The Translatable Intermediate Representation (XIR)

XIR, packaged as Python package xlatir, is a restricted dialect of Python a la RPython. The primary purpose of XIR is to serve as a vehicle for specification of instruction set semantics that can be translated to other languages. Currently translations to C and SMT-LIB are supported.

XIR is still in heavy development, and in particular, bears vestiges of the time it was used to develop instruction set semantics for the PTX GPU virtual ISA. Eventually, XIR will become more general purpose.

To install:

  python3 setup.py develop --user

Note: this does not yet install the binaries into some bin directory accessible from the path.

Documentation

XIR is documented using MkDocs.

To view the documentation, install MkDocs, and then in the docs/xir directory, run mkdocs serve. The documentation will be available through your browser.

XIR dialects

There are several XIR dialects. All of them are syntactically compatible with Python3. However, some dialects of XIR support additional features like macros and templates which make them semantically incompatible with Python3. The tool xirconvert.py can convert programs written in these dialects to the plain XIR dialect which strives to be semantically compatible with Python3.

Libraries

Plain XIR does not support any Python operators beyond (AST) Call, Subscript, and Attribute (see xirsyntax.py for the definitive syntax definition).

Therefore, all operations such as addition, subtraction must be performed using function calls. Since XIR is typed, declarations for these functions are provided by a "standard library" (xirbuiltins.pyi) that accompanies XIR. For the most part, these declarations uses mypy-style type annotations. However, there are extensions (e.g. for constant-size array declarations) that are not recognized by mypy.

Additional functionality beyond standard operators can be added by defining ISA-specific libraries.

Currently the supported base types are hardcoded (see xlatir.xir.usrlib) and cannot be specified by the user, though mypy-style aliases are supported and strongly encouraged.

It is intended that the semantics for library functions be user-definable. Currently, this is not the case.

Examples

A simple definition: eBPF in XIR.

The PTX definition in XIR -- TODO.

Copyright

SPDX-FileCopyrightText: 2020,2021,2023 University of Rochester

SPDX-License-Identifier: MIT