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Edit rustc_middle::dep_graph module documentation

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Co-authored-by: Joshua Nelson <joshua@yottadb.com>
Co-authored-by: Camelid <camelidcamel@gmail.com>
This commit is contained in:
pierwill 2021-01-17 11:16:17 -08:00
parent edeb631ad0
commit b29353af09
1 changed files with 10 additions and 7 deletions
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17
compiler/rustc_middle/src/dep_graph/dep_node.rs
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@ -1,16 +1,17 @@
//! This module defines the `DepNode` type which the compiler uses to represent
//! nodes in the dependency graph.
//! Nodes in the dependency graph.
//!
//! A `DepNode` consists of a `DepKind` (which
//! specifies the kind of thing it represents, like a piece of HIR, MIR, etc)
//! and a `Fingerprint`, a 128-bit hash value the exact meaning of which
//! A node in the [dependency graph] is represented by a [`DepNode`].
//! A `DepNode` consists of a [`DepKind`] (which
//! specifies the kind of thing it represents, like a piece of HIR, MIR, etc.)
//! and a [`Fingerprint`], a 128-bit hash value, the exact meaning of which
//! depends on the node's `DepKind`. Together, the kind and the fingerprint
//! fully identify a dependency node, even across multiple compilation sessions.
//! In other words, the value of the fingerprint does not depend on anything
//! that is specific to a given compilation session, like an unpredictable
//! interning key (e.g., NodeId, DefId, Symbol) or the numeric value of a
//! interning key (e.g., `NodeId`, `DefId`, `Symbol`) or the numeric value of a
//! pointer. The concept behind this could be compared to how git commit hashes
//! uniquely identify a given commit and has a few advantages:
//! uniquely identify a given commit. The fingerprinting approach has
//! a few advantages:
//!
//! * A `DepNode` can simply be serialized to disk and loaded in another session
//! without the need to do any "rebasing" (like we have to do for Spans and
@ -51,6 +52,8 @@
//! than a zeroed out fingerprint. More generally speaking, it relieves the
//! user of the `DepNode` API of having to know how to compute the expected
//! fingerprint for a given set of node parameters.
//!
//! [dependency graph]: https://rustc-dev-guide.rust-lang.org/query.html
use crate::ty::TyCtxt;