JSIR: A High-Level IR for JavaScript (discourse.llvm.org)

The LLVM MLIR community proposal describes JSIR, a high-level intermediate representation for JavaScript that preserves AST information to enable lossless round-trips between source, AST, and JSIR. Using MLIR regions for control flow and built-in dataflow analysis support, JSIR is presented as a foundation for source-to-source transformations such as decompilation, deobfuscation, and other tooling, and reports that it is already used in production at Google. The RFC emphasizes a near 1-to-1 mapping from ESTree nodes to JSIR operations and discusses design choices like reversible lowering back to AST.