2 months ago
- After building the AST, the next step in Zig compiler is generating the Zig Intermediate Representation (ZIR) using the AstGen stage.
- ZIR is an untyped intermediate representation, meaning types are not fully evaluated until later comptime analysis.
- ZIR consists of a sequence of instructions, each with a tag and data, often referencing other instructions or static values.
- AstGen introduces scope awareness, identifier resolution, and string interning, storing strings in a continuous array to free AST and source.
- ZIR instructions can embed static values, reference other instructions via index, or use tagged references for well-known primitives.
- Variable assignments in ZIR do not generate explicit instructions; instead, they are tracked via scopes that reference the value's instruction index.
- AstGen is run once per file, converting the entire AST into ZIR eagerly, and is the first stage to perform semantic validation like identifier checks.