'irdl' Dialect

IR Definition Language Dialect IRDL is an SSA-based declarative representation of dynamic dialects. It allows the definition of dialects, operations, attributes, and types, with a declarative description of their verifiers. IRDL code is meant to be generated and not written by hand. As such, the design focuses on ease of generation/analysis instead of ease of writing/reading.

Users can define a new dialect with irdl.dialect, operations with irdl.operation, types with irdl.type, and attributes with irdl.attribute.

An example dialect is shown below:

irdl.dialect @cmath {
  irdl.type @complex {
    %0 = irdl.is_type : f32
    %1 = irdl.is_type : f64
    %2 = irdl.any_of(%0, %1)
    irdl.parameters(%2)
  }

  irdl.operation @mul {
    %0 = irdl.is_type : f32
    %1 = irdl.is_type : f64
    %2 = irdl.any_of(%0, %1)
    %3 = irdl.parametric_type : "cmath.complex"<%2>
    irdl.operands(%3, %3)
    irdl.results(%3)
  }
}

This program defines a cmath dialect that defines a complex type, and a mul operation. Both express constraints over their parameters using SSA constraint operations. Informally, one can see those SSA values as constraint variables that evaluate to a single type at constraint evaluation. For example, the result of the irdl.any_of stored in %2 in the mul operation will collapse into either f32 or f64 for the entirety of this instance of mul constraint evaluation. As such, both operands and the result of mul must be of equal type (and not just satisfy the same constraint).

IRDL variables are handle over mlir::Attribute. In order to support manipulating mlir::Type, IRDL wraps all types in an mlir::TypeAttr attribute. The rationale of this is to simplify the dialect.