[RFC] JSIR: A High-Level IR for JavaScript

This RFC introduces JSIR, a high-level IR for JavaScript: JSIR preserves all information from the AST and supports high-fidelity round-trip between source ↔ AST ↔ JSIR; JSIR uses MLIR regions to represent control flow structures; JSIR supports dataflow analysis. JSIR is developed and deployed in production at Google for code analysis and transform use cases. JSIR is open source here: GitHub - google/jsir: Next-generation JavaScript analysis tooling · GitHub. Motivation Industry trend of bui...