation using source-to-source transformations, and integration with tools like Babel and SWC for parsing.
Design goals include a public, stable IR definition that closely mirrors ESTree, capturing all source-level information to enable high-fidelity source-to-source transformations.
JSIR distinguishes between l-values and r-values explicitly in the IR, uses region-based control flow structures (e.g., if, while statements), and offers an improved dataflow analysis API over MLIR's built-in framework.
Potential future steps involve adopting more MLIR built-in functionalities, contributing region-based dataflow analysis improvements upstream, and addressing dependencies for possible integration into the MLIR codebase.

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