Intermediate Representation (IR)

This crate contains the intermediate representation for AirScript, AirIR.

The purpose of the AirIR is to provide a simple and accurate representation of an AIR that allows for optimization and translation to constraint evaluator code in a variety of target languages.

Generating the AirIR

Generate an AirIR from either an AirScript AST (the output of the AirScript parser) or a MIR (the Middle Intermediate Representation for AirScript).

Example usage:

// parse the source string to a Result containing the AST or an Error
let ast = parse(source.as_str()).expect("Parsing failed");

// Create the compilation pipeline needed to translate the AST to AIR
let pipeline_with_mir = air_parser::transforms::ConstantPropagation::new(&diagnostics)
  .chain(mir::passes::AstToMir::new(&diagnostics))
  .chain(mir::passes::Inlining::new(&diagnostics))
  .chain(mir::passes::Unrolling::new(&diagnostics))
  .chain(air_ir::passes::MirToAir::new(&diagnostics))
  .chain(air_ir::passes::BusOpExpand::new(&diagnostics));

let pipeline_without_mir = air_parser::transforms::ConstantPropagation::new(&diagnostics)
  .chain(air_parser::transforms::Inlining::new(&diagnostics))
  .chain(air_ir::passes::AstToAir::new(&diagnostics));
  
// process the AST to get a Result containing the AIR or a CompileError
let air_from_ast = pipeline_without_mir.run(ast)
let air_from_mir = pipeline_with_mir.run(ast)

AirIR

Although generation of an AirIR uses a symbol table while processing the source AST, the internal representation only consists of the following:

• Name of the AIR definition represented by the AirIR.
• Segment Widths, represented by a vector that contains the width of each trace segment (currently main and auxiliary).
• Constants, represented by a vector that maps an identifier to a constant value.
• Public inputs, represented by a vector that maps an identifier to a size for each public input that was declared. (Currently, public inputs can only be declared as fixed-size arrays.)
• Periodic columns, represented by an ordered vector that contains each periodic column's repeating pattern (as a vector).
• Constraints, represented by the combination of:
  • a directed acyclic graph (DAG) without duplicate nodes.
  • a vector of ConstraintRoot for each trace segment (e.g. main or auxiliary), where ConstraintRoot contains the node index in the graph where each of the constraint starts and the constraint domain which specifies the row(s) accessed by each of the constraints.
  • contains both boundary and integrity constraints.