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//! The merged call graph.
//!
//! The driver emits one [`Artifact`] per crate. Merging them yields a single
//! graph in which every function has a dense index, which keeps the solver's
//! state in flat vectors.
use crate::{
model::{Artifact, Body, BuildConfig, CallSite, FuncKey, Reified},
util::Map,
};
/// A dense index into [`Graph`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct FuncId(pub u32);
impl FuncId {
/// The index as a `usize`, for slicing.
#[must_use]
pub const fn index(self) -> usize {
self.0 as usize
}
/// A dense index turned into an identifier.
///
/// A graph that large cannot be built in the first place, so clamping is
/// only here to keep the conversion total.
#[must_use]
pub fn from_index(index: usize) -> Self {
Self(u32::try_from(index).unwrap_or(u32::MAX))
}
}
/// A merged, indexed call graph.
#[derive(Debug)]
pub struct Graph {
bodies: Vec<Body>,
by_key: Map<FuncKey, FuncId>,
callers: Vec<Vec<FuncId>>,
config: Option<BuildConfig>,
}
impl Graph {
/// Merges per-crate artifacts into one graph.
///
/// A function may be observed more than once, because a generic body is
/// instantiated in every crate that uses it. The richest record wins: a
/// body with MIR always replaces an opaque placeholder.
#[must_use]
pub fn from_artifacts(artifacts: Vec<Artifact>) -> Self {
let mut graph = Self {
bodies: Vec::new(),
by_key: Map::default(),
callers: Vec::new(),
config: None,
};
let mut reified: Vec<Reified> = Vec::new();
for artifact in artifacts {
if graph.config.is_none() {
graph.config = Some(artifact.config.clone());
}
for body in artifact.bodies {
graph.insert_body(body);
}
reified.extend(artifact.reified);
}
graph.expand_fn_pointers(&reified);
graph.materialize_missing_callees();
graph.build_reverse_edges();
graph
}
/// Appends candidate edges for calls made through function pointers.
///
/// A reachable function reified to a pointer of the right signature is
/// what such a call could be. The edges are marked as candidates, so
/// following them stays the caller's choice, and the unresolved edge
/// stays alongside them either way.
fn expand_fn_pointers(&mut self, reified: &[Reified]) {
if reified.is_empty() {
return;
}
for body in &mut self.bodies {
let mut extra: Vec<CallSite> = Vec::new();
for call in &body.calls {
let Some(sig) = &call.sig else { continue };
for target in reified {
if &target.sig != sig {
continue;
}
let mut candidate = call.clone();
candidate.callee = Some(target.key.clone());
candidate.callee_display.clone_from(&target.display);
candidate.candidate = true;
candidate.sig = None;
extra.push(candidate);
}
}
body.calls.extend(extra);
}
}
/// Adds or upgrades one body.
fn insert_body(&mut self, body: Body) {
if let Some(&id) = self.by_key.get(&body.key) {
let existing = &mut self.bodies[id.index()];
// A real body always beats a placeholder, whichever crate each
// was seen in, and between two of a kind a local definition
// beats a copy observed from a downstream crate.
let upgrade = match (existing.opaque, body.opaque) {
(true, false) => true,
(false, true) => false,
_ => !existing.local && body.local,
};
if upgrade {
*existing = body;
}
return;
}
let id = FuncId::from_index(self.bodies.len());
self.by_key.insert(body.key.clone(), id);
self.bodies.push(body);
}
/// Creates opaque placeholders for callees nothing ever defined.
fn materialize_missing_callees(&mut self) {
let mut missing: Vec<(FuncKey, String)> = Vec::new();
for body in &self.bodies {
for call in &body.calls {
if let Some(key) = &call.callee
&& !self.by_key.contains_key(key)
{
missing.push((key.clone(), call.callee_display.clone()));
}
}
}
for (key, display) in missing {
if self.by_key.contains_key(&key) {
continue;
}
// The crate can only be guessed from the display path. A
// display that is not a path, drop glue for example, is filed
// as unknown rather than under a crate named after the text.
let krate = display
.split_once("::")
.map(|(first, _)| first)
.filter(|first| {
!first.is_empty()
&& first
.chars()
.all(|c| c.is_alphanumeric() || c == '_')
})
.unwrap_or("unknown")
.to_owned();
self.insert_body(Body::opaque(key, display, krate));
}
}
/// Builds the caller index used to drive the solver's worklist.
fn build_reverse_edges(&mut self) {
self.callers = vec![Vec::new(); self.bodies.len()];
for (i, body) in self.bodies.iter().enumerate() {
let caller = FuncId::from_index(i);
for call in &body.calls {
let Some(key) = &call.callee else { continue };
let Some(&target) = self.by_key.get(key) else {
continue;
};
let list = &mut self.callers[target.index()];
if !list.contains(&caller) {
list.push(caller);
}
}
}
}
/// The number of functions in the graph.
#[must_use]
pub const fn len(&self) -> usize {
self.bodies.len()
}
/// Returns whether the graph holds no functions.
#[must_use]
pub const fn is_empty(&self) -> bool {
self.bodies.is_empty()
}
/// The body behind an index.
#[must_use]
pub fn body(&self, id: FuncId) -> &Body {
&self.bodies[id.index()]
}
/// Every body, with its index.
pub fn iter(&self) -> impl Iterator<Item = (FuncId, &Body)> {
self.bodies
.iter()
.enumerate()
.map(|(i, b)| (FuncId::from_index(i), b))
}
/// Every function defined in the crate under analysis whose body the
/// analysis could read.
pub fn locals(&self) -> impl Iterator<Item = (FuncId, &Body)> {
self.iter().filter(|(_, b)| b.local && !b.opaque)
}
/// Looks a function up by key.
#[must_use]
pub fn id_of(&self, key: &FuncKey) -> Option<FuncId> {
self.by_key.get(key).copied()
}
/// The functions that call `id`.
#[must_use]
pub fn callers(&self, id: FuncId) -> &[FuncId] {
&self.callers[id.index()]
}
/// The build configuration the artifacts were produced under.
#[must_use]
pub const fn config(&self) -> Option<&BuildConfig> {
self.config.as_ref()
}
/// Finds functions whose display path contains `needle`.
///
/// Used to turn a user supplied name into an index without requiring the
/// full mangled symbol. The closest match comes first: a path equal to
/// the needle beats one that merely contains it, and a shorter path beats
/// a longer one, so asking about `parse` explains `parse` rather than the
/// closure inside it.
#[must_use]
pub fn find_by_display(&self, needle: &str) -> Vec<FuncId> {
let mut out: Vec<FuncId> = self
.iter()
.filter(|(_, b)| b.display.contains(needle))
.map(|(id, _)| id)
.collect();
out.sort_by(|a, b| {
let (a, b) = (&self.bodies[a.index()], &self.bodies[b.index()]);
(a.display != needle, a.display.len(), &a.display).cmp(&(
b.display != needle,
b.display.len(),
&b.display,
))
});
out
}
}