Auto merge of #129978 - matthiaskrgr:rollup-a7ryoox, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #101339 (enable -Zrandomize-layout in debug CI builds )
 - #120736 (rustdoc: add header map to the table of contents)
 - #127021 (Add target support for RTEMS Arm)
 - #128928 (CI: rfl: add more tools and steps)
 - #129584 (warn the user if the upstream master branch is old)
 - #129664 (Arbitrary self types v2: pointers feature gate.)
 - #129752 (Make supertrait and implied predicates queries defaulted)
 - #129918 (Update docs of `missing_abi` lint)
 - #129919 (Stabilize `waker_getters`)
 - #129925 (remove deprecated option `rust.split-debuginfo`)

Failed merges:

 - #129789 (rustdoc: use strategic boxing to shrink `clean::Item`)

r? `@ghost`
`@rustbot` modify labels: rollup

19 files changed, 167 insertions, 45 deletions

diff --git a/compiler/rustc/Cargo.toml b/compiler/rustc/Cargo.toml
index 5008069542f..a2fc9d5c408 100644
--- a/compiler/rustc/Cargo.toml
+++ b/compiler/rustc/Cargo.toml
@@ -30,5 +30,6 @@ features = ['unprefixed_malloc_on_supported_platforms']
 jemalloc = ['dep:jemalloc-sys']
 llvm = ['rustc_driver_impl/llvm']
 max_level_info = ['rustc_driver_impl/max_level_info']
+rustc_randomized_layouts = ['rustc_driver_impl/rustc_randomized_layouts']
 rustc_use_parallel_compiler = ['rustc_driver_impl/rustc_use_parallel_compiler']
 # tidy-alphabetical-end
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
index 5160b4ed0a2..7432768be4a 100644
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@@ -968,8 +968,8 @@ fn univariant<
     let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align };
     let mut max_repr_align = repr.align;
     let mut inverse_memory_index: IndexVec<u32, FieldIdx> = fields.indices().collect();
-    let optimize = !repr.inhibit_struct_field_reordering();
-    if optimize && fields.len() > 1 {
+    let optimize_field_order = !repr.inhibit_struct_field_reordering();
+    if optimize_field_order && fields.len() > 1 {
         let end = if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
         let optimizing = &mut inverse_memory_index.raw[..end];
         let fields_excluding_tail = &fields.raw[..end];
@@ -1176,7 +1176,7 @@ fn univariant<
     // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
     // Field 5 would be the first element, so memory_index is i:
     // Note: if we didn't optimize, it's already right.
-    let memory_index = if optimize {
+    let memory_index = if optimize_field_order {
         inverse_memory_index.invert_bijective_mapping()
     } else {
         debug_assert!(inverse_memory_index.iter().copied().eq(fields.indices()));
@@ -1189,6 +1189,9 @@ fn univariant<
     }
     let mut layout_of_single_non_zst_field = None;
     let mut abi = Abi::Aggregate { sized };
+
+    let optimize_abi = !repr.inhibit_newtype_abi_optimization();
+
     // Try to make this a Scalar/ScalarPair.
     if sized && size.bytes() > 0 {
         // We skip *all* ZST here and later check if we are good in terms of alignment.
@@ -1205,7 +1208,7 @@ fn univariant<
                     match field.abi {
                         // For plain scalars, or vectors of them, we can't unpack
                         // newtypes for `#[repr(C)]`, as that affects C ABIs.
-                        Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
+                        Abi::Scalar(_) | Abi::Vector { .. } if optimize_abi => {
                             abi = field.abi;
                         }
                         // But scalar pairs are Rust-specific and get
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index df29b3d54f0..be42bc84932 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -43,14 +43,17 @@ bitflags! {
         const IS_SIMD            = 1 << 1;
         const IS_TRANSPARENT     = 1 << 2;
         // Internal only for now. If true, don't reorder fields.
+        // On its own it does not prevent ABI optimizations.
         const IS_LINEAR          = 1 << 3;
-        // If true, the type's layout can be randomized using
-        // the seed stored in `ReprOptions.field_shuffle_seed`
+        // If true, the type's crate has opted into layout randomization.
+        // Other flags can still inhibit reordering and thus randomization.
+        // The seed stored in `ReprOptions.field_shuffle_seed`.
         const RANDOMIZE_LAYOUT   = 1 << 4;
         // Any of these flags being set prevent field reordering optimisation.
-        const IS_UNOPTIMISABLE   = ReprFlags::IS_C.bits()
+        const FIELD_ORDER_UNOPTIMIZABLE   = ReprFlags::IS_C.bits()
                                  | ReprFlags::IS_SIMD.bits()
                                  | ReprFlags::IS_LINEAR.bits();
+        const ABI_UNOPTIMIZABLE = ReprFlags::IS_C.bits() | ReprFlags::IS_SIMD.bits();
     }
 }
 
@@ -139,10 +142,14 @@ impl ReprOptions {
         self.c() || self.int.is_some()
     }
 
+    pub fn inhibit_newtype_abi_optimization(&self) -> bool {
+        self.flags.intersects(ReprFlags::ABI_UNOPTIMIZABLE)
+    }
+
     /// Returns `true` if this `#[repr()]` guarantees a fixed field order,
     /// e.g. `repr(C)` or `repr(<int>)`.
     pub fn inhibit_struct_field_reordering(&self) -> bool {
-        self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
+        self.flags.intersects(ReprFlags::FIELD_ORDER_UNOPTIMIZABLE) || self.int.is_some()
     }
 
     /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index 91cbffcd707..6d6d3f35a4b 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -23,6 +23,7 @@ rustc_hir_analysis = { path = "../rustc_hir_analysis" }
 rustc_hir_pretty = { path = "../rustc_hir_pretty" }
 rustc_hir_typeck = { path = "../rustc_hir_typeck" }
 rustc_incremental = { path = "../rustc_incremental" }
+rustc_index = { path = "../rustc_index" }
 rustc_infer = { path = "../rustc_infer" }
 rustc_interface = { path = "../rustc_interface" }
 rustc_lint = { path = "../rustc_lint" }
@@ -72,6 +73,10 @@ ctrlc = "3.4.4"
 # tidy-alphabetical-start
 llvm = ['rustc_interface/llvm']
 max_level_info = ['rustc_log/max_level_info']
+rustc_randomized_layouts = [
+    'rustc_index/rustc_randomized_layouts',
+    'rustc_middle/rustc_randomized_layouts'
+]
 rustc_use_parallel_compiler = [
     'rustc_data_structures/rustc_use_parallel_compiler',
     'rustc_interface/rustc_use_parallel_compiler',
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index cd6adbda039..fba65883550 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -349,8 +349,10 @@ declare_features! (
     (unstable, adt_const_params, "1.56.0", Some(95174)),
     /// Allows defining an `#[alloc_error_handler]`.
     (unstable, alloc_error_handler, "1.29.0", Some(51540)),
-    /// Allows trait methods with arbitrary self types.
+    /// Allows inherent and trait methods with arbitrary self types.
     (unstable, arbitrary_self_types, "1.23.0", Some(44874)),
+    /// Allows inherent and trait methods with arbitrary self types that are raw pointers.
+    (unstable, arbitrary_self_types_pointers, "CURRENT_RUSTC_VERSION", Some(44874)),
     /// Enables experimental inline assembly support for additional architectures.
     (unstable, asm_experimental_arch, "1.58.0", Some(93335)),
     /// Allows using `label` operands in inline assembly.
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index f83eac7cd6c..3627faf8dfc 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1652,6 +1652,13 @@ fn check_fn_or_method<'tcx>(
     }
 }
 
+/// The `arbitrary_self_types_pointers` feature implies `arbitrary_self_types`.
+#[derive(Clone, Copy, PartialEq)]
+enum ArbitrarySelfTypesLevel {
+    Basic,        // just arbitrary_self_types
+    WithPointers, // both arbitrary_self_types and arbitrary_self_types_pointers
+}
+
 #[instrument(level = "debug", skip(wfcx))]
 fn check_method_receiver<'tcx>(
     wfcx: &WfCheckingCtxt<'_, 'tcx>,
@@ -1684,14 +1691,27 @@ fn check_method_receiver<'tcx>(
         return Ok(());
     }
 
-    if tcx.features().arbitrary_self_types {
-        if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
-            // Report error; `arbitrary_self_types` was enabled.
-            return Err(tcx.dcx().emit_err(errors::InvalidReceiverTy { span, receiver_ty }));
-        }
+    let arbitrary_self_types_level = if tcx.features().arbitrary_self_types_pointers {
+        Some(ArbitrarySelfTypesLevel::WithPointers)
+    } else if tcx.features().arbitrary_self_types {
+        Some(ArbitrarySelfTypesLevel::Basic)
     } else {
-        if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, false) {
-            return Err(if receiver_is_valid(wfcx, span, receiver_ty, self_ty, true) {
+        None
+    };
+
+    if !receiver_is_valid(wfcx, span, receiver_ty, self_ty, arbitrary_self_types_level) {
+        return Err(match arbitrary_self_types_level {
+            // Wherever possible, emit a message advising folks that the features
+            // `arbitrary_self_types` or `arbitrary_self_types_pointers` might
+            // have helped.
+            None if receiver_is_valid(
+                wfcx,
+                span,
+                receiver_ty,
+                self_ty,
+                Some(ArbitrarySelfTypesLevel::Basic),
+            ) =>
+            {
                 // Report error; would have worked with `arbitrary_self_types`.
                 feature_err(
                     &tcx.sess,
@@ -1699,25 +1719,49 @@ fn check_method_receiver<'tcx>(
                     span,
                     format!(
                         "`{receiver_ty}` cannot be used as the type of `self` without \
-                         the `arbitrary_self_types` feature",
+                            the `arbitrary_self_types` feature",
                     ),
                 )
                 .with_help(fluent::hir_analysis_invalid_receiver_ty_help)
                 .emit()
-            } else {
-                // Report error; would not have worked with `arbitrary_self_types`.
+            }
+            None | Some(ArbitrarySelfTypesLevel::Basic)
+                if receiver_is_valid(
+                    wfcx,
+                    span,
+                    receiver_ty,
+                    self_ty,
+                    Some(ArbitrarySelfTypesLevel::WithPointers),
+                ) =>
+            {
+                // Report error; would have worked with `arbitrary_self_types_pointers`.
+                feature_err(
+                    &tcx.sess,
+                    sym::arbitrary_self_types_pointers,
+                    span,
+                    format!(
+                        "`{receiver_ty}` cannot be used as the type of `self` without \
+                            the `arbitrary_self_types_pointers` feature",
+                    ),
+                )
+                .with_help(fluent::hir_analysis_invalid_receiver_ty_help)
+                .emit()
+            }
+            _ =>
+            // Report error; would not have worked with `arbitrary_self_types[_pointers]`.
+            {
                 tcx.dcx().emit_err(errors::InvalidReceiverTy { span, receiver_ty })
-            });
-        }
+            }
+        });
     }
     Ok(())
 }
 
 /// Returns whether `receiver_ty` would be considered a valid receiver type for `self_ty`. If
 /// `arbitrary_self_types` is enabled, `receiver_ty` must transitively deref to `self_ty`, possibly
-/// through a `*const/mut T` raw pointer. If the feature is not enabled, the requirements are more
-/// strict: `receiver_ty` must implement `Receiver` and directly implement
-/// `Deref<Target = self_ty>`.
+/// through a `*const/mut T` raw pointer if  `arbitrary_self_types_pointers` is also enabled.
+/// If neither feature is enabled, the requirements are more strict: `receiver_ty` must implement
+/// `Receiver` and directly implement `Deref<Target = self_ty>`.
 ///
 /// N.B., there are cases this function returns `true` but causes an error to be emitted,
 /// particularly when `receiver_ty` derefs to a type that is the same as `self_ty` but has the
@@ -1727,7 +1771,7 @@ fn receiver_is_valid<'tcx>(
     span: Span,
     receiver_ty: Ty<'tcx>,
     self_ty: Ty<'tcx>,
-    arbitrary_self_types_enabled: bool,
+    arbitrary_self_types_enabled: Option<ArbitrarySelfTypesLevel>,
 ) -> bool {
     let infcx = wfcx.infcx;
     let tcx = wfcx.tcx();
@@ -1745,8 +1789,8 @@ fn receiver_is_valid<'tcx>(
 
     let mut autoderef = Autoderef::new(infcx, wfcx.param_env, wfcx.body_def_id, span, receiver_ty);
 
-    // The `arbitrary_self_types` feature allows raw pointer receivers like `self: *const Self`.
-    if arbitrary_self_types_enabled {
+    // The `arbitrary_self_types_pointers` feature allows raw pointer receivers like `self: *const Self`.
+    if arbitrary_self_types_enabled == Some(ArbitrarySelfTypesLevel::WithPointers) {
         autoderef = autoderef.include_raw_pointers();
     }
 
@@ -1772,7 +1816,7 @@ fn receiver_is_valid<'tcx>(
 
         // Without `feature(arbitrary_self_types)`, we require that each step in the
         // deref chain implement `receiver`.
-        if !arbitrary_self_types_enabled {
+        if arbitrary_self_types_enabled.is_none() {
             if !receiver_is_implemented(
                 wfcx,
                 receiver_trait_def_id,
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 0cf5403b3c0..2fdba8446bd 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -403,7 +403,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     mode,
                 }));
             } else if bad_ty.reached_raw_pointer
-                && !self.tcx.features().arbitrary_self_types
+                && !self.tcx.features().arbitrary_self_types_pointers
                 && !self.tcx.sess.at_least_rust_2018()
             {
                 // this case used to be allowed by the compiler,
diff --git a/compiler/rustc_index/Cargo.toml b/compiler/rustc_index/Cargo.toml
index 92ea3f278dc..f7d18f84e34 100644
--- a/compiler/rustc_index/Cargo.toml
+++ b/compiler/rustc_index/Cargo.toml
@@ -20,4 +20,5 @@ nightly = [
     "dep:rustc_macros",
     "rustc_index_macros/nightly",
 ]
+rustc_randomized_layouts = []
 # tidy-alphabetical-end
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index f773b5b46ad..52f354b8eca 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -33,8 +33,19 @@ pub use vec::IndexVec;
 ///
 /// </div>
 #[macro_export]
+#[cfg(not(feature = "rustc_randomized_layouts"))]
 macro_rules! static_assert_size {
     ($ty:ty, $size:expr) => {
         const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
     };
 }
+
+#[macro_export]
+#[cfg(feature = "rustc_randomized_layouts")]
+macro_rules! static_assert_size {
+    ($ty:ty, $size:expr) => {
+        // no effect other than using the statements.
+        // struct sizes are not deterministic under randomized layouts
+        const _: (usize, usize) = ($size, ::std::mem::size_of::<$ty>());
+    };
+}
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 7063f488209..25d33126754 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -3706,7 +3706,7 @@ declare_lint_pass!(UnusedDocComment => [UNUSED_DOC_COMMENTS]);
 
 declare_lint! {
     /// The `missing_abi` lint detects cases where the ABI is omitted from
-    /// extern declarations.
+    /// `extern` declarations.
     ///
     /// ### Example
     ///
@@ -3720,10 +3720,12 @@ declare_lint! {
     ///
     /// ### Explanation
     ///
-    /// Historically, Rust implicitly selected C as the ABI for extern
-    /// declarations. We expect to add new ABIs, like `C-unwind`, in the future,
-    /// though this has not yet happened, and especially with their addition
-    /// seeing the ABI easily will make code review easier.
+    /// For historic reasons, Rust implicitly selects `C` as the default ABI for
+    /// `extern` declarations. [Other ABIs] like `C-unwind` and `system` have
+    /// been added since then, and especially with their addition seeing the ABI
+    /// easily makes code review easier.
+    ///
+    /// [Other ABIs]: https://doc.rust-lang.org/reference/items/external-blocks.html#abi
     pub MISSING_ABI,
     Allow,
     "No declared ABI for extern declaration"
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 1264510a831..53da07aeaa6 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -247,8 +247,8 @@ provide! { tcx, def_id, other, cdata,
     explicit_predicates_of => { table }
     generics_of => { table }
     inferred_outlives_of => { table_defaulted_array }
-    explicit_super_predicates_of => { table }
-    explicit_implied_predicates_of => { table }
+    explicit_super_predicates_of => { table_defaulted_array }
+    explicit_implied_predicates_of => { table_defaulted_array }
     type_of => { table }
     type_alias_is_lazy => { table_direct }
     variances_of => { table }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 88256c4db04..c55583b39a6 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1443,9 +1443,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             if let DefKind::Trait = def_kind {
                 record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
-                record_array!(self.tables.explicit_super_predicates_of[def_id] <-
+                record_defaulted_array!(self.tables.explicit_super_predicates_of[def_id] <-
                     self.tcx.explicit_super_predicates_of(def_id).skip_binder());
-                record_array!(self.tables.explicit_implied_predicates_of[def_id] <-
+                record_defaulted_array!(self.tables.explicit_implied_predicates_of[def_id] <-
                     self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
 
                 let module_children = self.tcx.module_children_local(local_id);
@@ -1454,9 +1454,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             if let DefKind::TraitAlias = def_kind {
                 record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
-                record_array!(self.tables.explicit_super_predicates_of[def_id] <-
+                record_defaulted_array!(self.tables.explicit_super_predicates_of[def_id] <-
                     self.tcx.explicit_super_predicates_of(def_id).skip_binder());
-                record_array!(self.tables.explicit_implied_predicates_of[def_id] <-
+                record_defaulted_array!(self.tables.explicit_implied_predicates_of[def_id] <-
                     self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
             }
             if let DefKind::Trait | DefKind::Impl { .. } = def_kind {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index a84923130c3..8180a507a51 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -390,6 +390,8 @@ define_tables! {
     explicit_item_bounds: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     explicit_item_super_predicates: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     inferred_outlives_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
+    explicit_super_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
+    explicit_implied_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     inherent_impls: Table<DefIndex, LazyArray<DefIndex>>,
     associated_types_for_impl_traits_in_associated_fn: Table<DefIndex, LazyArray<DefId>>,
     associated_type_for_effects: Table<DefIndex, Option<LazyValue<DefId>>>,
@@ -419,10 +421,6 @@ define_tables! {
     lookup_deprecation_entry: Table<DefIndex, LazyValue<attr::Deprecation>>,
     explicit_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
     generics_of: Table<DefIndex, LazyValue<ty::Generics>>,
-    explicit_super_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
-    // As an optimization, we only store this for trait aliases,
-    // since it's identical to explicit_super_predicates_of for traits.
-    explicit_implied_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     type_of: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, Ty<'static>>>>,
     variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
     fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, ty::PolyFnSig<'static>>>>,
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index 69e3b703cce..b23589afb58 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -40,5 +40,6 @@ tracing = "0.1"
 
 [features]
 # tidy-alphabetical-start
+rustc_randomized_layouts = []
 rustc_use_parallel_compiler = ["dep:rustc-rayon-core"]
 # tidy-alphabetical-end
diff --git a/compiler/rustc_middle/src/query/plumbing.rs b/compiler/rustc_middle/src/query/plumbing.rs
index c9bd702cce3..0320a91d142 100644
--- a/compiler/rustc_middle/src/query/plumbing.rs
+++ b/compiler/rustc_middle/src/query/plumbing.rs
@@ -337,6 +337,7 @@ macro_rules! define_callbacks {
                 // Ensure that values grow no larger than 64 bytes by accident.
                 // Increase this limit if necessary, but do try to keep the size low if possible
                 #[cfg(target_pointer_width = "64")]
+                #[cfg(not(feature = "rustc_randomized_layouts"))]
                 const _: () = {
                     if mem::size_of::<Value<'static>>() > 64 {
                         panic!("{}", concat!(
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index cd94c0afad0..ee70a6346d9 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -35,6 +35,7 @@ use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
 use rustc_errors::{Diag, ErrorGuaranteed, StashKey};
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
+use rustc_hir::LangItem;
 use rustc_index::IndexVec;
 use rustc_macros::{
     extension, Decodable, Encodable, HashStable, TyDecodable, TyEncodable, TypeFoldable,
@@ -1570,8 +1571,15 @@ impl<'tcx> TyCtxt<'tcx> {
             flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
         }
 
+        // box is special, on the one hand the compiler assumes an ordered layout, with the pointer
+        // always at offset zero. On the other hand we want scalar abi optimizations.
+        let is_box = self.is_lang_item(did.to_def_id(), LangItem::OwnedBox);
+
         // This is here instead of layout because the choice must make it into metadata.
-        if !self.consider_optimizing(|| format!("Reorder fields of {:?}", self.def_path_str(did))) {
+        if is_box
+            || !self
+                .consider_optimizing(|| format!("Reorder fields of {:?}", self.def_path_str(did)))
+        {
             flags.insert(ReprFlags::IS_LINEAR);
         }
 
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 34765209605..36b31d10c4d 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -407,6 +407,7 @@ symbols! {
         append_const_msg,
         arbitrary_enum_discriminant,
         arbitrary_self_types,
+        arbitrary_self_types_pointers,
         args,
         arith_offset,
         arm,
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index e6b00c84254..6abd8a0d6b7 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1695,6 +1695,8 @@ supported_targets! {
     ("armv7r-none-eabihf", armv7r_none_eabihf),
     ("armv8r-none-eabihf", armv8r_none_eabihf),
 
+    ("armv7-rtems-eabihf", armv7_rtems_eabihf),
+
     ("x86_64-pc-solaris", x86_64_pc_solaris),
     ("sparcv9-sun-solaris", sparcv9_sun_solaris),
 
diff --git a/compiler/rustc_target/src/spec/targets/armv7_rtems_eabihf.rs b/compiler/rustc_target/src/spec/targets/armv7_rtems_eabihf.rs
new file mode 100644
index 00000000000..1edecac095f
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/armv7_rtems_eabihf.rs
@@ -0,0 +1,35 @@
+use crate::spec::{cvs, Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, Target, TargetOptions};
+
+pub(crate) fn target() -> Target {
+    Target {
+        llvm_target: "armv7-unknown-none-eabihf".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("Armv7 RTEMS (Requires RTEMS toolchain and kernel".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
+        arch: "arm".into(),
+
+        options: TargetOptions {
+            os: "rtems".into(),
+            families: cvs!["unix"],
+            abi: "eabihf".into(),
+            linker_flavor: LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+            linker: None,
+            relocation_model: RelocModel::Static,
+            panic_strategy: PanicStrategy::Abort,
+            features: "+thumb2,+neon,+vfp3".into(),
+            max_atomic_width: Some(64),
+            emit_debug_gdb_scripts: false,
+            // GCC defaults to 8 for arm-none here.
+            c_enum_min_bits: Some(8),
+            eh_frame_header: false,
+            no_default_libraries: false,
+            env: "newlib".into(),
+            ..Default::default()
+        },
+    }
+}