Move vtable methods into its own module
This commit is contained in:
Michael Goulet
parent
48270044b0
commit
b36035c20f
4 changed files with 398 additions and 378 deletions
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@ -20,9 +20,9 @@ mod select;
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mod specialize;
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mod specialize;
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mod structural_match;
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mod structural_match;
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mod util;
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mod util;
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mod vtable;
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pub mod wf;
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pub mod wf;
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use crate::errors::DumpVTableEntries;
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use crate::infer::outlives::env::OutlivesEnvironment;
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use crate::infer::outlives::env::OutlivesEnvironment;
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use crate::infer::{InferCtxt, TyCtxtInferExt};
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use crate::infer::{InferCtxt, TyCtxtInferExt};
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use crate::traits::error_reporting::TypeErrCtxtExt as _;
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use crate::traits::error_reporting::TypeErrCtxtExt as _;
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@ -30,15 +30,11 @@ use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
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use rustc_errors::ErrorGuaranteed;
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use rustc_errors::ErrorGuaranteed;
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use rustc_hir as hir;
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use rustc_hir as hir;
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use rustc_hir::def_id::DefId;
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use rustc_hir::def_id::DefId;
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use rustc_hir::lang_items::LangItem;
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use rustc_middle::ty::fold::TypeFoldable;
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use rustc_middle::ty::fold::TypeFoldable;
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use rustc_middle::ty::visit::TypeVisitable;
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use rustc_middle::ty::visit::TypeVisitable;
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use rustc_middle::ty::{
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use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeSuperVisitable};
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self, DefIdTree, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeSuperVisitable, VtblEntry,
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};
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use rustc_middle::ty::{InternalSubsts, SubstsRef};
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use rustc_middle::ty::{InternalSubsts, SubstsRef};
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use rustc_span::{sym, Span};
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use rustc_span::Span;
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use smallvec::SmallVec;
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use std::fmt::Debug;
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use std::fmt::Debug;
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use std::ops::ControlFlow;
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use std::ops::ControlFlow;
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@ -567,368 +563,13 @@ fn is_impossible_method<'tcx>(
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false
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false
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}
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}
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#[derive(Clone, Debug)]
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enum VtblSegment<'tcx> {
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MetadataDSA,
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TraitOwnEntries { trait_ref: ty::PolyTraitRef<'tcx>, emit_vptr: bool },
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}
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/// Prepare the segments for a vtable
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fn prepare_vtable_segments<'tcx, T>(
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tcx: TyCtxt<'tcx>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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mut segment_visitor: impl FnMut(VtblSegment<'tcx>) -> ControlFlow<T>,
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) -> Option<T> {
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// The following constraints holds for the final arrangement.
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// 1. The whole virtual table of the first direct super trait is included as the
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// the prefix. If this trait doesn't have any super traits, then this step
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// consists of the dsa metadata.
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// 2. Then comes the proper pointer metadata(vptr) and all own methods for all
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// other super traits except those already included as part of the first
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// direct super trait virtual table.
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// 3. finally, the own methods of this trait.
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// This has the advantage that trait upcasting to the first direct super trait on each level
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// is zero cost, and to another trait includes only replacing the pointer with one level indirection,
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// while not using too much extra memory.
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// For a single inheritance relationship like this,
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// D --> C --> B --> A
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// The resulting vtable will consists of these segments:
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// DSA, A, B, C, D
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// For a multiple inheritance relationship like this,
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// D --> C --> A
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// \-> B
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// The resulting vtable will consists of these segments:
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// DSA, A, B, B-vptr, C, D
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// For a diamond inheritance relationship like this,
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// D --> B --> A
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// \-> C -/
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// The resulting vtable will consists of these segments:
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// DSA, A, B, C, C-vptr, D
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// For a more complex inheritance relationship like this:
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// O --> G --> C --> A
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// \ \ \-> B
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// | |-> F --> D
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// | \-> E
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// |-> N --> J --> H
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// \ \-> I
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// |-> M --> K
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// \-> L
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// The resulting vtable will consists of these segments:
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// DSA, A, B, B-vptr, C, D, D-vptr, E, E-vptr, F, F-vptr, G,
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// H, H-vptr, I, I-vptr, J, J-vptr, K, K-vptr, L, L-vptr, M, M-vptr,
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// N, N-vptr, O
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// emit dsa segment first.
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if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::MetadataDSA) {
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return Some(v);
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}
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let mut emit_vptr_on_new_entry = false;
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let mut visited = util::PredicateSet::new(tcx);
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let predicate = trait_ref.without_const().to_predicate(tcx);
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let mut stack: SmallVec<[(ty::PolyTraitRef<'tcx>, _, _); 5]> =
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smallvec![(trait_ref, emit_vptr_on_new_entry, None)];
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visited.insert(predicate);
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// the main traversal loop:
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// basically we want to cut the inheritance directed graph into a few non-overlapping slices of nodes
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// that each node is emitted after all its descendents have been emitted.
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// so we convert the directed graph into a tree by skipping all previously visited nodes using a visited set.
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// this is done on the fly.
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// Each loop run emits a slice - it starts by find a "childless" unvisited node, backtracking upwards, and it
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// stops after it finds a node that has a next-sibling node.
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// This next-sibling node will used as the starting point of next slice.
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// Example:
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// For a diamond inheritance relationship like this,
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// D#1 --> B#0 --> A#0
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// \-> C#1 -/
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// Starting point 0 stack [D]
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// Loop run #0: Stack after diving in is [D B A], A is "childless"
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// after this point, all newly visited nodes won't have a vtable that equals to a prefix of this one.
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// Loop run #0: Emitting the slice [B A] (in reverse order), B has a next-sibling node, so this slice stops here.
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// Loop run #0: Stack after exiting out is [D C], C is the next starting point.
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// Loop run #1: Stack after diving in is [D C], C is "childless", since its child A is skipped(already emitted).
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// Loop run #1: Emitting the slice [D C] (in reverse order). No one has a next-sibling node.
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// Loop run #1: Stack after exiting out is []. Now the function exits.
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loop {
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// dive deeper into the stack, recording the path
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'diving_in: loop {
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if let Some((inner_most_trait_ref, _, _)) = stack.last() {
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let inner_most_trait_ref = *inner_most_trait_ref;
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let mut direct_super_traits_iter = tcx
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.super_predicates_of(inner_most_trait_ref.def_id())
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.predicates
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.into_iter()
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.filter_map(move |(pred, _)| {
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pred.subst_supertrait(tcx, &inner_most_trait_ref).to_opt_poly_trait_pred()
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});
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'diving_in_skip_visited_traits: loop {
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if let Some(next_super_trait) = direct_super_traits_iter.next() {
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if visited.insert(next_super_trait.to_predicate(tcx)) {
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// We're throwing away potential constness of super traits here.
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// FIXME: handle ~const super traits
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let next_super_trait = next_super_trait.map_bound(|t| t.trait_ref);
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stack.push((
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next_super_trait,
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emit_vptr_on_new_entry,
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Some(direct_super_traits_iter),
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));
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break 'diving_in_skip_visited_traits;
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} else {
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continue 'diving_in_skip_visited_traits;
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}
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} else {
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break 'diving_in;
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}
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}
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}
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}
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// Other than the left-most path, vptr should be emitted for each trait.
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emit_vptr_on_new_entry = true;
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// emit innermost item, move to next sibling and stop there if possible, otherwise jump to outer level.
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'exiting_out: loop {
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if let Some((inner_most_trait_ref, emit_vptr, siblings_opt)) = stack.last_mut() {
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if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::TraitOwnEntries {
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trait_ref: *inner_most_trait_ref,
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emit_vptr: *emit_vptr,
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}) {
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return Some(v);
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}
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'exiting_out_skip_visited_traits: loop {
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if let Some(siblings) = siblings_opt {
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if let Some(next_inner_most_trait_ref) = siblings.next() {
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if visited.insert(next_inner_most_trait_ref.to_predicate(tcx)) {
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// We're throwing away potential constness of super traits here.
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// FIXME: handle ~const super traits
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let next_inner_most_trait_ref =
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next_inner_most_trait_ref.map_bound(|t| t.trait_ref);
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*inner_most_trait_ref = next_inner_most_trait_ref;
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*emit_vptr = emit_vptr_on_new_entry;
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break 'exiting_out;
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} else {
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continue 'exiting_out_skip_visited_traits;
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}
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}
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}
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stack.pop();
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continue 'exiting_out;
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}
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}
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// all done
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return None;
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}
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}
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}
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fn dump_vtable_entries<'tcx>(
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tcx: TyCtxt<'tcx>,
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sp: Span,
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trait_ref: ty::PolyTraitRef<'tcx>,
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entries: &[VtblEntry<'tcx>],
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) {
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tcx.sess.emit_err(DumpVTableEntries {
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span: sp,
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trait_ref,
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entries: format!("{:#?}", entries),
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});
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}
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fn own_existential_vtable_entries<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId) -> &'tcx [DefId] {
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let trait_methods = tcx
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.associated_items(trait_def_id)
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.in_definition_order()
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.filter(|item| item.kind == ty::AssocKind::Fn);
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// Now list each method's DefId (for within its trait).
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let own_entries = trait_methods.filter_map(move |trait_method| {
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debug!("own_existential_vtable_entry: trait_method={:?}", trait_method);
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let def_id = trait_method.def_id;
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// Some methods cannot be called on an object; skip those.
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if !is_vtable_safe_method(tcx, trait_def_id, &trait_method) {
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debug!("own_existential_vtable_entry: not vtable safe");
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return None;
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}
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Some(def_id)
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});
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tcx.arena.alloc_from_iter(own_entries.into_iter())
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}
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/// Given a trait `trait_ref`, iterates the vtable entries
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/// that come from `trait_ref`, including its supertraits.
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fn vtable_entries<'tcx>(
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tcx: TyCtxt<'tcx>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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) -> &'tcx [VtblEntry<'tcx>] {
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debug!("vtable_entries({:?})", trait_ref);
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let mut entries = vec![];
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let vtable_segment_callback = |segment| -> ControlFlow<()> {
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match segment {
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VtblSegment::MetadataDSA => {
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entries.extend(TyCtxt::COMMON_VTABLE_ENTRIES);
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}
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VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
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let existential_trait_ref = trait_ref
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.map_bound(|trait_ref| ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref));
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// Lookup the shape of vtable for the trait.
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let own_existential_entries =
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tcx.own_existential_vtable_entries(existential_trait_ref.def_id());
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let own_entries = own_existential_entries.iter().copied().map(|def_id| {
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debug!("vtable_entries: trait_method={:?}", def_id);
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// The method may have some early-bound lifetimes; add regions for those.
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let substs = trait_ref.map_bound(|trait_ref| {
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InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
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GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
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GenericParamDefKind::Type { .. }
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| GenericParamDefKind::Const { .. } => {
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trait_ref.substs[param.index as usize]
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}
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})
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});
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// The trait type may have higher-ranked lifetimes in it;
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// erase them if they appear, so that we get the type
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// at some particular call site.
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let substs = tcx
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.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), substs);
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// It's possible that the method relies on where-clauses that
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// do not hold for this particular set of type parameters.
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// Note that this method could then never be called, so we
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// do not want to try and codegen it, in that case (see #23435).
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let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
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if impossible_predicates(tcx, predicates.predicates) {
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debug!("vtable_entries: predicates do not hold");
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return VtblEntry::Vacant;
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}
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let instance = ty::Instance::resolve_for_vtable(
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tcx,
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ty::ParamEnv::reveal_all(),
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def_id,
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substs,
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)
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.expect("resolution failed during building vtable representation");
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VtblEntry::Method(instance)
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});
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entries.extend(own_entries);
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if emit_vptr {
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entries.push(VtblEntry::TraitVPtr(trait_ref));
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}
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}
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}
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ControlFlow::Continue(())
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};
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let _ = prepare_vtable_segments(tcx, trait_ref, vtable_segment_callback);
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if tcx.has_attr(trait_ref.def_id(), sym::rustc_dump_vtable) {
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let sp = tcx.def_span(trait_ref.def_id());
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dump_vtable_entries(tcx, sp, trait_ref, &entries);
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}
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tcx.arena.alloc_from_iter(entries.into_iter())
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}
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/// Find slot base for trait methods within vtable entries of another trait
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fn vtable_trait_first_method_offset<'tcx>(
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tcx: TyCtxt<'tcx>,
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key: (
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ty::PolyTraitRef<'tcx>, // trait_to_be_found
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ty::PolyTraitRef<'tcx>, // trait_owning_vtable
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),
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) -> usize {
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let (trait_to_be_found, trait_owning_vtable) = key;
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// #90177
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let trait_to_be_found_erased = tcx.erase_regions(trait_to_be_found);
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let vtable_segment_callback = {
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let mut vtable_base = 0;
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move |segment| {
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match segment {
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VtblSegment::MetadataDSA => {
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vtable_base += TyCtxt::COMMON_VTABLE_ENTRIES.len();
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}
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VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
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if tcx.erase_regions(trait_ref) == trait_to_be_found_erased {
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return ControlFlow::Break(vtable_base);
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}
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|
||||||
vtable_base += util::count_own_vtable_entries(tcx, trait_ref);
|
|
||||||
if emit_vptr {
|
|
||||||
vtable_base += 1;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
ControlFlow::Continue(())
|
|
||||||
}
|
|
||||||
};
|
|
||||||
|
|
||||||
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");
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
/// Find slot offset for trait vptr within vtable entries of another trait
|
|
||||||
pub fn vtable_trait_upcasting_coercion_new_vptr_slot<'tcx>(
|
|
||||||
tcx: TyCtxt<'tcx>,
|
|
||||||
key: (
|
|
||||||
Ty<'tcx>, // trait object type whose trait owning vtable
|
|
||||||
Ty<'tcx>, // trait object for supertrait
|
|
||||||
),
|
|
||||||
) -> Option<usize> {
|
|
||||||
let (source, target) = key;
|
|
||||||
assert!(matches!(&source.kind(), &ty::Dynamic(..)) && !source.needs_infer());
|
|
||||||
assert!(matches!(&target.kind(), &ty::Dynamic(..)) && !target.needs_infer());
|
|
||||||
|
|
||||||
// this has been typecked-before, so diagnostics is not really needed.
|
|
||||||
let unsize_trait_did = tcx.require_lang_item(LangItem::Unsize, None);
|
|
||||||
|
|
||||||
let trait_ref = tcx.mk_trait_ref(unsize_trait_did, [source, target]);
|
|
||||||
|
|
||||||
match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), ty::Binder::dummy(trait_ref))) {
|
|
||||||
Ok(ImplSource::TraitUpcasting(implsrc_traitcasting)) => {
|
|
||||||
implsrc_traitcasting.vtable_vptr_slot
|
|
||||||
}
|
|
||||||
otherwise => bug!("expected TraitUpcasting candidate, got {otherwise:?}"),
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
pub fn provide(providers: &mut ty::query::Providers) {
|
pub fn provide(providers: &mut ty::query::Providers) {
|
||||||
object_safety::provide(providers);
|
object_safety::provide(providers);
|
||||||
|
vtable::provide(providers);
|
||||||
*providers = ty::query::Providers {
|
*providers = ty::query::Providers {
|
||||||
specialization_graph_of: specialize::specialization_graph_provider,
|
specialization_graph_of: specialize::specialization_graph_provider,
|
||||||
specializes: specialize::specializes,
|
specializes: specialize::specializes,
|
||||||
codegen_select_candidate: codegen::codegen_select_candidate,
|
codegen_select_candidate: codegen::codegen_select_candidate,
|
||||||
own_existential_vtable_entries,
|
|
||||||
vtable_entries,
|
|
||||||
vtable_trait_upcasting_coercion_new_vptr_slot,
|
|
||||||
subst_and_check_impossible_predicates,
|
subst_and_check_impossible_predicates,
|
||||||
is_impossible_method,
|
is_impossible_method,
|
||||||
..*providers
|
..*providers
|
||||||
|
|
|
||||||
|
|
@ -19,6 +19,10 @@ use rustc_span::def_id::DefId;
|
||||||
|
|
||||||
use crate::traits::project::{normalize_with_depth, normalize_with_depth_to};
|
use crate::traits::project::{normalize_with_depth, normalize_with_depth_to};
|
||||||
use crate::traits::util::{self, closure_trait_ref_and_return_type, predicate_for_trait_def};
|
use crate::traits::util::{self, closure_trait_ref_and_return_type, predicate_for_trait_def};
|
||||||
|
use crate::traits::vtable::{
|
||||||
|
count_own_vtable_entries, prepare_vtable_segments, vtable_trait_first_method_offset,
|
||||||
|
VtblSegment,
|
||||||
|
};
|
||||||
use crate::traits::{
|
use crate::traits::{
|
||||||
BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
|
BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
|
||||||
ImplSourceAutoImplData, ImplSourceBuiltinData, ImplSourceClosureData,
|
ImplSourceAutoImplData, ImplSourceBuiltinData, ImplSourceClosureData,
|
||||||
|
|
@ -26,7 +30,7 @@ use crate::traits::{
|
||||||
ImplSourceGeneratorData, ImplSourceObjectData, ImplSourceTraitAliasData,
|
ImplSourceGeneratorData, ImplSourceObjectData, ImplSourceTraitAliasData,
|
||||||
ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized, ObjectCastObligation,
|
ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized, ObjectCastObligation,
|
||||||
Obligation, ObligationCause, OutputTypeParameterMismatch, PredicateObligation, Selection,
|
Obligation, ObligationCause, OutputTypeParameterMismatch, PredicateObligation, Selection,
|
||||||
SelectionError, TraitNotObjectSafe, TraitObligation, Unimplemented, VtblSegment,
|
SelectionError, TraitNotObjectSafe, TraitObligation, Unimplemented,
|
||||||
};
|
};
|
||||||
|
|
||||||
use super::BuiltinImplConditions;
|
use super::BuiltinImplConditions;
|
||||||
|
|
@ -583,7 +587,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
|
||||||
|
|
||||||
debug!(?nested, "object nested obligations");
|
debug!(?nested, "object nested obligations");
|
||||||
|
|
||||||
let vtable_base = super::super::vtable_trait_first_method_offset(
|
let vtable_base = vtable_trait_first_method_offset(
|
||||||
tcx,
|
tcx,
|
||||||
(unnormalized_upcast_trait_ref, ty::Binder::dummy(object_trait_ref)),
|
(unnormalized_upcast_trait_ref, ty::Binder::dummy(object_trait_ref)),
|
||||||
);
|
);
|
||||||
|
|
@ -904,7 +908,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
|
||||||
vptr_offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
|
vptr_offset += TyCtxt::COMMON_VTABLE_ENTRIES.len();
|
||||||
}
|
}
|
||||||
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
|
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
|
||||||
vptr_offset += util::count_own_vtable_entries(tcx, trait_ref);
|
vptr_offset += count_own_vtable_entries(tcx, trait_ref);
|
||||||
if trait_ref == upcast_trait_ref {
|
if trait_ref == upcast_trait_ref {
|
||||||
if emit_vptr {
|
if emit_vptr {
|
||||||
return ControlFlow::Break(Some(vptr_offset));
|
return ControlFlow::Break(Some(vptr_offset));
|
||||||
|
|
@ -923,8 +927,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
|
||||||
};
|
};
|
||||||
|
|
||||||
let vtable_vptr_slot =
|
let vtable_vptr_slot =
|
||||||
super::super::prepare_vtable_segments(tcx, source_trait_ref, vtable_segment_callback)
|
prepare_vtable_segments(tcx, source_trait_ref, vtable_segment_callback).unwrap();
|
||||||
.unwrap();
|
|
||||||
|
|
||||||
Ok(ImplSourceTraitUpcastingData { upcast_trait_ref, vtable_vptr_slot, nested })
|
Ok(ImplSourceTraitUpcastingData { upcast_trait_ref, vtable_vptr_slot, nested })
|
||||||
}
|
}
|
||||||
|
|
|
||||||
|
|
@ -261,16 +261,6 @@ pub fn upcast_choices<'tcx>(
|
||||||
supertraits(tcx, source_trait_ref).filter(|r| r.def_id() == target_trait_def_id).collect()
|
supertraits(tcx, source_trait_ref).filter(|r| r.def_id() == target_trait_def_id).collect()
|
||||||
}
|
}
|
||||||
|
|
||||||
/// 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 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()
|
|
||||||
}
|
|
||||||
|
|
||||||
/// Given an upcast trait object described by `object`, returns the
|
/// Given an upcast trait object described by `object`, returns the
|
||||||
/// index of the method `method_def_id` (which should be part of
|
/// index of the method `method_def_id` (which should be part of
|
||||||
/// `object.upcast_trait_ref`) within the vtable for `object`.
|
/// `object.upcast_trait_ref`) within the vtable for `object`.
|
||||||
|
|
|
||||||
386
compiler/rustc_trait_selection/src/traits/vtable.rs
Normal file
386
compiler/rustc_trait_selection/src/traits/vtable.rs
Normal file
|
|
@ -0,0 +1,386 @@
|
||||||
|
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::ty::visit::TypeVisitable;
|
||||||
|
use rustc_middle::ty::InternalSubsts;
|
||||||
|
use rustc_middle::ty::{self, GenericParamDefKind, ToPredicate, Ty, TyCtxt, VtblEntry};
|
||||||
|
use rustc_span::{sym, Span};
|
||||||
|
use smallvec::SmallVec;
|
||||||
|
|
||||||
|
use std::fmt::Debug;
|
||||||
|
use std::ops::ControlFlow;
|
||||||
|
|
||||||
|
#[derive(Clone, Debug)]
|
||||||
|
pub(super) enum VtblSegment<'tcx> {
|
||||||
|
MetadataDSA,
|
||||||
|
TraitOwnEntries { trait_ref: ty::PolyTraitRef<'tcx>, emit_vptr: bool },
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Prepare the segments for a vtable
|
||||||
|
pub(super) fn prepare_vtable_segments<'tcx, T>(
|
||||||
|
tcx: TyCtxt<'tcx>,
|
||||||
|
trait_ref: ty::PolyTraitRef<'tcx>,
|
||||||
|
mut segment_visitor: impl FnMut(VtblSegment<'tcx>) -> ControlFlow<T>,
|
||||||
|
) -> Option<T> {
|
||||||
|
// The following constraints holds for the final arrangement.
|
||||||
|
// 1. The whole virtual table of the first direct super trait is included as the
|
||||||
|
// the prefix. If this trait doesn't have any super traits, then this step
|
||||||
|
// consists of the dsa metadata.
|
||||||
|
// 2. Then comes the proper pointer metadata(vptr) and all own methods for all
|
||||||
|
// other super traits except those already included as part of the first
|
||||||
|
// direct super trait virtual table.
|
||||||
|
// 3. finally, the own methods of this trait.
|
||||||
|
|
||||||
|
// This has the advantage that trait upcasting to the first direct super trait on each level
|
||||||
|
// is zero cost, and to another trait includes only replacing the pointer with one level indirection,
|
||||||
|
// while not using too much extra memory.
|
||||||
|
|
||||||
|
// For a single inheritance relationship like this,
|
||||||
|
// D --> C --> B --> A
|
||||||
|
// The resulting vtable will consists of these segments:
|
||||||
|
// DSA, A, B, C, D
|
||||||
|
|
||||||
|
// For a multiple inheritance relationship like this,
|
||||||
|
// D --> C --> A
|
||||||
|
// \-> B
|
||||||
|
// The resulting vtable will consists of these segments:
|
||||||
|
// DSA, A, B, B-vptr, C, D
|
||||||
|
|
||||||
|
// For a diamond inheritance relationship like this,
|
||||||
|
// D --> B --> A
|
||||||
|
// \-> C -/
|
||||||
|
// The resulting vtable will consists of these segments:
|
||||||
|
// DSA, A, B, C, C-vptr, D
|
||||||
|
|
||||||
|
// For a more complex inheritance relationship like this:
|
||||||
|
// O --> G --> C --> A
|
||||||
|
// \ \ \-> B
|
||||||
|
// | |-> F --> D
|
||||||
|
// | \-> E
|
||||||
|
// |-> N --> J --> H
|
||||||
|
// \ \-> I
|
||||||
|
// |-> M --> K
|
||||||
|
// \-> L
|
||||||
|
// The resulting vtable will consists of these segments:
|
||||||
|
// DSA, A, B, B-vptr, C, D, D-vptr, E, E-vptr, F, F-vptr, G,
|
||||||
|
// H, H-vptr, I, I-vptr, J, J-vptr, K, K-vptr, L, L-vptr, M, M-vptr,
|
||||||
|
// N, N-vptr, O
|
||||||
|
|
||||||
|
// emit dsa segment first.
|
||||||
|
if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::MetadataDSA) {
|
||||||
|
return Some(v);
|
||||||
|
}
|
||||||
|
|
||||||
|
let mut emit_vptr_on_new_entry = false;
|
||||||
|
let mut visited = PredicateSet::new(tcx);
|
||||||
|
let predicate = trait_ref.without_const().to_predicate(tcx);
|
||||||
|
let mut stack: SmallVec<[(ty::PolyTraitRef<'tcx>, _, _); 5]> =
|
||||||
|
smallvec![(trait_ref, emit_vptr_on_new_entry, None)];
|
||||||
|
visited.insert(predicate);
|
||||||
|
|
||||||
|
// the main traversal loop:
|
||||||
|
// basically we want to cut the inheritance directed graph into a few non-overlapping slices of nodes
|
||||||
|
// that each node is emitted after all its descendents have been emitted.
|
||||||
|
// so we convert the directed graph into a tree by skipping all previously visited nodes using a visited set.
|
||||||
|
// this is done on the fly.
|
||||||
|
// Each loop run emits a slice - it starts by find a "childless" unvisited node, backtracking upwards, and it
|
||||||
|
// stops after it finds a node that has a next-sibling node.
|
||||||
|
// This next-sibling node will used as the starting point of next slice.
|
||||||
|
|
||||||
|
// Example:
|
||||||
|
// For a diamond inheritance relationship like this,
|
||||||
|
// D#1 --> B#0 --> A#0
|
||||||
|
// \-> C#1 -/
|
||||||
|
|
||||||
|
// Starting point 0 stack [D]
|
||||||
|
// Loop run #0: Stack after diving in is [D B A], A is "childless"
|
||||||
|
// after this point, all newly visited nodes won't have a vtable that equals to a prefix of this one.
|
||||||
|
// Loop run #0: Emitting the slice [B A] (in reverse order), B has a next-sibling node, so this slice stops here.
|
||||||
|
// Loop run #0: Stack after exiting out is [D C], C is the next starting point.
|
||||||
|
// Loop run #1: Stack after diving in is [D C], C is "childless", since its child A is skipped(already emitted).
|
||||||
|
// Loop run #1: Emitting the slice [D C] (in reverse order). No one has a next-sibling node.
|
||||||
|
// Loop run #1: Stack after exiting out is []. Now the function exits.
|
||||||
|
|
||||||
|
loop {
|
||||||
|
// dive deeper into the stack, recording the path
|
||||||
|
'diving_in: loop {
|
||||||
|
if let Some((inner_most_trait_ref, _, _)) = stack.last() {
|
||||||
|
let inner_most_trait_ref = *inner_most_trait_ref;
|
||||||
|
let mut direct_super_traits_iter = tcx
|
||||||
|
.super_predicates_of(inner_most_trait_ref.def_id())
|
||||||
|
.predicates
|
||||||
|
.into_iter()
|
||||||
|
.filter_map(move |(pred, _)| {
|
||||||
|
pred.subst_supertrait(tcx, &inner_most_trait_ref).to_opt_poly_trait_pred()
|
||||||
|
});
|
||||||
|
|
||||||
|
'diving_in_skip_visited_traits: loop {
|
||||||
|
if let Some(next_super_trait) = direct_super_traits_iter.next() {
|
||||||
|
if visited.insert(next_super_trait.to_predicate(tcx)) {
|
||||||
|
// We're throwing away potential constness of super traits here.
|
||||||
|
// FIXME: handle ~const super traits
|
||||||
|
let next_super_trait = next_super_trait.map_bound(|t| t.trait_ref);
|
||||||
|
stack.push((
|
||||||
|
next_super_trait,
|
||||||
|
emit_vptr_on_new_entry,
|
||||||
|
Some(direct_super_traits_iter),
|
||||||
|
));
|
||||||
|
break 'diving_in_skip_visited_traits;
|
||||||
|
} else {
|
||||||
|
continue 'diving_in_skip_visited_traits;
|
||||||
|
}
|
||||||
|
} else {
|
||||||
|
break 'diving_in;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Other than the left-most path, vptr should be emitted for each trait.
|
||||||
|
emit_vptr_on_new_entry = true;
|
||||||
|
|
||||||
|
// emit innermost item, move to next sibling and stop there if possible, otherwise jump to outer level.
|
||||||
|
'exiting_out: loop {
|
||||||
|
if let Some((inner_most_trait_ref, emit_vptr, siblings_opt)) = stack.last_mut() {
|
||||||
|
if let ControlFlow::Break(v) = (segment_visitor)(VtblSegment::TraitOwnEntries {
|
||||||
|
trait_ref: *inner_most_trait_ref,
|
||||||
|
emit_vptr: *emit_vptr,
|
||||||
|
}) {
|
||||||
|
return Some(v);
|
||||||
|
}
|
||||||
|
|
||||||
|
'exiting_out_skip_visited_traits: loop {
|
||||||
|
if let Some(siblings) = siblings_opt {
|
||||||
|
if let Some(next_inner_most_trait_ref) = siblings.next() {
|
||||||
|
if visited.insert(next_inner_most_trait_ref.to_predicate(tcx)) {
|
||||||
|
// We're throwing away potential constness of super traits here.
|
||||||
|
// FIXME: handle ~const super traits
|
||||||
|
let next_inner_most_trait_ref =
|
||||||
|
next_inner_most_trait_ref.map_bound(|t| t.trait_ref);
|
||||||
|
*inner_most_trait_ref = next_inner_most_trait_ref;
|
||||||
|
*emit_vptr = emit_vptr_on_new_entry;
|
||||||
|
break 'exiting_out;
|
||||||
|
} else {
|
||||||
|
continue 'exiting_out_skip_visited_traits;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
stack.pop();
|
||||||
|
continue 'exiting_out;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
// all done
|
||||||
|
return None;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
fn dump_vtable_entries<'tcx>(
|
||||||
|
tcx: TyCtxt<'tcx>,
|
||||||
|
sp: Span,
|
||||||
|
trait_ref: ty::PolyTraitRef<'tcx>,
|
||||||
|
entries: &[VtblEntry<'tcx>],
|
||||||
|
) {
|
||||||
|
tcx.sess.emit_err(DumpVTableEntries {
|
||||||
|
span: sp,
|
||||||
|
trait_ref,
|
||||||
|
entries: format!("{:#?}", entries),
|
||||||
|
});
|
||||||
|
}
|
||||||
|
|
||||||
|
fn own_existential_vtable_entries<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId) -> &'tcx [DefId] {
|
||||||
|
let trait_methods = tcx
|
||||||
|
.associated_items(trait_def_id)
|
||||||
|
.in_definition_order()
|
||||||
|
.filter(|item| item.kind == ty::AssocKind::Fn);
|
||||||
|
// Now list each method's DefId (for within its trait).
|
||||||
|
let own_entries = trait_methods.filter_map(move |trait_method| {
|
||||||
|
debug!("own_existential_vtable_entry: trait_method={:?}", trait_method);
|
||||||
|
let def_id = trait_method.def_id;
|
||||||
|
|
||||||
|
// Some methods cannot be called on an object; skip those.
|
||||||
|
if !is_vtable_safe_method(tcx, trait_def_id, &trait_method) {
|
||||||
|
debug!("own_existential_vtable_entry: not vtable safe");
|
||||||
|
return None;
|
||||||
|
}
|
||||||
|
|
||||||
|
Some(def_id)
|
||||||
|
});
|
||||||
|
|
||||||
|
tcx.arena.alloc_from_iter(own_entries.into_iter())
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Given a trait `trait_ref`, iterates the vtable entries
|
||||||
|
/// that come from `trait_ref`, including its supertraits.
|
||||||
|
fn vtable_entries<'tcx>(
|
||||||
|
tcx: TyCtxt<'tcx>,
|
||||||
|
trait_ref: ty::PolyTraitRef<'tcx>,
|
||||||
|
) -> &'tcx [VtblEntry<'tcx>] {
|
||||||
|
debug!("vtable_entries({:?})", trait_ref);
|
||||||
|
|
||||||
|
let mut entries = vec![];
|
||||||
|
|
||||||
|
let vtable_segment_callback = |segment| -> ControlFlow<()> {
|
||||||
|
match segment {
|
||||||
|
VtblSegment::MetadataDSA => {
|
||||||
|
entries.extend(TyCtxt::COMMON_VTABLE_ENTRIES);
|
||||||
|
}
|
||||||
|
VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
|
||||||
|
let existential_trait_ref = trait_ref
|
||||||
|
.map_bound(|trait_ref| ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref));
|
||||||
|
|
||||||
|
// Lookup the shape of vtable for the trait.
|
||||||
|
let own_existential_entries =
|
||||||
|
tcx.own_existential_vtable_entries(existential_trait_ref.def_id());
|
||||||
|
|
||||||
|
let own_entries = own_existential_entries.iter().copied().map(|def_id| {
|
||||||
|
debug!("vtable_entries: trait_method={:?}", def_id);
|
||||||
|
|
||||||
|
// The method may have some early-bound lifetimes; add regions for those.
|
||||||
|
let substs = trait_ref.map_bound(|trait_ref| {
|
||||||
|
InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
|
||||||
|
GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
|
||||||
|
GenericParamDefKind::Type { .. }
|
||||||
|
| GenericParamDefKind::Const { .. } => {
|
||||||
|
trait_ref.substs[param.index as usize]
|
||||||
|
}
|
||||||
|
})
|
||||||
|
});
|
||||||
|
|
||||||
|
// The trait type may have higher-ranked lifetimes in it;
|
||||||
|
// erase them if they appear, so that we get the type
|
||||||
|
// at some particular call site.
|
||||||
|
let substs = tcx
|
||||||
|
.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), substs);
|
||||||
|
|
||||||
|
// It's possible that the method relies on where-clauses that
|
||||||
|
// do not hold for this particular set of type parameters.
|
||||||
|
// Note that this method could then never be called, so we
|
||||||
|
// do not want to try and codegen it, in that case (see #23435).
|
||||||
|
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
|
||||||
|
if impossible_predicates(tcx, predicates.predicates) {
|
||||||
|
debug!("vtable_entries: predicates do not hold");
|
||||||
|
return VtblEntry::Vacant;
|
||||||
|
}
|
||||||
|
|
||||||
|
let instance = ty::Instance::resolve_for_vtable(
|
||||||
|
tcx,
|
||||||
|
ty::ParamEnv::reveal_all(),
|
||||||
|
def_id,
|
||||||
|
substs,
|
||||||
|
)
|
||||||
|
.expect("resolution failed during building vtable representation");
|
||||||
|
VtblEntry::Method(instance)
|
||||||
|
});
|
||||||
|
|
||||||
|
entries.extend(own_entries);
|
||||||
|
|
||||||
|
if emit_vptr {
|
||||||
|
entries.push(VtblEntry::TraitVPtr(trait_ref));
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
ControlFlow::Continue(())
|
||||||
|
};
|
||||||
|
|
||||||
|
let _ = prepare_vtable_segments(tcx, trait_ref, vtable_segment_callback);
|
||||||
|
|
||||||
|
if tcx.has_attr(trait_ref.def_id(), sym::rustc_dump_vtable) {
|
||||||
|
let sp = tcx.def_span(trait_ref.def_id());
|
||||||
|
dump_vtable_entries(tcx, sp, trait_ref, &entries);
|
||||||
|
}
|
||||||
|
|
||||||
|
tcx.arena.alloc_from_iter(entries.into_iter())
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Find slot base for trait methods within vtable entries of another trait
|
||||||
|
pub(super) fn vtable_trait_first_method_offset<'tcx>(
|
||||||
|
tcx: TyCtxt<'tcx>,
|
||||||
|
key: (
|
||||||
|
ty::PolyTraitRef<'tcx>, // trait_to_be_found
|
||||||
|
ty::PolyTraitRef<'tcx>, // trait_owning_vtable
|
||||||
|
),
|
||||||
|
) -> usize {
|
||||||
|
let (trait_to_be_found, trait_owning_vtable) = key;
|
||||||
|
|
||||||
|
// #90177
|
||||||
|
let trait_to_be_found_erased = tcx.erase_regions(trait_to_be_found);
|
||||||
|
|
||||||
|
let vtable_segment_callback = {
|
||||||
|
let mut vtable_base = 0;
|
||||||
|
|
||||||
|
move |segment| {
|
||||||
|
match segment {
|
||||||
|
VtblSegment::MetadataDSA => {
|
||||||
|
vtable_base += 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);
|
||||||
|
}
|
||||||
|
vtable_base += count_own_vtable_entries(tcx, trait_ref);
|
||||||
|
if emit_vptr {
|
||||||
|
vtable_base += 1;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
ControlFlow::Continue(())
|
||||||
|
}
|
||||||
|
};
|
||||||
|
|
||||||
|
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");
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/// Find slot offset for trait vptr within vtable entries of another trait
|
||||||
|
pub(crate) fn vtable_trait_upcasting_coercion_new_vptr_slot<'tcx>(
|
||||||
|
tcx: TyCtxt<'tcx>,
|
||||||
|
key: (
|
||||||
|
Ty<'tcx>, // trait object type whose trait owning vtable
|
||||||
|
Ty<'tcx>, // trait object for supertrait
|
||||||
|
),
|
||||||
|
) -> Option<usize> {
|
||||||
|
let (source, target) = key;
|
||||||
|
assert!(matches!(&source.kind(), &ty::Dynamic(..)) && !source.needs_infer());
|
||||||
|
assert!(matches!(&target.kind(), &ty::Dynamic(..)) && !target.needs_infer());
|
||||||
|
|
||||||
|
// this has been typecked-before, so diagnostics is not really needed.
|
||||||
|
let unsize_trait_did = tcx.require_lang_item(LangItem::Unsize, None);
|
||||||
|
|
||||||
|
let trait_ref = tcx.mk_trait_ref(unsize_trait_did, [source, target]);
|
||||||
|
|
||||||
|
match tcx.codegen_select_candidate((ty::ParamEnv::reveal_all(), ty::Binder::dummy(trait_ref))) {
|
||||||
|
Ok(ImplSource::TraitUpcasting(implsrc_traitcasting)) => {
|
||||||
|
implsrc_traitcasting.vtable_vptr_slot
|
||||||
|
}
|
||||||
|
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()
|
||||||
|
}
|
||||||
|
|
||||||
|
pub(super) fn provide(providers: &mut ty::query::Providers) {
|
||||||
|
*providers = ty::query::Providers {
|
||||||
|
own_existential_vtable_entries,
|
||||||
|
vtable_entries,
|
||||||
|
vtable_trait_upcasting_coercion_new_vptr_slot,
|
||||||
|
..*providers
|
||||||
|
};
|
||||||
|
}
|
||||||
Loading…
Add table
Add a link
Reference in a new issue