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has vtable analysis #850
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,186 @@ | ||
| //! Determining which types has vtable | ||
| use super::{ConstrainResult, MonotoneFramework}; | ||
| use std::collections::HashSet; | ||
| use std::collections::HashMap; | ||
| use ir::context::{BindgenContext, ItemId}; | ||
| use ir::traversal::EdgeKind; | ||
| use ir::ty::TypeKind; | ||
| use ir::traversal::Trace; | ||
|
|
||
| /// An analysis that finds for each IR item whether it has vtable or not | ||
| /// | ||
| /// We use the monotone function `has vtable`, defined as follows: | ||
| /// | ||
| /// * If T is a type alias, a templated alias, an indirection to another type, | ||
| /// or a reference of a type, T has vtable if the type T refers to has vtable. | ||
| /// * If T is a compound type, T has vtable if we saw a virtual function when | ||
| /// parsing it or any of its base member has vtable. | ||
| /// * If T is an instantiation of an abstract template definition, T has | ||
| /// vtable if template definition has vtable | ||
| #[derive(Debug, Clone)] | ||
| pub struct HasVtableAnalysis<'ctx, 'gen> | ||
| where 'gen: 'ctx | ||
| { | ||
| ctx: &'ctx BindgenContext<'gen>, | ||
|
|
||
| // The incremental result of this analysis's computation. Everything in this | ||
| // set definitely has a vtable. | ||
| have_vtable: HashSet<ItemId>, | ||
|
|
||
| // Dependencies saying that if a key ItemId has been inserted into the | ||
| // `have_vtable` set, then each of the ids in Vec<ItemId> need to be | ||
| // considered again. | ||
| // | ||
| // This is a subset of the natural IR graph with reversed edges, where we | ||
| // only include the edges from the IR graph that can affect whether a type | ||
| // has a vtable or not. | ||
| dependencies: HashMap<ItemId, Vec<ItemId>>, | ||
| } | ||
|
|
||
| impl<'ctx, 'gen> HasVtableAnalysis<'ctx, 'gen> { | ||
| fn consider_edge(kind: EdgeKind) -> bool { | ||
| match kind { | ||
| // These are the only edges that can affect whether a type has a | ||
| // vtable or not. | ||
| EdgeKind::TypeReference | | ||
| EdgeKind::BaseMember | | ||
| EdgeKind::TemplateDeclaration => true, | ||
| _ => false, | ||
| } | ||
| } | ||
|
|
||
| fn insert(&mut self, id: ItemId) -> ConstrainResult { | ||
| let was_not_already_in_set = self.have_vtable.insert(id); | ||
| assert!( | ||
| was_not_already_in_set, | ||
| "We shouldn't try and insert {:?} twice because if it was \ | ||
| already in the set, `constrain` should have exited early.", | ||
| id | ||
| ); | ||
| ConstrainResult::Changed | ||
| } | ||
| } | ||
|
|
||
| impl<'ctx, 'gen> MonotoneFramework for HasVtableAnalysis<'ctx, 'gen> { | ||
| type Node = ItemId; | ||
| type Extra = &'ctx BindgenContext<'gen>; | ||
| type Output = HashSet<ItemId>; | ||
|
|
||
| fn new(ctx: &'ctx BindgenContext<'gen>) -> HasVtableAnalysis<'ctx, 'gen> { | ||
| let have_vtable = HashSet::new(); | ||
| let mut dependencies = HashMap::new(); | ||
|
|
||
| for &item in ctx.whitelisted_items() { | ||
| dependencies.entry(item).or_insert(vec![]); | ||
|
|
||
| { | ||
| // We reverse our natural IR graph edges to find dependencies | ||
| // between nodes. | ||
| item.trace(ctx, &mut |sub_item: ItemId, edge_kind| { | ||
| if ctx.whitelisted_items().contains(&sub_item) && | ||
| Self::consider_edge(edge_kind) { | ||
| dependencies.entry(sub_item) | ||
| .or_insert(vec![]) | ||
| .push(item); | ||
| } | ||
| }, &()); | ||
| } | ||
| } | ||
|
|
||
| HasVtableAnalysis { | ||
| ctx, | ||
| have_vtable, | ||
| dependencies, | ||
| } | ||
| } | ||
|
|
||
| fn initial_worklist(&self) -> Vec<ItemId> { | ||
| self.ctx.whitelisted_items().iter().cloned().collect() | ||
| } | ||
|
|
||
| fn constrain(&mut self, id: ItemId) -> ConstrainResult { | ||
| if self.have_vtable.contains(&id) { | ||
| // We've already computed that this type has a vtable and that can't | ||
| // change. | ||
| return ConstrainResult::Same; | ||
| } | ||
|
|
||
| let item = self.ctx.resolve_item(id); | ||
| let ty = match item.as_type() { | ||
| None => return ConstrainResult::Same, | ||
| Some(ty) => ty | ||
| }; | ||
|
|
||
| // TODO #851: figure out a way to handle deriving from template type parameters. | ||
| match *ty.kind() { | ||
| TypeKind::TemplateAlias(t, _) | | ||
| TypeKind::Alias(t) | | ||
| TypeKind::ResolvedTypeRef(t) | | ||
| TypeKind::Reference(t) => { | ||
| if self.have_vtable.contains(&t) { | ||
| self.insert(id) | ||
| } else { | ||
| ConstrainResult::Same | ||
| } | ||
| }, | ||
|
|
||
| TypeKind::Comp(ref info) => { | ||
| if info.has_own_virtual_method() { | ||
| return self.insert(id); | ||
| } | ||
| let bases_has_vtable = info.base_members().iter().any(|base| { | ||
| self.have_vtable.contains(&base.ty) | ||
| }); | ||
| if bases_has_vtable { | ||
| self.insert(id) | ||
| } else { | ||
| ConstrainResult::Same | ||
| } | ||
| }, | ||
|
|
||
| TypeKind::TemplateInstantiation(ref inst) => { | ||
| if self.have_vtable.contains(&inst.template_definition()) { | ||
| self.insert(id) | ||
| } else { | ||
| ConstrainResult::Same | ||
| } | ||
| }, | ||
|
|
||
| _ => ConstrainResult::Same, | ||
| } | ||
| } | ||
|
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||
| fn each_depending_on<F>(&self, id: ItemId, mut f: F) | ||
| where F: FnMut(ItemId), | ||
| { | ||
| if let Some(edges) = self.dependencies.get(&id) { | ||
| for item in edges { | ||
| trace!("enqueue {:?} into worklist", item); | ||
| f(*item); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'ctx, 'gen> From<HasVtableAnalysis<'ctx, 'gen>> for HashSet<ItemId> { | ||
| fn from(analysis: HasVtableAnalysis<'ctx, 'gen>) -> Self { | ||
| analysis.have_vtable | ||
| } | ||
| } | ||
|
|
||
| /// A convenience trait for the things for which we might wonder if they have a | ||
| /// vtable during codegen. | ||
| /// | ||
| /// This is not for _computing_ whether the thing has a vtable, it is for | ||
| /// looking up the results of the HasVtableAnalysis's computations for a | ||
| /// specific thing. | ||
| pub trait HasVtable { | ||
|
|
||
| /// Implementations can define this type to get access to any extra | ||
| /// information required to determine whether they have vtable. If | ||
| /// extra information is unneeded, then this should simply be the unit type. | ||
| type Extra; | ||
|
|
||
| /// Return `true` if this thing has vtable, `false` otherwise. | ||
| fn has_vtable(&self, ctx: &BindgenContext, extra: &Self::Extra) -> bool; | ||
| } | ||
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Want to do a follow up PR to pull the creation of the dependencies graph out and share its definition between all of our analyses? This is getting copied with slight changes a little too much now, and its clear we need a helper function.
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Sure.