tame/tamer/src/asg/mod.rs

81 lines
3.0 KiB
Rust
Raw Normal View History

// Abstract semantic graph (ASG) intermediate representation (IR)
//
// Copyright (C) 2014-2022 Ryan Specialty Group, LLC.
2020-03-06 11:05:18 -05:00
//
// This file is part of TAME.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//! Abstract semantic graph.
//!
//! The [abstract semantic graph][asg] (ASG) is an IR representing the
//! relationship between objects using a directed [graph][].
//! An _object_ is an identifier or expression.
//!
//! Since TAME is a declarative language,
//! the ASG does not represent control flow;
//! instead, it represents the relationship between objects and their
//! dependencies.
//! Control flow is determined solely by the [linker][crate::ld] based on
//! these dependencies.
//!
//! See [`crate::global`] for available index sizes depending on context.
//! For example,
//! a linker may choose to use [`crate::global::ProgIdentSize`];
//!
//!
//! Graph Structure
//! ===============
//! Each node (vector) in the graph represents an [`Object`],
//! such as an identifier or an expression.
//! Each directed edge `(A->B)` represents that `A` depends upon `B`.
//!
//! Graphs may contain cycles for recursive functions—that is,
//! TAME's ASG is _not_ a DAG.
//! Mutually recursive functions are therefore represented as
//! [strongly connected components][scc].
//!
//! [asg]: https://en.wikipedia.org/wiki/Abstract_semantic_graph
//! [graph]: https://en.wikipedia.org/wiki/Graph_(discrete_mathematics)
//! [scc]: https://en.wikipedia.org/wiki/Strongly_connected_component
//!
//! Each object may have a number of valid states;
//! see [`Ident`] for valid object states and transitions.
//!
//! Missing Identifiers
//! -------------------
//! Since identifiers in TAME can be defined in any order relative to their
//! dependencies within a source file,
//! it is often the case that a dependency will have to be added to the
//! graph before it is resolved.
//! For example,
//! [`Asg::add_dep_lookup`] will add an [`Ident::Missing`] to the graph
//! if either identifier has not yet been declared.
mod error;
mod graph;
mod ident;
mod object;
pub use error::AsgError;
pub use graph::{Asg, AsgResult, IndexType, ObjectRef};
pub use ident::{
FragmentText, Ident, IdentKind, Source, TransitionError, TransitionResult,
UnresolvedError,
};
pub use object::Object;
/// Default concrete ASG implementation.
pub type DefaultAsg = graph::Asg;