Merge pull request #4417 from rust-lang/rustup-2025-06-28

Automatic Rustup

15 files changed, 105 insertions, 61 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/call.rs b/compiler/rustc_const_eval/src/interpret/call.rs
index 37677f9e048..79c14b204e3 100644
--- a/compiler/rustc_const_eval/src/interpret/call.rs
+++ b/compiler/rustc_const_eval/src/interpret/call.rs
@@ -6,7 +6,7 @@ use std::borrow::Cow;
 use either::{Left, Right};
 use rustc_abi::{self as abi, ExternAbi, FieldIdx, Integer, VariantIdx};
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::layout::{FnAbiOf, IntegerExt, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{FnAbiOf, IntegerExt, TyAndLayout};
 use rustc_middle::ty::{self, AdtDef, Instance, Ty, VariantDef};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::sym;
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index 9e15f4572d7..1036935bb10 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -6,7 +6,7 @@ use rustc_apfloat::{Float, FloatConvert};
 use rustc_middle::mir::CastKind;
 use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar};
 use rustc_middle::ty::adjustment::PointerCoercion;
-use rustc_middle::ty::layout::{IntegerExt, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{IntegerExt, TyAndLayout};
 use rustc_middle::ty::{self, FloatTy, Ty};
 use rustc_middle::{bug, span_bug};
 use tracing::trace;
diff --git a/compiler/rustc_const_eval/src/interpret/discriminant.rs b/compiler/rustc_const_eval/src/interpret/discriminant.rs
index 6c4b000e16b..b7e7f65c95c 100644
--- a/compiler/rustc_const_eval/src/interpret/discriminant.rs
+++ b/compiler/rustc_const_eval/src/interpret/discriminant.rs
@@ -1,7 +1,7 @@
 //! Functions for reading and writing discriminants of multi-variant layouts (enums and coroutines).
 
 use rustc_abi::{self as abi, FieldIdx, TagEncoding, VariantIdx, Variants};
-use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout};
+use rustc_middle::ty::layout::{PrimitiveExt, TyAndLayout};
 use rustc_middle::ty::{self, CoroutineArgsExt, ScalarInt, Ty};
 use rustc_middle::{mir, span_bug};
 use tracing::{instrument, trace};
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index b69bc0918be..46c784b41c6 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -7,7 +7,8 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::mir::interpret::{ErrorHandled, InvalidMetaKind, ReportedErrorInfo};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{
-    self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOfHelpers, TyAndLayout,
+    self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
+    TyAndLayout,
 };
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypingEnv, Variance};
 use rustc_middle::{mir, span_bug};
@@ -21,7 +22,7 @@ use super::{
     MemPlaceMeta, Memory, OpTy, Place, PlaceTy, PointerArithmetic, Projectable, Provenance,
     err_inval, interp_ok, throw_inval, throw_ub, throw_ub_custom,
 };
-use crate::{ReportErrorExt, fluent_generated as fluent, util};
+use crate::{ReportErrorExt, enter_trace_span, fluent_generated as fluent, util};
 
 pub struct InterpCx<'tcx, M: Machine<'tcx>> {
     /// Stores the `Machine` instance.
@@ -91,6 +92,20 @@ impl<'tcx, M: Machine<'tcx>> LayoutOfHelpers<'tcx> for InterpCx<'tcx, M> {
     }
 }
 
+impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
+    /// This inherent method takes priority over the trait method with the same name in LayoutOf,
+    /// and allows wrapping the actual [LayoutOf::layout_of] with a tracing span.
+    /// See [LayoutOf::layout_of] for the original documentation.
+    #[inline]
+    pub fn layout_of(
+        &self,
+        ty: Ty<'tcx>,
+    ) -> <InterpCx<'tcx, M> as LayoutOfHelpers<'tcx>>::LayoutOfResult {
+        let _span = enter_trace_span!(M, "InterpCx::layout_of", "ty = {:?}", ty.kind());
+        LayoutOf::layout_of(self, ty)
+    }
+}
+
 impl<'tcx, M: Machine<'tcx>> FnAbiOfHelpers<'tcx> for InterpCx<'tcx, M> {
     type FnAbiOfResult = Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, InterpErrorKind<'tcx>>;
 
@@ -284,6 +299,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         frame: &Frame<'tcx, M::Provenance, M::FrameExtra>,
         value: T,
     ) -> Result<T, ErrorHandled> {
+        let _span = enter_trace_span!(
+            M,
+            "instantiate_from_frame_and_normalize_erasing_regions",
+            "{}",
+            frame.instance
+        );
         frame
             .instance
             .try_instantiate_mir_and_normalize_erasing_regions(
@@ -362,7 +383,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     /// Returns the actual dynamic size and alignment of the place at the given type.
     /// Only the "meta" (metadata) part of the place matters.
     /// This can fail to provide an answer for extern types.
-    pub(super) fn size_and_align_of(
+    pub(super) fn size_and_align_from_meta(
         &self,
         metadata: &MemPlaceMeta<M::Provenance>,
         layout: &TyAndLayout<'tcx>,
@@ -388,7 +409,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 // adjust alignment and size for them?
                 let field = layout.field(self, layout.fields.count() - 1);
                 let Some((unsized_size, mut unsized_align)) =
-                    self.size_and_align_of(metadata, &field)?
+                    self.size_and_align_from_meta(metadata, &field)?
                 else {
                     // A field with an extern type. We don't know the actual dynamic size
                     // or the alignment.
@@ -450,11 +471,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         }
     }
     #[inline]
-    pub fn size_and_align_of_mplace(
+    pub fn size_and_align_of_val(
         &self,
-        mplace: &MPlaceTy<'tcx, M::Provenance>,
+        val: &impl Projectable<'tcx, M::Provenance>,
     ) -> InterpResult<'tcx, Option<(Size, Align)>> {
-        self.size_and_align_of(&mplace.meta(), &mplace.layout)
+        self.size_and_align_from_meta(&val.meta(), &val.layout())
     }
 
     /// Jump to the given block.
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index 96c39c7bb32..b29c5c7c7d7 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -8,7 +8,7 @@ use rustc_abi::Size;
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic};
-use rustc_middle::ty::layout::{LayoutOf as _, TyAndLayout, ValidityRequirement};
+use rustc_middle::ty::layout::{TyAndLayout, ValidityRequirement};
 use rustc_middle::ty::{GenericArgsRef, Ty, TyCtxt};
 use rustc_middle::{bug, ty};
 use rustc_span::{Symbol, sym};
@@ -125,7 +125,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 // dereferenceable!
                 let place = self.ref_to_mplace(&self.read_immediate(&args[0])?)?;
                 let (size, align) = self
-                    .size_and_align_of_mplace(&place)?
+                    .size_and_align_of_val(&place)?
                     .ok_or_else(|| err_unsup_format!("`extern type` does not have known layout"))?;
 
                 let result = match intrinsic_name {
diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs
index b9e022c9604..d6d230fbd17 100644
--- a/compiler/rustc_const_eval/src/interpret/machine.rs
+++ b/compiler/rustc_const_eval/src/interpret/machine.rs
@@ -443,7 +443,11 @@ pub trait Machine<'tcx>: Sized {
     ///
     /// Used to prevent statics from self-initializing by reading from their own memory
     /// as it is being initialized.
-    fn before_alloc_read(_ecx: &InterpCx<'tcx, Self>, _alloc_id: AllocId) -> InterpResult<'tcx> {
+    fn before_alloc_access(
+        _tcx: TyCtxtAt<'tcx>,
+        _machine: &Self,
+        _alloc_id: AllocId,
+    ) -> InterpResult<'tcx> {
         interp_ok(())
     }
 
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index 99a4bc1b7d6..69fceb02ff9 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -720,7 +720,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // do this after `check_and_deref_ptr` to ensure some basic sanity has already been checked.
         if !self.memory.validation_in_progress.get() {
             if let Ok((alloc_id, ..)) = self.ptr_try_get_alloc_id(ptr, size_i64) {
-                M::before_alloc_read(self, alloc_id)?;
+                M::before_alloc_access(self.tcx, &self.machine, alloc_id)?;
             }
         }
 
@@ -821,6 +821,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         if let Some((alloc_id, offset, prov, alloc, machine)) = ptr_and_alloc {
             let range = alloc_range(offset, size);
             if !validation_in_progress {
+                // For writes, it's okay to only call those when there actually is a non-zero
+                // amount of bytes to be written: a zero-sized write doesn't manifest anything.
+                M::before_alloc_access(tcx, machine, alloc_id)?;
                 M::before_memory_write(
                     tcx,
                     machine,
@@ -877,12 +880,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         if let Some(fn_val) = self.get_fn_alloc(id) {
             let align = match fn_val {
                 FnVal::Instance(instance) => {
-                    // Function alignment can be set globally with the `-Zmin-function-alignment=<n>` flag;
-                    // the alignment from a `#[repr(align(<n>))]` is used if it specifies a higher alignment.
-                    let fn_align = self.tcx.codegen_fn_attrs(instance.def_id()).alignment;
-                    let global_align = self.tcx.sess.opts.unstable_opts.min_function_alignment;
-
-                    Ord::max(global_align, fn_align).unwrap_or(Align::ONE)
+                    self.tcx.codegen_fn_attrs(instance.def_id()).alignment.unwrap_or(Align::ONE)
                 }
                 // Machine-specific extra functions currently do not support alignment restrictions.
                 FnVal::Other(_) => Align::ONE,
@@ -1401,6 +1399,14 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let src_parts = self.get_ptr_access(src, size)?;
         let dest_parts = self.get_ptr_access(dest, size * num_copies)?; // `Size` multiplication
 
+        // Similar to `get_ptr_alloc`, we need to call `before_alloc_access` even for zero-sized
+        // reads. However, just like in `get_ptr_alloc_mut`, the write part is okay to skip for
+        // zero-sized writes.
+        if let Ok((alloc_id, ..)) = self.ptr_try_get_alloc_id(src, size.bytes().try_into().unwrap())
+        {
+            M::before_alloc_access(tcx, &self.machine, alloc_id)?;
+        }
+
         // FIXME: we look up both allocations twice here, once before for the `check_ptr_access`
         // and once below to get the underlying `&[mut] Allocation`.
 
@@ -1412,6 +1418,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let src_alloc = self.get_alloc_raw(src_alloc_id)?;
         let src_range = alloc_range(src_offset, size);
         assert!(!self.memory.validation_in_progress.get(), "we can't be copying during validation");
+
+        // Trigger read hook.
         // For the overlapping case, it is crucial that we trigger the read hook
         // before the write hook -- the aliasing model cares about the order.
         M::before_memory_read(
@@ -1438,16 +1446,18 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let provenance = src_alloc
             .provenance()
             .prepare_copy(src_range, dest_offset, num_copies, self)
-            .map_err(|e| e.to_interp_error(dest_alloc_id))?;
+            .map_err(|e| e.to_interp_error(src_alloc_id))?;
         // Prepare a copy of the initialization mask.
         let init = src_alloc.init_mask().prepare_copy(src_range);
 
-        // Destination alloc preparations and access hooks.
-        let (dest_alloc, extra) = self.get_alloc_raw_mut(dest_alloc_id)?;
+        // Destination alloc preparations...
+        let (dest_alloc, machine) = self.get_alloc_raw_mut(dest_alloc_id)?;
         let dest_range = alloc_range(dest_offset, size * num_copies);
+        // ...and access hooks.
+        M::before_alloc_access(tcx, machine, dest_alloc_id)?;
         M::before_memory_write(
             tcx,
-            extra,
+            machine,
             &mut dest_alloc.extra,
             dest,
             (dest_alloc_id, dest_prov),
diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs
index 77667ba823a..62cbbae24a8 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -8,7 +8,7 @@ use rustc_abi as abi;
 use rustc_abi::{BackendRepr, HasDataLayout, Size};
 use rustc_hir::def::Namespace;
 use rustc_middle::mir::interpret::ScalarSizeMismatch;
-use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, TyAndLayout};
 use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter};
 use rustc_middle::ty::{ConstInt, ScalarInt, Ty, TyCtxt};
 use rustc_middle::{bug, mir, span_bug, ty};
@@ -878,9 +878,9 @@ mod size_asserts {
 
     use super::*;
     // tidy-alphabetical-start
-    static_assert_size!(Immediate, 48);
     static_assert_size!(ImmTy<'_>, 64);
-    static_assert_size!(Operand, 56);
+    static_assert_size!(Immediate, 48);
     static_assert_size!(OpTy<'_>, 72);
+    static_assert_size!(Operand, 56);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index 899670aeb62..74f8a0a7b09 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -3,7 +3,7 @@ use rustc_abi::Size;
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_middle::mir::NullOp;
 use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar};
-use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{self, FloatTy, ScalarInt, Ty};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::sym;
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index f5d3de7b1b2..3028568dd8f 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -7,7 +7,7 @@ use std::assert_matches::assert_matches;
 use either::{Either, Left, Right};
 use rustc_abi::{BackendRepr, HasDataLayout, Size};
 use rustc_middle::ty::Ty;
-use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{bug, mir, span_bug};
 use tracing::{instrument, trace};
 
@@ -470,7 +470,7 @@ where
     ) -> InterpResult<'tcx, Option<AllocRef<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
     {
         let (size, _align) = self
-            .size_and_align_of_mplace(mplace)?
+            .size_and_align_of_val(mplace)?
             .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
         // We check alignment separately, and *after* checking everything else.
         // If an access is both OOB and misaligned, we want to see the bounds error.
@@ -486,7 +486,7 @@ where
     ) -> InterpResult<'tcx, Option<AllocRefMut<'_, 'tcx, M::Provenance, M::AllocExtra, M::Bytes>>>
     {
         let (size, _align) = self
-            .size_and_align_of_mplace(mplace)?
+            .size_and_align_of_val(mplace)?
             .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
         // We check alignment separately, and raise that error *after* checking everything else.
         // If an access is both OOB and misaligned, we want to see the bounds error.
@@ -888,11 +888,11 @@ where
         trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout().ty);
 
         let dest = dest.force_mplace(self)?;
-        let Some((dest_size, _)) = self.size_and_align_of_mplace(&dest)? else {
+        let Some((dest_size, _)) = self.size_and_align_of_val(&dest)? else {
             span_bug!(self.cur_span(), "copy_op needs (dynamically) sized values")
         };
         if cfg!(debug_assertions) {
-            let src_size = self.size_and_align_of_mplace(&src)?.unwrap().0;
+            let src_size = self.size_and_align_of_val(&src)?.unwrap().0;
             assert_eq!(src_size, dest_size, "Cannot copy differently-sized data");
         } else {
             // As a cheap approximation, we compare the fixed parts of the size.
@@ -980,7 +980,7 @@ where
         kind: MemoryKind<M::MemoryKind>,
         meta: MemPlaceMeta<M::Provenance>,
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
-        let Some((size, align)) = self.size_and_align_of(&meta, &layout)? else {
+        let Some((size, align)) = self.size_and_align_from_meta(&meta, &layout)? else {
             span_bug!(self.cur_span(), "cannot allocate space for `extern` type, size is not known")
         };
         let ptr = self.allocate_ptr(size, align, kind, AllocInit::Uninit)?;
@@ -1056,9 +1056,9 @@ mod size_asserts {
 
     use super::*;
     // tidy-alphabetical-start
+    static_assert_size!(MPlaceTy<'_>, 64);
     static_assert_size!(MemPlace, 48);
     static_assert_size!(MemPlaceMeta, 24);
-    static_assert_size!(MPlaceTy<'_>, 64);
     static_assert_size!(Place, 48);
     static_assert_size!(PlaceTy<'_>, 64);
     // tidy-alphabetical-end
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index ad47a19a14d..306697d4ec9 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -12,7 +12,7 @@ use std::ops::Range;
 
 use rustc_abi::{self as abi, FieldIdx, Size, VariantIdx};
 use rustc_middle::ty::Ty;
-use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{bug, mir, span_bug, ty};
 use tracing::{debug, instrument};
 
@@ -168,7 +168,7 @@ where
             // Re-use parent metadata to determine dynamic field layout.
             // With custom DSTS, this *will* execute user-defined code, but the same
             // happens at run-time so that's okay.
-            match self.size_and_align_of(&base_meta, &field_layout)? {
+            match self.size_and_align_from_meta(&base_meta, &field_layout)? {
                 Some((_, align)) => {
                     // For packed types, we need to cap alignment.
                     let align = if let ty::Adt(def, _) = base.layout().ty.kind()
diff --git a/compiler/rustc_const_eval/src/interpret/stack.rs b/compiler/rustc_const_eval/src/interpret/stack.rs
index 2a2d1bb2754..3361a586b8e 100644
--- a/compiler/rustc_const_eval/src/interpret/stack.rs
+++ b/compiler/rustc_const_eval/src/interpret/stack.rs
@@ -7,7 +7,7 @@ use either::{Either, Left, Right};
 use rustc_hir as hir;
 use rustc_hir::definitions::DefPathData;
 use rustc_index::IndexVec;
-use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{bug, mir};
 use rustc_mir_dataflow::impls::always_storage_live_locals;
diff --git a/compiler/rustc_const_eval/src/interpret/traits.rs b/compiler/rustc_const_eval/src/interpret/traits.rs
index 7249ef23bf6..8b634955bb7 100644
--- a/compiler/rustc_const_eval/src/interpret/traits.rs
+++ b/compiler/rustc_const_eval/src/interpret/traits.rs
@@ -1,6 +1,5 @@
 use rustc_abi::{Align, FieldIdx, Size};
 use rustc_middle::mir::interpret::{InterpResult, Pointer};
-use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, ExistentialPredicateStableCmpExt, Ty, TyCtxt, VtblEntry};
 use tracing::trace;
 
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 7d76d925ef2..998ef3729ea 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -24,7 +24,7 @@ use rustc_middle::mir::interpret::{
     ExpectedKind, InterpErrorKind, InvalidMetaKind, Misalignment, PointerKind, Provenance,
     UnsupportedOpInfo, ValidationErrorInfo, alloc_range, interp_ok,
 };
-use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutCx, TyAndLayout};
 use rustc_middle::ty::{self, Ty};
 use rustc_span::{Symbol, sym};
 use tracing::trace;
@@ -35,6 +35,7 @@ use super::{
     Machine, MemPlaceMeta, PlaceTy, Pointer, Projectable, Scalar, ValueVisitor, err_ub,
     format_interp_error,
 };
+use crate::enter_trace_span;
 
 // for the validation errors
 #[rustfmt::skip]
@@ -493,7 +494,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         }
         // Make sure this is dereferenceable and all.
         let size_and_align = try_validation!(
-            self.ecx.size_and_align_of_mplace(&place),
+            self.ecx.size_and_align_of_val(&place),
             self.path,
             Ub(InvalidMeta(msg)) => match msg {
                 InvalidMetaKind::SliceTooBig => InvalidMetaSliceTooLarge { ptr_kind },
@@ -570,6 +571,8 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                     };
                     let (size, _align) =
                         global_alloc.size_and_align(*self.ecx.tcx, self.ecx.typing_env);
+                    let alloc_actual_mutbl =
+                        global_alloc.mutability(*self.ecx.tcx, self.ecx.typing_env);
 
                     if let GlobalAlloc::Static(did) = global_alloc {
                         let DefKind::Static { nested, .. } = self.ecx.tcx.def_kind(did) else {
@@ -597,9 +600,11 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                                 skip_recursive_check = !nested;
                             }
                             CtfeValidationMode::Const { .. } => {
-                                // We can't recursively validate `extern static`, so we better reject them.
-                                if self.ecx.tcx.is_foreign_item(did) {
-                                    throw_validation_failure!(self.path, ConstRefToExtern);
+                                // If this is mutable memory or an `extern static`, there's no point in checking it -- we'd
+                                // just get errors trying to read the value.
+                                if alloc_actual_mutbl.is_mut() || self.ecx.tcx.is_foreign_item(did)
+                                {
+                                    skip_recursive_check = true;
                                 }
                             }
                         }
@@ -618,9 +623,6 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                                 mutbl
                             }
                         };
-                        // Determine what it actually points to.
-                        let alloc_actual_mutbl =
-                            global_alloc.mutability(*self.ecx.tcx, self.ecx.typing_env);
                         // Mutable pointer to immutable memory is no good.
                         if ptr_expected_mutbl == Mutability::Mut
                             && alloc_actual_mutbl == Mutability::Not
@@ -628,12 +630,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                             // This can actually occur with transmutes.
                             throw_validation_failure!(self.path, MutableRefToImmutable);
                         }
-                        // In a const, everything must be completely immutable.
+                        // In a const, any kind of mutable reference is not good.
                         if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. })) {
-                            if ptr_expected_mutbl == Mutability::Mut
-                                || alloc_actual_mutbl == Mutability::Mut
-                            {
-                                throw_validation_failure!(self.path, ConstRefToMutable);
+                            if ptr_expected_mutbl == Mutability::Mut {
+                                throw_validation_failure!(self.path, MutableRefInConst);
                             }
                         }
                     }
@@ -906,7 +906,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         let (_prov, start_offset) = mplace.ptr().into_parts();
         let (size, _align) = self
             .ecx
-            .size_and_align_of_mplace(&mplace)?
+            .size_and_align_of_val(&mplace)?
             .unwrap_or((mplace.layout.size, mplace.layout.align.abi));
         // If there is no padding at all, we can skip the rest: check for
         // a single data range covering the entire value.
@@ -1086,8 +1086,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
     ) -> InterpResult<'tcx> {
         // Special check for CTFE validation, preventing `UnsafeCell` inside unions in immutable memory.
         if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if !val.layout.is_zst() && !val.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.typing_env)
-            {
+            // Unsized unions are currently not a thing, but let's keep this code consistent with
+            // the check in `visit_value`.
+            let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
+            if !zst && !val.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.typing_env) {
                 if !self.in_mutable_memory(val) {
                     throw_validation_failure!(self.path, UnsafeCellInImmutable);
                 }
@@ -1131,7 +1133,10 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt,
 
         // Special check preventing `UnsafeCell` in the inner part of constants
         if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if !val.layout.is_zst()
+            // Exclude ZST values. We need to compute the dynamic size/align to properly
+            // handle slices and trait objects.
+            let zst = self.ecx.size_and_align_of_val(val)?.is_some_and(|(s, _a)| s.bytes() == 0);
+            if !zst
                 && let Some(def) = val.layout.ty.ty_adt_def()
                 && def.is_unsafe_cell()
             {
@@ -1364,8 +1369,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         })
     }
 
-    /// This function checks the data at `op` to be const-valid.
-    /// `op` is assumed to cover valid memory if it is an indirect operand.
+    /// This function checks the data at `val` to be const-valid.
+    /// `val` is assumed to cover valid memory if it is an indirect operand.
     /// It will error if the bits at the destination do not match the ones described by the layout.
     ///
     /// `ref_tracking` is used to record references that we encounter so that they
@@ -1391,8 +1396,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         )
     }
 
-    /// This function checks the data at `op` to be runtime-valid.
-    /// `op` is assumed to cover valid memory if it is an indirect operand.
+    /// This function checks the data at `val` to be runtime-valid.
+    /// `val` is assumed to cover valid memory if it is an indirect operand.
     /// It will error if the bits at the destination do not match the ones described by the layout.
     #[inline(always)]
     pub fn validate_operand(
@@ -1401,6 +1406,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         recursive: bool,
         reset_provenance_and_padding: bool,
     ) -> InterpResult<'tcx> {
+        let _span = enter_trace_span!(
+            M,
+            "validate_operand",
+            "recursive={recursive}, reset_provenance_and_padding={reset_provenance_and_padding}, val={val:?}"
+        );
+
         // Note that we *could* actually be in CTFE here with `-Zextra-const-ub-checks`, but it's
         // still correct to not use `ctfe_mode`: that mode is for validation of the final constant
         // value, it rules out things like `UnsafeCell` in awkward places.
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index 5aea91233bd..d5970b69baf 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -6,7 +6,6 @@ use std::num::NonZero;
 use rustc_abi::{FieldIdx, FieldsShape, VariantIdx, Variants};
 use rustc_index::IndexVec;
 use rustc_middle::mir::interpret::InterpResult;
-use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, Ty};
 use tracing::trace;