diff options
| -rw-r--r-- | compiler/rustc_passes/src/dead.rs | 140 |
1 files changed, 50 insertions, 90 deletions
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs index e99bea57ff1..43d2361aad8 100644 --- a/compiler/rustc_passes/src/dead.rs +++ b/compiler/rustc_passes/src/dead.rs @@ -718,113 +718,81 @@ fn has_allow_dead_code_or_lang_attr( } } -// These check_* functions seeds items that -// 1) We want to explicitly consider as live: -// * Item annotated with #[allow(dead_code)] -// - This is done so that if we want to suppress warnings for a -// group of dead functions, we only have to annotate the "root". -// For example, if both `f` and `g` are dead and `f` calls `g`, -// then annotating `f` with `#[allow(dead_code)]` will suppress -// warning for both `f` and `g`. -// * Item annotated with #[lang=".."] -// - This is because lang items are always callable from elsewhere. -// or -// 2) We are not sure to be live or not -// * Implementations of traits and trait methods -fn check_item<'tcx>( +/// Examine the given definition and record it in the worklist if it should be considered live. +/// +/// We want to explicitly consider as live: +/// * Item annotated with #[allow(dead_code)] +/// This is done so that if we want to suppress warnings for a +/// group of dead functions, we only have to annotate the "root". +/// For example, if both `f` and `g` are dead and `f` calls `g`, +/// then annotating `f` with `#[allow(dead_code)]` will suppress +/// warning for both `f` and `g`. +/// +/// * Item annotated with #[lang=".."] +/// Lang items are always callable from elsewhere. +/// +/// For trait methods and implementations of traits, we are not certain that the definitions are +/// live at this stage. We record them in `unsolved_items` for later examination. +fn maybe_record_as_seed<'tcx>( tcx: TyCtxt<'tcx>, + owner_id: hir::OwnerId, worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>, unsolved_items: &mut Vec<LocalDefId>, - id: hir::ItemId, ) { - let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id); + let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, owner_id.def_id); if let Some(comes_from_allow) = allow_dead_code { - worklist.push((id.owner_id.def_id, comes_from_allow)); + worklist.push((owner_id.def_id, comes_from_allow)); } - match tcx.def_kind(id.owner_id) { + match tcx.def_kind(owner_id) { DefKind::Enum => { - let item = tcx.hir_item(id); - if let hir::ItemKind::Enum(_, _, ref enum_def) = item.kind { - if let Some(comes_from_allow) = allow_dead_code { - worklist.extend( - enum_def.variants.iter().map(|variant| (variant.def_id, comes_from_allow)), - ); + let adt = tcx.adt_def(owner_id); + if let Some(comes_from_allow) = allow_dead_code { + worklist.extend( + adt.variants() + .iter() + .map(|variant| (variant.def_id.expect_local(), comes_from_allow)), + ); + } + } + DefKind::AssocFn | DefKind::AssocConst | DefKind::AssocTy => { + if allow_dead_code.is_none() { + let parent = tcx.local_parent(owner_id.def_id); + match tcx.def_kind(parent) { + DefKind::Impl { of_trait: false } | DefKind::Trait => {} + DefKind::Impl { of_trait: true } => { + // We only care about associated items of traits, + // because they cannot be visited directly, + // so we later mark them as live if their corresponding traits + // or trait items and self types are both live, + // but inherent associated items can be visited and marked directly. + unsolved_items.push(owner_id.def_id); + } + _ => bug!(), } } } DefKind::Impl { of_trait } => { - if let Some(comes_from_allow) = - has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id) - { - worklist.push((id.owner_id.def_id, comes_from_allow)); - } else if of_trait { - unsolved_items.push(id.owner_id.def_id); - } - - for def_id in tcx.associated_item_def_ids(id.owner_id) { - let local_def_id = def_id.expect_local(); - - if let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, local_def_id) - { - worklist.push((local_def_id, comes_from_allow)); - } else if of_trait { - // We only care about associated items of traits, - // because they cannot be visited directly, - // so we later mark them as live if their corresponding traits - // or trait items and self types are both live, - // but inherent associated items can be visited and marked directly. - unsolved_items.push(local_def_id); - } + if allow_dead_code.is_none() && of_trait { + unsolved_items.push(owner_id.def_id); } } DefKind::GlobalAsm => { // global_asm! is always live. - worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No)); + worklist.push((owner_id.def_id, ComesFromAllowExpect::No)); } DefKind::Const => { - let item = tcx.hir_item(id); - if let hir::ItemKind::Const(ident, ..) = item.kind - && ident.name == kw::Underscore - { + if tcx.item_name(owner_id.def_id) == kw::Underscore { // `const _` is always live, as that syntax only exists for the side effects // of type checking and evaluating the constant expression, and marking them // as dead code would defeat that purpose. - worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No)); + worklist.push((owner_id.def_id, ComesFromAllowExpect::No)); } } _ => {} } } -fn check_trait_item( - tcx: TyCtxt<'_>, - worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>, - id: hir::TraitItemId, -) { - use hir::TraitItemKind::{Const, Fn, Type}; - - let trait_item = tcx.hir_trait_item(id); - if matches!(trait_item.kind, Const(_, Some(_)) | Type(_, Some(_)) | Fn(..)) - && let Some(comes_from_allow) = - has_allow_dead_code_or_lang_attr(tcx, trait_item.owner_id.def_id) - { - worklist.push((trait_item.owner_id.def_id, comes_from_allow)); - } -} - -fn check_foreign_item( - tcx: TyCtxt<'_>, - worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>, - id: hir::ForeignItemId, -) { - if matches!(tcx.def_kind(id.owner_id), DefKind::Static { .. } | DefKind::Fn) - && let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id) - { - worklist.push((id.owner_id.def_id, comes_from_allow)); - } -} - fn create_and_seed_worklist( tcx: TyCtxt<'_>, ) -> (Vec<(LocalDefId, ComesFromAllowExpect)>, Vec<LocalDefId>) { @@ -846,16 +814,8 @@ fn create_and_seed_worklist( .collect::<Vec<_>>(); let crate_items = tcx.hir_crate_items(()); - for id in crate_items.free_items() { - check_item(tcx, &mut worklist, &mut unsolved_impl_item, id); - } - - for id in crate_items.trait_items() { - check_trait_item(tcx, &mut worklist, id); - } - - for id in crate_items.foreign_items() { - check_foreign_item(tcx, &mut worklist, id); + for id in crate_items.owners() { + maybe_record_as_seed(tcx, id, &mut worklist, &mut unsolved_impl_item); } (worklist, unsolved_impl_item) |