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Only compute vtable information during codegen

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This commit is contained in:
Michael Goulet
2024-06-14 20:35:45 -04:00
parent f8e5660532
commit 3b9adbec32
14 changed files with 141 additions and 195 deletions
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2
compiler/rustc_trait_selection/src/traits/mod.rs
View File

@@ -65,7 +65,7 @@ pub use self::structural_match::search_for_structural_match_violation;
pub use self::structural_normalize::StructurallyNormalizeExt;
pub use self::util::elaborate;
pub use self::util::{expand_trait_aliases, TraitAliasExpander, TraitAliasExpansionInfo};
pub use self::util::{get_vtable_index_of_object_method, impl_item_is_final, upcast_choices};
pub use self::util::{impl_item_is_final, upcast_choices};
pub use self::util::{supertraits, transitive_bounds, transitive_bounds_that_define_assoc_item};
pub use self::util::{with_replaced_escaping_bound_vars, BoundVarReplacer, PlaceholderReplacer};

43
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View File

@@ -22,10 +22,6 @@ use rustc_span::def_id::DefId;
use crate::traits::normalize::{normalize_with_depth, normalize_with_depth_to};
use crate::traits::util::{self, closure_trait_ref_and_return_type};
use crate::traits::vtable::{
count_own_vtable_entries, prepare_vtable_segments, vtable_trait_first_method_offset,
VtblSegment,
};
use crate::traits::{
ImplDerivedCause, ImplSource, ImplSourceUserDefinedData, Normalized, Obligation,
ObligationCause, PolyTraitObligation, PredicateObligation, Selection, SelectionError,
@@ -689,13 +685,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
debug!(?nested, "object nested obligations");
let vtable_base = vtable_trait_first_method_offset(
tcx,
unnormalized_upcast_trait_ref,
ty::Binder::dummy(object_trait_ref),
);
Ok(ImplSource::Builtin(BuiltinImplSource::Object { vtable_base: vtable_base }, nested))
Ok(ImplSource::Builtin(BuiltinImplSource::Object(index), nested))
}
fn confirm_fn_pointer_candidate(
@@ -1125,36 +1115,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
)?
.expect("did not expect ambiguity during confirmation");
let vtable_segment_callback = {
let mut vptr_offset = 0;
move |segment| {
match segment {
VtblSegment::MetadataDSA => {
vptr_offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
vptr_offset += count_own_vtable_entries(tcx, trait_ref);
if trait_ref == unnormalized_upcast_principal {
if emit_vptr {
return ControlFlow::Break(Some(vptr_offset));
} else {
return ControlFlow::Break(None);
}
}
if emit_vptr {
vptr_offset += 1;
}
}
}
ControlFlow::Continue(())
}
};
let vtable_vptr_slot =
prepare_vtable_segments(tcx, source_principal, vtable_segment_callback).unwrap();
Ok(ImplSource::Builtin(BuiltinImplSource::TraitUpcasting { vtable_vptr_slot }, nested))
Ok(ImplSource::Builtin(BuiltinImplSource::TraitUpcasting, nested))
}
fn confirm_builtin_unsize_candidate(

17
compiler/rustc_trait_selection/src/traits/util.rs
View File

@@ -208,23 +208,6 @@ pub fn upcast_choices<'tcx>(
supertraits(tcx, source_trait_ref).filter(|r| r.def_id() == target_trait_def_id).collect()
}
/// Given an upcast trait object described by `object`, returns the
/// index of the method `method_def_id` (which should be part of
/// `object.upcast_trait_ref`) within the vtable for `object`.
pub fn get_vtable_index_of_object_method<'tcx>(
tcx: TyCtxt<'tcx>,
vtable_base: usize,
method_def_id: DefId,
) -> Option<usize> {
// Count number of methods preceding the one we are selecting and
// add them to the total offset.
tcx.own_existential_vtable_entries(tcx.parent(method_def_id))
.iter()
.copied()
.position(|def_id| def_id == method_def_id)
.map(|index| vtable_base + index)
}
pub fn closure_trait_ref_and_return_type<'tcx>(
tcx: TyCtxt<'tcx>,
fn_trait_def_id: DefId,

127
compiler/rustc_trait_selection/src/traits/vtable.rs
View File

@@ -1,15 +1,11 @@
use crate::errors::DumpVTableEntries;
use crate::traits::{impossible_predicates, is_vtable_safe_method};
use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_infer::traits::util::PredicateSet;
use rustc_infer::traits::ImplSource;
use rustc_middle::bug;
use rustc_middle::query::Providers;
use rustc_middle::traits::BuiltinImplSource;
use rustc_middle::ty::visit::TypeVisitableExt;
use rustc_middle::ty::GenericArgs;
use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt, Upcast, VtblEntry};
use rustc_middle::ty::{GenericArgs, TypeVisitableExt};
use rustc_span::{sym, Span};
use smallvec::{smallvec, SmallVec};
@@ -320,30 +316,42 @@ fn vtable_entries<'tcx>(
tcx.arena.alloc_from_iter(entries)
}
/// Find slot base for trait methods within vtable entries of another trait
pub(super) fn vtable_trait_first_method_offset<'tcx>(
tcx: TyCtxt<'tcx>,
trait_to_be_found: ty::PolyTraitRef<'tcx>,
trait_owning_vtable: ty::PolyTraitRef<'tcx>,
) -> usize {
// #90177
let trait_to_be_found_erased = tcx.erase_regions(trait_to_be_found);
// Given a `dyn Subtrait: Supertrait` trait ref, find corresponding first slot
// for `Supertrait`'s methods in the vtable of `Subtrait`.
pub(crate) fn first_method_vtable_slot<'tcx>(tcx: TyCtxt<'tcx>, key: ty::TraitRef<'tcx>) -> usize {
debug_assert!(!key.has_non_region_infer() && !key.has_non_region_param());
let ty::Dynamic(source, _, _) = *key.self_ty().kind() else {
bug!();
};
let source_principal = tcx
.normalize_erasing_regions(ty::ParamEnv::reveal_all(), source.principal().unwrap())
.with_self_ty(tcx, tcx.types.trait_object_dummy_self);
let target_principal = tcx
.normalize_erasing_regions(ty::ParamEnv::reveal_all(), key)
// We don't care about the self type, since it will always be the same thing.
.with_self_ty(tcx, tcx.types.trait_object_dummy_self);
let vtable_segment_callback = {
let mut vtable_base = 0;
let mut vptr_offset = 0;
move |segment| {
match segment {
VtblSegment::MetadataDSA => {
vtable_base += TyCtxt::COMMON_VTABLE_ENTRIES.len();
vptr_offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
if tcx.erase_regions(trait_ref) == trait_to_be_found_erased {
return ControlFlow::Break(vtable_base);
if tcx
.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), trait_ref)
== target_principal
{
return ControlFlow::Break(vptr_offset);
}
vtable_base += count_own_vtable_entries(tcx, trait_ref);
vptr_offset += tcx.own_existential_vtable_entries(trait_ref.def_id()).len();
if emit_vptr {
vtable_base += 1;
vptr_offset += 1;
}
}
}
@@ -351,55 +359,72 @@ pub(super) fn vtable_trait_first_method_offset<'tcx>(
}
};
if let Some(vtable_base) =
prepare_vtable_segments(tcx, trait_owning_vtable, vtable_segment_callback)
{
vtable_base
} else {
bug!("Failed to find info for expected trait in vtable");
}
prepare_vtable_segments(tcx, source_principal, vtable_segment_callback).unwrap()
}
/// Find slot offset for trait vptr within vtable entries of another trait
pub(crate) fn vtable_trait_upcasting_coercion_new_vptr_slot<'tcx>(
/// Given a `dyn Subtrait` and `dyn Supertrait` trait object, find the slot of
/// // the trait vptr in the subtrait's vtable.
pub(crate) fn supertrait_vtable_slot<'tcx>(
tcx: TyCtxt<'tcx>,
key: (
Ty<'tcx>, // trait object type whose trait owning vtable
Ty<'tcx>, // trait object for supertrait
Ty<'tcx>, // Source -- `dyn Subtrait`.
Ty<'tcx>, // Target -- `dyn Supertrait` being coerced to.
),
) -> Option<usize> {
debug_assert!(!key.has_non_region_infer() && !key.has_non_region_param());
let (source, target) = key;
assert!(matches!(&source.kind(), &ty::Dynamic(..)) && !source.has_infer());
assert!(matches!(&target.kind(), &ty::Dynamic(..)) && !target.has_infer());
let ty::Dynamic(source, _, _) = *source.kind() else {
bug!();
};
let source_principal = tcx
.normalize_erasing_regions(ty::ParamEnv::reveal_all(), source.principal().unwrap())
.with_self_ty(tcx, tcx.types.trait_object_dummy_self);
// this has been typecked-before, so diagnostics is not really needed.
let unsize_trait_did = tcx.require_lang_item(LangItem::Unsize, None);
let ty::Dynamic(target, _, _) = *target.kind() else {
bug!();
};
let target_principal = tcx
.normalize_erasing_regions(ty::ParamEnv::reveal_all(), target.principal().unwrap())
.with_self_ty(tcx, tcx.types.trait_object_dummy_self);
let trait_ref = ty::TraitRef::new(tcx, unsize_trait_did, [source, target]);
let vtable_segment_callback = {
let mut vptr_offset = 0;
move |segment| {
match segment {
VtblSegment::MetadataDSA => {
vptr_offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
}
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
vptr_offset += tcx.own_existential_vtable_entries(trait_ref.def_id()).len();
if tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), trait_ref)
== target_principal
{
if emit_vptr {
return ControlFlow::Break(Some(vptr_offset));
} else {
return ControlFlow::Break(None);
}
}
match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), trait_ref)) {
Ok(ImplSource::Builtin(BuiltinImplSource::TraitUpcasting { vtable_vptr_slot }, _)) => {
*vtable_vptr_slot
if emit_vptr {
vptr_offset += 1;
}
}
}
ControlFlow::Continue(())
}
otherwise => bug!("expected TraitUpcasting candidate, got {otherwise:?}"),
}
}
};
/// Given a trait `trait_ref`, returns the number of vtable entries
/// that come from `trait_ref`, excluding its supertraits. Used in
/// computing the vtable base for an upcast trait of a trait object.
pub(crate) fn count_own_vtable_entries<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
) -> usize {
tcx.own_existential_vtable_entries(trait_ref.def_id()).len()
prepare_vtable_segments(tcx, source_principal, vtable_segment_callback).unwrap()
}
pub(super) fn provide(providers: &mut Providers) {
*providers = Providers {
own_existential_vtable_entries,
vtable_entries,
vtable_trait_upcasting_coercion_new_vptr_slot,
first_method_vtable_slot,
supertrait_vtable_slot,
..*providers
};
}