Rip out rustc_layout_scalar_valid_range_* attribute support

compiler/rustc_abi/src/layout.rs

@@ -1,6 +1,6 @@
 use std::collections::BTreeSet;
 use std::fmt::{self, Write};
-use std::ops::{Bound, Deref};
+use std::ops::Deref;
 use std::{cmp, iter};
 
 use rustc_hashes::Hash64;
@@ -348,7 +348,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         variants: &IndexSlice<VariantIdx, IndexVec<FieldIdx, F>>,
         is_enum: bool,
         is_special_no_niche: bool,
-        scalar_valid_range: (Bound<u128>, Bound<u128>),
         discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool),
         discriminants: impl Iterator<Item = (VariantIdx, i128)>,
         always_sized: bool,
@@ -380,7 +379,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 variants,
                 is_enum,
                 is_special_no_niche,
-                scalar_valid_range,
                 always_sized,
                 present_first,
             )
@@ -530,7 +528,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         variants: &IndexSlice<VariantIdx, IndexVec<FieldIdx, F>>,
         is_enum: bool,
         is_special_no_niche: bool,
-        scalar_valid_range: (Bound<u128>, Bound<u128>),
         always_sized: bool,
         present_first: VariantIdx,
     ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
@@ -570,52 +567,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             return Ok(st);
         }
 
-        let (start, end) = scalar_valid_range;
-        match st.backend_repr {
-            BackendRepr::Scalar(ref mut scalar) | BackendRepr::ScalarPair(ref mut scalar, _) => {
-                // Enlarging validity ranges would result in missed
-                // optimizations, *not* wrongly assuming the inner
-                // value is valid. e.g. unions already enlarge validity ranges,
-                // because the values may be uninitialized.
-                //
-                // Because of that we only check that the start and end
-                // of the range is representable with this scalar type.
-
-                let max_value = scalar.size(dl).unsigned_int_max();
-                if let Bound::Included(start) = start {
-                    // FIXME(eddyb) this might be incorrect - it doesn't
-                    // account for wrap-around (end < start) ranges.
-                    assert!(start <= max_value, "{start} > {max_value}");
-                    scalar.valid_range_mut().start = start;
-                }
-                if let Bound::Included(end) = end {
-                    // FIXME(eddyb) this might be incorrect - it doesn't
-                    // account for wrap-around (end < start) ranges.
-                    assert!(end <= max_value, "{end} > {max_value}");
-                    scalar.valid_range_mut().end = end;
-                }
-
-                // Update `largest_niche` if we have introduced a larger niche.
-                let niche = Niche::from_scalar(dl, Size::ZERO, *scalar);
-                if let Some(niche) = niche {
-                    match st.largest_niche {
-                        Some(largest_niche) => {
-                            // Replace the existing niche even if they're equal,
-                            // because this one is at a lower offset.
-                            if largest_niche.available(dl) <= niche.available(dl) {
-                                st.largest_niche = Some(niche);
-                            }
-                        }
-                        None => st.largest_niche = Some(niche),
-                    }
-                }
-            }
-            _ => assert!(
-                start == Bound::Unbounded && end == Bound::Unbounded,
-                "nonscalar layout for layout_scalar_valid_range type: {st:#?}",
-            ),
-        }
-
         Ok(st)
     }
 

compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs

@@ -92,32 +92,6 @@ impl NoArgsAttributeParser for RustcNoImplicitAutorefsParser {
     const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcNoImplicitAutorefs;
 }
 
-pub(crate) struct RustcLayoutScalarValidRangeStartParser;
-
-impl SingleAttributeParser for RustcLayoutScalarValidRangeStartParser {
-    const PATH: &[Symbol] = &[sym::rustc_layout_scalar_valid_range_start];
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Struct)]);
-    const TEMPLATE: AttributeTemplate = template!(List: &["start"]);
-
-    fn convert(cx: &mut AcceptContext<'_, '_>, args: &ArgParser) -> Option<AttributeKind> {
-        parse_single_integer(cx, args)
-            .map(|n| AttributeKind::RustcLayoutScalarValidRangeStart(Box::new(n), cx.attr_span))
-    }
-}
-
-pub(crate) struct RustcLayoutScalarValidRangeEndParser;
-
-impl SingleAttributeParser for RustcLayoutScalarValidRangeEndParser {
-    const PATH: &[Symbol] = &[sym::rustc_layout_scalar_valid_range_end];
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Struct)]);
-    const TEMPLATE: AttributeTemplate = template!(List: &["end"]);
-
-    fn convert(cx: &mut AcceptContext<'_, '_>, args: &ArgParser) -> Option<AttributeKind> {
-        parse_single_integer(cx, args)
-            .map(|n| AttributeKind::RustcLayoutScalarValidRangeEnd(Box::new(n), cx.attr_span))
-    }
-}
-
 pub(crate) struct RustcLegacyConstGenericsParser;
 
 impl SingleAttributeParser for RustcLegacyConstGenericsParser {

compiler/rustc_attr_parsing/src/attributes/util.rs

@@ -33,7 +33,7 @@ pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
 /// Parse a single integer.
 ///
 /// Used by attributes that take a single integer as argument, such as
-/// `#[link_ordinal]` and `#[rustc_layout_scalar_valid_range_start]`.
+/// `#[link_ordinal]`.
 /// `cx` is the context given to the attribute.
 /// `args` is the parser for the attribute arguments.
 pub(crate) fn parse_single_integer(

compiler/rustc_attr_parsing/src/context.rs

@@ -208,8 +208,6 @@ attribute_parsers!(
         Single<RustcDumpSymbolNameParser>,
         Single<RustcForceInlineParser>,
         Single<RustcIfThisChangedParser>,
-        Single<RustcLayoutScalarValidRangeEndParser>,
-        Single<RustcLayoutScalarValidRangeStartParser>,
         Single<RustcLegacyConstGenericsParser>,
         Single<RustcLintOptDenyFieldAccessParser>,
         Single<RustcMacroTransparencyParser>,

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -1442,7 +1442,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
                 // First check that the base type is valid
                 self.visit_value(&val.transmute(self.ecx.layout_of(*base)?, self.ecx)?)?;
                 // When you extend this match, make sure to also add tests to
-                // tests/ui/type/pattern_types/validity.rs((
+                // tests/ui/type/pattern_types/validity.rs
                 match **pat {
                     // Range and non-null patterns are precisely reflected into `valid_range` and thus
                     // handled fully by `visit_scalar` (called below).
@@ -1457,6 +1457,34 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
                     // we won't see optimizations actually breaking such programs.
                     ty::PatternKind::Or(_patterns) => {}
                 }
+                // FIXME(pattern_types): handle everything based on the pattern, not on the layout.
+                // it's ok to run scalar validation even if the pattern type is `u8 is 0..=255` and thus
+                // allows uninit values, because that's rare and so not a perf issue.
+                match val.layout.backend_repr {
+                    BackendRepr::Scalar(scalar_layout) => {
+                        if !scalar_layout.is_uninit_valid() {
+                            // There is something to check here.
+                            // We read directly via `ecx` since the read cannot fail -- we already read
+                            // this field above when recursing into the field.
+                            let scalar = self.ecx.read_scalar(val)?;
+                            self.visit_scalar(scalar, scalar_layout)?;
+                        }
+                    }
+                    BackendRepr::ScalarPair(a_layout, b_layout) => {
+                        // We can only proceed if *both* scalars need to be initialized.
+                        // FIXME: find a way to also check ScalarPair when one side can be uninit but
+                        // the other must be init.
+                        if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
+                            // We read directly via `ecx` since the read cannot fail -- we already read
+                            // this field above when recursing into the field.
+                            let (a, b) = self.ecx.read_immediate(val)?.to_scalar_pair();
+                            self.visit_scalar(a, a_layout)?;
+                            self.visit_scalar(b, b_layout)?;
+                        }
+                    }
+                    BackendRepr::SimdVector { .. } | BackendRepr::SimdScalableVector { .. } => unreachable!(),
+                    BackendRepr::Memory { .. } => unreachable!()
+                }
             }
             ty::Adt(adt, _) if adt.is_maybe_dangling() => {
                 let old_may_dangle = mem::replace(&mut self.may_dangle, true);
@@ -1479,51 +1507,55 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
             }
         }
 
-        // *After* all of this, check further information stored in the layout. We need to check
-        // this to handle types like `NonNull` where the `Scalar` info is more restrictive than what
-        // the fields say (`rustc_layout_scalar_valid_range_start`). But in most cases, this will
-        // just propagate what the fields say, and then we want the error to point at the field --
-        // so, we first recurse, then we do this check.
+        // *After* all of this, check further information stored in the layout.
+        // On leaf types like `!` or empty enums, this will raise the error.
+        // This means that for types wrapping such a type, we won't ever get here, but it's
+        // just the simplest way to check for this case.
         //
         // FIXME: We could avoid some redundant checks here. For newtypes wrapping
         // scalars, we do the same check on every "level" (e.g., first we check
-        // MyNewtype and then the scalar in there).
+        // the fields of MyNewtype, and then we check MyNewType again).
         if val.layout.is_uninhabited() {
             let ty = val.layout.ty;
             throw_validation_failure!(
                 self.path,
                 format!("encountered a value of uninhabited type `{ty}`")
             );
         }
-        match val.layout.backend_repr {
-            BackendRepr::Scalar(scalar_layout) => {
-                if !scalar_layout.is_uninit_valid() {
-                    // There is something to check here.
-                    // We read directly via `ecx` since the read cannot fail -- we already read
-                    // this field above when recursing into the field.
-                    let scalar = self.ecx.read_scalar(val)?;
-                    self.visit_scalar(scalar, scalar_layout)?;
+        if cfg!(debug_assertions) {
+            // Check that we don't miss any new changes to layout computation in our checks above.
+            match val.layout.backend_repr {
+                BackendRepr::Scalar(scalar_layout) => {
+                    if !scalar_layout.is_uninit_valid() {
+                        // There is something to check here.
+                        // We read directly via `ecx` since the read cannot fail -- we already read
+                        // this field above when recursing into the field.
+                        let scalar = self
+                            .ecx
+                            .read_scalar(val)
+                            .expect("the above checks should have fully handled this situation");
+                        self.visit_scalar(scalar, scalar_layout)
+                            .expect("the above checks should have fully handled this situation");
+                    }
                 }
-            }
-            BackendRepr::ScalarPair(a_layout, b_layout) => {
-                // We can only proceed if *both* scalars need to be initialized.
-                // FIXME: find a way to also check ScalarPair when one side can be uninit but
-                // the other must be init.
-                if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
-                    // We read directly via `ecx` since the read cannot fail -- we already read
-                    // this field above when recursing into the field.
-                    let (a, b) = self.ecx.read_immediate(val)?.to_scalar_pair();
-                    self.visit_scalar(a, a_layout)?;
-                    self.visit_scalar(b, b_layout)?;
+                BackendRepr::ScalarPair(a_layout, b_layout) => {
+                    // We can only proceed if *both* scalars need to be initialized.
+                    // FIXME: find a way to also check ScalarPair when one side can be uninit but
+                    // the other must be init.
+                    if !a_layout.is_uninit_valid() && !b_layout.is_uninit_valid() {
+                        let (a, b) = self
+                            .ecx
+                            .read_immediate(val)
+                            .expect("the above checks should have fully handled this situation")
+                            .to_scalar_pair();
+                        self.visit_scalar(a, a_layout)
+                            .expect("the above checks should have fully handled this situation");
+                        self.visit_scalar(b, b_layout)
+                            .expect("the above checks should have fully handled this situation");
+                    }
                 }
-            }
-            BackendRepr::SimdVector { .. } | BackendRepr::SimdScalableVector { .. } => {
-                // No checks here, we assume layout computation gets this right.
-                // (This is harder to check since Miri does not represent these as `Immediate`. We
-                // also cannot use field projections since this might be a newtype around a vector.)
-            }
-            BackendRepr::Memory { .. } => {
-                // Nothing to do.
+                BackendRepr::SimdVector { .. } | BackendRepr::SimdScalableVector { .. } => {}
+                BackendRepr::Memory { .. } => {}
             }
         }
 

compiler/rustc_feature/src/builtin_attrs.rs

@@ -573,16 +573,6 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     // Internal attributes, Layout related:
     // ==========================================================================
 
-    rustc_attr!(
-        rustc_layout_scalar_valid_range_start,
-        "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
-        niche optimizations in the standard library",
-    ),
-    rustc_attr!(
-        rustc_layout_scalar_valid_range_end,
-        "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
-        niche optimizations in the standard library",
-    ),
     rustc_attr!(
         rustc_simd_monomorphize_lane_limit,
         "the `#[rustc_simd_monomorphize_lane_limit]` attribute is just used by std::simd \

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -1435,12 +1435,6 @@ pub enum AttributeKind {
     /// Represents `#[rustc_intrinsic_const_stable_indirect]`
     RustcIntrinsicConstStableIndirect,
 
-    /// Represents `#[rustc_layout_scalar_valid_range_end]`.
-    RustcLayoutScalarValidRangeEnd(Box<u128>, Span),
-
-    /// Represents `#[rustc_layout_scalar_valid_range_start]`.
-    RustcLayoutScalarValidRangeStart(Box<u128>, Span),
-
     /// Represents `#[rustc_legacy_const_generics]`
     RustcLegacyConstGenerics {
         fn_indexes: ThinVec<(usize, Span)>,

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -147,8 +147,6 @@ impl AttributeKind {
             RustcInsignificantDtor => Yes,
             RustcIntrinsic => Yes,
             RustcIntrinsicConstStableIndirect => No,
-            RustcLayoutScalarValidRangeEnd(..) => Yes,
-            RustcLayoutScalarValidRangeStart(..) => Yes,
             RustcLegacyConstGenerics { .. } => Yes,
             RustcLintOptDenyFieldAccess { .. } => Yes,
             RustcLintOptTy => Yes,

compiler/rustc_hir_analysis/src/collect.rs

@@ -15,7 +15,7 @@
 //! crate as a kind of pass. This should eventually be factored away.
 
 use std::cell::Cell;
-use std::ops::{Bound, ControlFlow};
+use std::ops::ControlFlow;
 use std::{assert_matches, iter};
 
 use rustc_abi::{ExternAbi, Size};
@@ -1039,12 +1039,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
                 .fields()
                 .iter()
                 .map(|f| tcx.type_of(f.def_id).instantiate_identity().skip_norm_wip());
-            // constructors for structs with `layout_scalar_valid_range` are unsafe to call
-            let safety = match tcx.layout_scalar_valid_range(adt_def_id) {
-                (Bound::Unbounded, Bound::Unbounded) => hir::Safety::Safe,
-                _ => hir::Safety::Unsafe,
-            };
-            ty::Binder::dummy(tcx.mk_fn_sig_rust_abi(inputs, ty, safety))
+            ty::Binder::dummy(tcx.mk_fn_sig_rust_abi(inputs, ty, hir::Safety::Safe))
         }
 
         Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {

compiler/rustc_middle/src/ty/context.rs

@@ -11,7 +11,7 @@ use std::env::VarError;
 use std::ffi::OsStr;
 use std::hash::{Hash, Hasher};
 use std::marker::{PhantomData, PointeeSized};
-use std::ops::{Bound, Deref};
+use std::ops::Deref;
 use std::sync::{Arc, OnceLock};
 use std::{fmt, iter, mem};
 
@@ -947,17 +947,6 @@ impl<'tcx> TyCtxt<'tcx> {
         matches!(self.as_lang_item(def_id), Some(LangItem::Sized | LangItem::MetaSized))
     }
 
-    /// Returns a range of the start/end indices specified with the
-    /// `rustc_layout_scalar_valid_range` attribute.
-    // FIXME(eddyb) this is an awkward spot for this method, maybe move it?
-    pub fn layout_scalar_valid_range(self, def_id: DefId) -> (Bound<u128>, Bound<u128>) {
-        let start = find_attr!(self, def_id, RustcLayoutScalarValidRangeStart(n, _) => Bound::Included(**n)).unwrap_or(Bound::Unbounded);
-        let end =
-            find_attr!(self, def_id, RustcLayoutScalarValidRangeEnd(n, _) => Bound::Included(**n))
-                .unwrap_or(Bound::Unbounded);
-        (start, end)
-    }
-
     pub fn lift<T: Lift<TyCtxt<'tcx>>>(self, value: T) -> Option<T::Lifted> {
         value.lift_to_interner(self)
     }

compiler/rustc_middle/src/ty/layout.rs

@@ -1,4 +1,3 @@
-use std::ops::Bound;
 use std::{cmp, fmt};
 
 use rustc_abi as abi;
@@ -465,17 +464,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 // Newtype.
                 if def.variants().len() == 1 {
                     if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
-                        return Ok(SizeSkeleton::Pointer {
-                            non_zero: non_zero
-                                || match tcx.layout_scalar_valid_range(def.did()) {
-                                    (Bound::Included(start), Bound::Unbounded) => start > 0,
-                                    (Bound::Included(start), Bound::Included(end)) => {
-                                        0 < start && start < end
-                                    }
-                                    _ => false,
-                                },
-                            tail,
-                        });
+                        return Ok(SizeSkeleton::Pointer { non_zero, tail });
                     } else {
                         return Err(err);
                     }

compiler/rustc_mir_build/src/builder/mod.rs

@@ -1276,5 +1276,3 @@ mod expr;
 mod matches;
 mod misc;
 mod scope;
-
-pub(crate) use expr::category::Category as ExprCategory;