circt/docs/Dialects/Sim/RationaleSim.md

Simulation (Sim) Dialect Rationale

This document describes various design points of the sim dialect, why it is the way it is, and current status. This follows in the spirit of other MLIR Rationale docs.

Introduction

The sim dialect provides a high-level representation for simulator-specific operations. The purpose of the dialect is to provide a high-level representation for constructs which interact with simulators (Verilator, VCS, Arc, ...) that are easy to analyze and transform in the compiler.

Operations

Plusargs

The sim.plusarg_test and sim.plusarg_value operations are wrappers around the SystemVerilog built-ins which access command-line arguments. They are cleaner from a data-flow perspective, as they package the wires and if-statements involved into compact operations that can be trivially handled by analyses.