Rollup of 20 pull requests

compiler/rustc_ast/src/ast.rs

@@ -407,7 +407,7 @@ impl GenericBound {
     }
 }
 
-pub type GenericBounds = Vec<GenericBound>;
+pub type GenericBounds = ThinVec<GenericBound>;
 
 /// Specifies the enforced ordering for generic parameters. In the future,
 /// if we wanted to relax this order, we could override `PartialEq` and
@@ -1534,7 +1534,7 @@ impl Expr {
                 let (Some(lhs), Some(rhs)) = (lhs.to_bound(), rhs.to_bound()) else {
                     return None;
                 };
-                TyKind::TraitObject(vec![lhs, rhs], TraitObjectSyntax::None)
+                TyKind::TraitObject(thin_vec![lhs, rhs], TraitObjectSyntax::None)
             }
 
             ExprKind::Underscore => TyKind::Infer,
@@ -1868,7 +1868,7 @@ pub enum ExprKind {
     ///
     /// Usually not written directly in user code but
     /// indirectly via the macro `core::mem::offset_of!(...)`.
-    OffsetOf(Box<Ty>, Vec<Ident>),
+    OffsetOf(Box<Ty>, ThinVec<Ident>),
 
     /// A macro invocation; pre-expansion.
     MacCall(Box<MacCall>),
@@ -4391,27 +4391,37 @@ mod size_asserts {
     // tidy-alphabetical-start
     static_assert_size!(AssocItem, 80);
     static_assert_size!(AssocItemKind, 16);
+    static_assert_size!(AttrKind, 16);
     static_assert_size!(Attribute, 32);
     static_assert_size!(Block, 32);
     static_assert_size!(Expr, 72);
     static_assert_size!(ExprKind, 40);
     static_assert_size!(Fn, 192);
+    static_assert_size!(FnDecl, 24);
+    static_assert_size!(FnHeader, 76);
+    static_assert_size!(FnSig, 96);
     static_assert_size!(ForeignItem, 80);
     static_assert_size!(ForeignItemKind, 16);
     static_assert_size!(GenericArg, 24);
+    static_assert_size!(GenericArgs, 40);
     static_assert_size!(GenericBound, 88);
+    static_assert_size!(GenericParam, 80);
     static_assert_size!(Generics, 40);
     static_assert_size!(Impl, 80);
     static_assert_size!(Item, 152);
     static_assert_size!(ItemKind, 88);
+    static_assert_size!(Lifetime, 16);
     static_assert_size!(LitKind, 24);
     static_assert_size!(Local, 96);
+    static_assert_size!(MetaItem, 88);
+    static_assert_size!(MetaItemKind, 40);
     static_assert_size!(MetaItemLit, 40);
     static_assert_size!(Param, 40);
     static_assert_size!(Pat, 80);
     static_assert_size!(PatKind, 56);
     static_assert_size!(Path, 24);
     static_assert_size!(PathSegment, 24);
+    static_assert_size!(QSelf, 24);
     static_assert_size!(Stmt, 32);
     static_assert_size!(StmtKind, 16);
     static_assert_size!(TraitImplHeader, 72);

compiler/rustc_ast/src/visit.rs

@@ -386,6 +386,8 @@ macro_rules! common_visitor_and_walkers {
         impl_visitable_list!(<$($lt)? $($mut)?>
             ThinVec<AngleBracketedArg>,
             ThinVec<Attribute>,
+            ThinVec<GenericBound>,
+            ThinVec<Ident>,
             ThinVec<(Ident, Option<Ident>)>,
             ThinVec<(NodeId, Path)>,
             ThinVec<PathSegment>,

compiler/rustc_attr_parsing/src/attributes/doc.rs

@@ -348,8 +348,11 @@ impl DocParser {
                 // If it's a list, then only `any()` and `none()` are allowed and they must not
                 // contain any item.
                 MetaItemOrLitParser::MetaItemParser(sub_item) => {
-                    if let Some(ident) = sub_item.ident()
-                        && [sym::any, sym::none].contains(&ident.name)
+                    let Some(ident) = sub_item.ident() else {
+                        cx.adcx().expected_identifier(sub_item.path().span());
+                        continue;
+                    };
+                    if [sym::any, sym::none].contains(&ident.name)
                         && let ArgParser::List(list) = sub_item.args()
                         && list.mixed().count() == 0
                     {
@@ -371,9 +374,7 @@ impl DocParser {
                     } else {
                         cx.emit_lint(
                             rustc_session::lint::builtin::INVALID_DOC_ATTRIBUTES,
-                            DocAutoCfgHideShowUnexpectedItem {
-                                attr_name: sub_item.ident().unwrap().name,
-                            },
+                            DocAutoCfgHideShowUnexpectedItem { attr_name: ident.name },
                             sub_item.span(),
                         );
                     }

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -167,7 +167,7 @@ fn show_substructure(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) ->
         let ty_dyn_debug = cx.ty(
             span,
             ast::TyKind::TraitObject(
-                vec![cx.trait_bound(path_debug, false)],
+                thin_vec![cx.trait_bound(path_debug, false)],
                 ast::TraitObjectSyntax::Dyn,
             ),
         );

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -617,7 +617,7 @@ impl<'a> TraitDef<'a> {
                     ident,
                     generics: Generics::default(),
                     after_where_clause: ast::WhereClause::default(),
-                    bounds: Vec::new(),
+                    bounds: ThinVec::new(),
                     ty: Some(type_def.to_ty(cx, self.span, type_ident, generics)),
                 })),
                 tokens: None,
@@ -639,7 +639,7 @@ impl<'a> TraitDef<'a> {
                     // Extra restrictions on the generics parameters to the
                     // type being derived upon.
                     let span = param.ident.span.with_ctxt(ctxt);
-                    let bounds: Vec<_> = self
+                    let bounds: ThinVec<_> = self
                         .additional_bounds
                         .iter()
                         .map(|p| {
@@ -723,7 +723,7 @@ impl<'a> TraitDef<'a> {
                     {
                         continue;
                     }
-                    let mut bounds: Vec<_> = self
+                    let mut bounds: ThinVec<_> = self
                         .additional_bounds
                         .iter()
                         .map(|p| {

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -22,7 +22,7 @@ use rustc_fs_util::{link_or_copy, path_to_c_string};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::{self, Lto, OutputType, Passes, SplitDwarfKind, SwitchWithOptPath};
-use rustc_span::{BytePos, InnerSpan, Pos, RemapPathScopeComponents, SpanData, SyntaxContext, sym};
+use rustc_span::{BytePos, InnerSpan, Pos, RemapPathScopeComponents, SpanData, SyntaxContext};
 use rustc_target::spec::{CodeModel, FloatAbi, RelocModel, SanitizerSet, SplitDebuginfo, TlsModel};
 use tracing::{debug, trace};
 
@@ -209,14 +209,8 @@ pub(crate) fn target_machine_factory(
 
     let code_model = to_llvm_code_model(sess.code_model());
 
-    let mut singlethread = sess.target.singlethread;
-
-    // On the wasm target once the `atomics` feature is enabled that means that
-    // we're no longer single-threaded, or otherwise we don't want LLVM to
-    // lower atomic operations to single-threaded operations.
-    if singlethread && sess.target.is_like_wasm && sess.target_features.contains(&sym::atomics) {
-        singlethread = false;
-    }
+    // This is used to set cfg_has_threads, so all logic must be in this method.
+    let singlethread = sess.target.singlethread(&sess.target_features);
 
     let triple = SmallCStr::new(&versioned_llvm_target(sess));
     let cpu = SmallCStr::new(llvm_util::target_cpu(sess));

compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -24,6 +24,7 @@ use rustc_target::spec::{CfgAbi, LlvmAbi, Os, RelocModel, Target, ef_avr_arch};
 use tracing::debug;
 
 use super::apple;
+use crate::errors;
 
 /// The default metadata loader. This is used by cg_llvm and cg_clif.
 ///
@@ -370,7 +371,7 @@ pub(super) fn elf_e_flags(architecture: Architecture, sess: &Session) -> u32 {
             if let Some(ref cpu) = sess.opts.cg.target_cpu {
                 ef_avr_arch(cpu)
             } else {
-                bug!("AVR CPU not explicitly specified")
+                sess.dcx().emit_fatal(errors::CpuRequired)
             }
         }
         Architecture::Csky => {

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -63,6 +63,17 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         result_place: Option<PlaceValue<Bx::Value>>,
         source_info: SourceInfo,
     ) -> IntrinsicResult<'tcx, Bx::Value> {
+        // When `-Zforce-intrinsic-fallback` is enabled, always use the fallback body if it exists,
+        if bx.tcx().sess.opts.unstable_opts.force_intrinsic_fallback
+            && let Some(def) = bx.tcx().intrinsic(instance.def_id())
+            && !def.must_be_overridden
+        {
+            return IntrinsicResult::Fallback(ty::Instance::new_raw(
+                instance.def_id(),
+                instance.args,
+            ));
+        }
+
         let span = source_info.span;
 
         let name = bx.tcx().item_name(instance.def_id());

compiler/rustc_data_structures/src/intern.rs

@@ -1,4 +1,3 @@
-use std::cmp::Ordering;
 use std::fmt::{self, Debug};
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
@@ -11,26 +10,40 @@ mod private {
     pub struct PrivateZst;
 }
 
-/// A reference to a value that is interned, and is known to be unique.
+/// This type is a reference with one special behaviour: the reference pointer (i.e. the address of
+/// the value referred to) is used for equality and hashing, rather than the value's contents, as
+/// would occur with a vanilla reference. There are two cases when this is useful.
 ///
-/// Note that it is possible to have a `T` and a `Interned<T>` that are (or
-/// refer to) equal but different values. But if you have two different
-/// `Interned<T>`s, they both refer to the same value, at a single location in
-/// memory. This means that equality and hashing can be done on the value's
-/// address rather than the value's contents, which can improve performance.
+/// - Types where uniqueness is guaranteed. This is most commonly achieved via interning -- hence
+///   the name `Interned` -- though it may also be possible via other means. In this case, the use
+///   of `Interned` is primarily a performance optimization, because pointer equality/hashing gives
+///   the same results as value equality/hashing, but is faster. (The use of the `Interned` type
+///   also provides documentation about the interned-ness.)
 ///
-/// The `PrivateZst` field means you can pattern match with `Interned(v, _)`
-/// but you can only construct a `Interned` with `new_unchecked`, and not
-/// directly.
+///   Note that in this case it is possible to have a `T` and a `Interned<T>` that are (or refer
+///   to) equal but different values. But if you have two different `Interned<T>`s, they both refer
+///   to the same value, at a single location in memory.
+///
+/// - Types with identity, where distinct values should always be considered unequal, even if they
+///   have equal values. These are rare in Rust, but do occur sometimes. In this case, the use of
+///   `Interned` gives different behaviour, because pointer equality/hashing gives different result
+///   to value equality/hashing, and is also faster.
+///
+/// The `PrivateZst` field means you can pattern match with `Interned(v, _)` but you can only
+/// construct a `Interned` with `new_unchecked`, and not directly. This means that all creation
+/// points can be audited easily.
 #[rustc_pass_by_value]
 pub struct Interned<'a, T>(pub &'a T, pub private::PrivateZst);
 
 impl<'a, T> Interned<'a, T> {
-    /// Create a new `Interned` value. The value referred to *must* be interned
-    /// and thus be unique, and it *must* remain unique in the future. This
-    /// function has `_unchecked` in the name but is not `unsafe`, because if
-    /// the uniqueness condition is violated condition it will cause incorrect
-    /// behaviour but will not affect memory safety.
+    /// Create a new `Interned` value. The value referred to *must* satisfy one of the following
+    /// two conditions.
+    /// - It must be unique and it must remain unique in the future.
+    /// - It must be of a type with "identity" such that distinct values should always be
+    ///   considered unequal.
+    ///
+    /// This function has `_unchecked` in the name but is not `unsafe`, because if neither of these
+    /// conditions is met it will cause incorrect behaviour but will not affect memory safety.
     #[inline]
     pub const fn new_unchecked(t: &'a T) -> Self {
         Interned(t, private::PrivateZst)
@@ -64,41 +77,10 @@ impl<'a, T> PartialEq for Interned<'a, T> {
 
 impl<'a, T> Eq for Interned<'a, T> {}
 
-impl<'a, T: PartialOrd> PartialOrd for Interned<'a, T> {
-    fn partial_cmp(&self, other: &Interned<'a, T>) -> Option<Ordering> {
-        // Pointer equality implies equality, due to the uniqueness constraint,
-        // but the contents must be compared otherwise.
-        if ptr::eq(self.0, other.0) {
-            Some(Ordering::Equal)
-        } else {
-            let res = self.0.partial_cmp(other.0);
-            debug_assert_ne!(res, Some(Ordering::Equal));
-            res
-        }
-    }
-}
-
-impl<'a, T: Ord> Ord for Interned<'a, T> {
-    fn cmp(&self, other: &Interned<'a, T>) -> Ordering {
-        // Pointer equality implies equality, due to the uniqueness constraint,
-        // but the contents must be compared otherwise.
-        if ptr::eq(self.0, other.0) {
-            Ordering::Equal
-        } else {
-            let res = self.0.cmp(other.0);
-            debug_assert_ne!(res, Ordering::Equal);
-            res
-        }
-    }
-}
-
-impl<'a, T> Hash for Interned<'a, T>
-where
-    T: Hash,
-{
+impl<'a, T> Hash for Interned<'a, T> {
     #[inline]
     fn hash<H: Hasher>(&self, s: &mut H) {
-        // Pointer hashing is sufficient, due to the uniqueness constraint.
+        // Pointer hashing is sufficient.
         ptr::hash(self.0, s)
     }
 }

compiler/rustc_data_structures/src/intern/tests.rs

@@ -1,5 +1,6 @@
 use super::*;
 
+#[allow(unused)]
 #[derive(Debug)]
 struct S(u32);
 
@@ -11,22 +12,6 @@ impl PartialEq for S {
 
 impl Eq for S {}
 
-impl PartialOrd for S {
-    fn partial_cmp(&self, other: &S) -> Option<Ordering> {
-        // The `==` case should be handled by `Interned`.
-        assert_ne!(self.0, other.0);
-        self.0.partial_cmp(&other.0)
-    }
-}
-
-impl Ord for S {
-    fn cmp(&self, other: &S) -> Ordering {
-        // The `==` case should be handled by `Interned`.
-        assert_ne!(self.0, other.0);
-        self.0.cmp(&other.0)
-    }
-}
-
 #[test]
 fn test_uniq() {
     let s1 = S(1);
@@ -45,14 +30,4 @@ fn test_uniq() {
     assert_eq!(v1, v1);
     assert_eq!(v3a, v3b);
     assert_ne!(v1, v4); // same content but different addresses: not equal
-
-    assert_eq!(v1.cmp(&v2), Ordering::Less);
-    assert_eq!(v3a.cmp(&v2), Ordering::Greater);
-    assert_eq!(v1.cmp(&v1), Ordering::Equal); // only uses Interned::eq, not S::cmp
-    assert_eq!(v3a.cmp(&v3b), Ordering::Equal); // only uses Interned::eq, not S::cmp
-
-    assert_eq!(v1.partial_cmp(&v2), Some(Ordering::Less));
-    assert_eq!(v3a.partial_cmp(&v2), Some(Ordering::Greater));
-    assert_eq!(v1.partial_cmp(&v1), Some(Ordering::Equal)); // only uses Interned::eq, not S::cmp
-    assert_eq!(v3a.partial_cmp(&v3b), Some(Ordering::Equal)); // only uses Interned::eq, not S::cmp
 }

compiler/rustc_feature/src/builtin_attrs.rs

@@ -50,6 +50,7 @@ const GATED_CFGS: &[GatedCfg] = &[
         sym::cfg_target_has_reliable_f16_f128,
         Features::cfg_target_has_reliable_f16_f128,
     ),
+    (sym::target_has_threads, sym::cfg_target_has_threads, Features::cfg_target_has_threads),
     (sym::target_object_format, sym::cfg_target_object_format, Features::cfg_target_object_format),
 ];
 

compiler/rustc_feature/src/unstable.rs

@@ -254,6 +254,8 @@ declare_features! (
     (unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
     /// Allows checking whether or not the backend correctly supports unstable float types.
     (internal, cfg_target_has_reliable_f16_f128, "1.88.0", None),
+    /// Allows checking whether or not the target might have thread support.
+    (internal, cfg_target_has_threads, "CURRENT_RUSTC_VERSION", None),
     /// Allows identifying the `compiler_builtins` crate.
     (internal, compiler_builtins, "1.13.0", None),
     /// Allows skipping `ConstParamTy_` trait implementation checks

compiler/rustc_monomorphize/src/collector.rs

@@ -995,11 +995,18 @@ fn visit_instance_use<'tcx>(
                 output.push(create_fn_mono_item(tcx, panic_instance, source));
             }
         } else if !intrinsic.must_be_overridden
-            && !tcx.sess.replaced_intrinsics.contains(&intrinsic.name)
+            && (tcx.sess.opts.unstable_opts.force_intrinsic_fallback
+                || !tcx.sess.replaced_intrinsics.contains(&intrinsic.name))
         {
             // Codegen the fallback body of intrinsics with fallback bodies.
             // We have to skip this otherwise as there's no body to codegen.
-            // We also skip intrinsics the backend handles, to reduce monomorphizations.
+            //
+            // We also skip `replaced_intrinsics` which are always replaced by the backend and hence
+            // monomorphizing the fallback body would be pointless.
+            //
+            // However, when -Zforce-intrinsic-fallback is set (e.g. to test the fallback
+            // implementations) we ignore the optimization hint and do monomorphize
+            // the fallback body.
             let instance = ty::Instance::new_raw(instance.def_id(), instance.args);
             if tcx.should_codegen_locally(instance) {
                 output.push(create_fn_mono_item(tcx, instance, source));

compiler/rustc_parse/src/parser/expr.rs

@@ -1154,8 +1154,8 @@ impl<'a> Parser<'a> {
     /// Parse the field access used in offset_of, matched by `$(e:expr)+`.
     /// Currently returns a list of idents. However, it should be possible in
     /// future to also do array indices, which might be arbitrary expressions.
-    pub(crate) fn parse_floating_field_access(&mut self) -> PResult<'a, Vec<Ident>> {
-        let mut fields = Vec::new();
+    pub(crate) fn parse_floating_field_access(&mut self) -> PResult<'a, ThinVec<Ident>> {
+        let mut fields = ThinVec::new();
         let mut trailing_dot = None;
 
         loop {