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//! One walk over the unit before code generation: which items exist, which
//! variables must live in LSB references, and what each closure captures.
use alloc::collections::{BTreeMap, BTreeSet};
use alloc::vec;
use alloc::vec::Vec;
use hir_lang::{
BinderId, CaptureMode, Control, Event, Expr, ExprId, Hir, IdKind, ItemId, ItemKind, NodeRef,
Pat, Res,
};
/// What code generation needs to know about the whole unit up front.
pub(crate) struct Analysis {
/// Per binder: the variable is shared (captured by reference, aliased by
/// a reference assignment, passed by reference, or a by-reference
/// parameter), so it lives in an LSB reference.
pub(crate) cell: Vec<bool>,
/// Per closure: the outer value binders it uses (implicit captures,
/// transitively through nested closures), in first-use order.
pub(crate) captures: BTreeMap<ExprId, Vec<BinderId>>,
/// Function items, in canonical (pre)order.
pub(crate) fns: Vec<ItemId>,
/// Global and constant items, in canonical order.
pub(crate) globals: Vec<ItemId>,
/// Items the start function may need to run code for (globals,
/// constants, functions with once-evaluated defaults, nested modules),
/// in canonical order.
pub(crate) inits: Vec<ItemId>,
/// Nested modules with a body, in canonical order (their bodies run in
/// the start function).
pub(crate) module_bodies: Vec<ItemId>,
/// The first item kind with code this release does not compile.
pub(crate) unsupported_item: Option<ItemId>,
/// Global items shared by reference (through a `global` alias, a place
/// argument, or a reference assignment): their storage is a reference.
pub(crate) cell_globals: BTreeSet<ItemId>,
/// `let_place` aliases: the place each `Place` binder names, so marking
/// an alias as shared marks the variable behind it.
places: BTreeMap<BinderId, ExprId>,
}
impl Analysis {
pub(crate) fn new(hir: &Hir) -> Self {
let mut a = Analysis {
cell: vec![false; hir.count(IdKind::Binder)],
captures: BTreeMap::new(),
fns: Vec::new(),
globals: Vec::new(),
module_bodies: Vec::new(),
inits: Vec::new(),
unsupported_item: None,
cell_globals: BTreeSet::new(),
places: BTreeMap::new(),
};
let mut aliases: Vec<(BinderId, hir_lang::PathId)> = Vec::new();
let mut by_ref_closures: BTreeSet<ExprId> = BTreeSet::new();
let mut closures = false;
hir.walk_from(NodeRef::Item(hir.root()), |event| {
match event {
Event::Enter(NodeRef::Item(id)) => a.item(hir, id),
Event::Enter(NodeRef::Param(id)) => {
let p = hir.param(id);
if p.by_ref {
if let Pat::Bind { binder, .. } = *hir.pat(p.pat) {
a.mark(binder);
}
}
}
Event::Enter(NodeRef::Expr(id)) => {
closures |= matches!(hir.expr(id), Expr::Closure(_));
a.expr(hir, id, &mut by_ref_closures);
}
Event::Enter(NodeRef::Stmt(id)) => {
if let hir_lang::Stmt::Global { binder, path } = *hir.stmt(id) {
aliases.push((binder, path));
}
}
_ => {}
}
Control::Continue
});
if closures {
for (closure, binders) in hir.all_implicit_captures() {
if by_ref_closures.contains(&closure) {
for &b in &binders {
a.mark(b);
}
}
if !binders.is_empty() {
let _ = a.captures.insert(closure, binders);
}
}
}
for (b, p) in aliases {
if a.cell.get(b.index()).copied().unwrap_or(false) {
a.mark_global(hir, hir.path(p).res);
}
}
a
}
/// Marks the global item a resolution names (in this unit) as shared.
fn mark_global(&mut self, hir: &Hir, res: Res) {
if let Res::Def(d) = res {
if d.unit() == hir.unit() {
if let hir_lang::Def::Item(i) = d.def() {
if matches!(hir.item(i).kind, ItemKind::Global { .. }) {
let _ = self.cell_globals.insert(i);
}
}
}
}
}
fn mark(&mut self, b: BinderId) {
if let Some(slot) = self.cell.get_mut(b.index()) {
*slot = true;
}
}
/// Marks the variable a place names (when it is a variable) as shared:
/// through `let_place` aliases to the variable behind them (bounded by
/// the number of aliases, so a malformed cycle cannot loop).
fn mark_path_local(&mut self, hir: &Hir, e: ExprId) {
let mut e = e;
for _ in 0..=self.places.len() {
let Expr::Path(p) = *hir.expr(e) else {
return;
};
match hir.path(p).res {
Res::Local(b) => match self.places.get(&b) {
Some(&place) => e = place,
None => {
self.mark(b);
return;
}
},
res => {
self.mark_global(hir, res);
return;
}
}
}
}
fn item(&mut self, hir: &Hir, id: ItemId) {
if matches!(
hir.item(id).kind,
ItemKind::Fn(_)
| ItemKind::Global { .. }
| ItemKind::Const { .. }
| ItemKind::Module { .. }
) {
self.inits.push(id);
}
match hir.item(id).kind {
ItemKind::Fn(_) => self.fns.push(id),
ItemKind::Global { .. } | ItemKind::Const { .. } => self.globals.push(id),
ItemKind::Module { body: Some(_), .. } if id != hir.root() => {
self.module_bodies.push(id);
}
ItemKind::Class(_) | ItemKind::Impl(_) | ItemKind::MixinUse(_)
if self.unsupported_item.is_none() =>
{
self.unsupported_item = Some(id);
}
_ => {}
}
}
fn expr(&mut self, hir: &Hir, id: ExprId, by_ref_closures: &mut BTreeSet<ExprId>) {
match *hir.expr(id) {
Expr::Closure(c) => {
if let Some(b) = c.self_binder {
self.mark(b);
}
for cap in hir.list(c.captures) {
if matches!(cap.mode, CaptureMode::ByRef | CaptureMode::ByMutRef) {
if let Res::Local(b) = hir.path(cap.outer).res {
self.mark(b);
}
self.mark(cap.binder);
}
}
// Implicit captures by reference (or inferred, which the
// dynamic profile takes by reference) share the variable.
if matches!(
c.implicit,
Some(CaptureMode::ByRef | CaptureMode::ByMutRef | CaptureMode::Infer)
) {
let _ = by_ref_closures.insert(id);
}
}
Expr::LetPlace { binder, place, .. } => {
let _ = self.places.insert(binder, place);
}
Expr::RefAssign { target, source } => {
self.mark_path_local(hir, target);
self.mark_path_local(hir, source);
}
Expr::Call { args, .. }
| Expr::MethodCall { args, .. }
| Expr::DynMethodCall { args, .. } => {
for arg in hir.list(args) {
if arg.place {
self.mark_path_local(hir, arg.value);
}
}
}
_ => {}
}
}
}