Merging upstream version 1.76.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

30 files changed, 614 insertions, 456 deletions

diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index f926da464..4a426ed16 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -461,6 +461,9 @@ const_eval_validation_uninhabited_val = {$front_matter}: encountered a value of
 const_eval_validation_uninit = {$front_matter}: encountered uninitialized memory, but {$expected}
 const_eval_validation_unsafe_cell = {$front_matter}: encountered `UnsafeCell` in a `const`
 
+const_eval_write_through_immutable_pointer =
+    writing through a pointer that was derived from a shared (immutable) reference
+
 const_eval_write_to_read_only =
     writing to {$allocation} which is read-only
 const_eval_zst_pointer_out_of_bounds =
diff --git a/compiler/rustc_const_eval/src/const_eval/error.rs b/compiler/rustc_const_eval/src/const_eval/error.rs
index bf1e0a370..8f18cd78d 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -1,14 +1,16 @@
 use std::mem;
 
 use rustc_errors::{DiagnosticArgValue, DiagnosticMessage, IntoDiagnostic, IntoDiagnosticArg};
+use rustc_hir::CRATE_HIR_ID;
 use rustc_middle::mir::AssertKind;
+use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::{layout::LayoutError, ConstInt};
 use rustc_span::{ErrorGuaranteed, Span, Symbol, DUMMY_SP};
 
-use super::InterpCx;
+use super::{CompileTimeInterpreter, InterpCx};
 use crate::errors::{self, FrameNote, ReportErrorExt};
-use crate::interpret::{ErrorHandled, InterpError, InterpErrorInfo, Machine, MachineStopType};
+use crate::interpret::{ErrorHandled, InterpError, InterpErrorInfo, MachineStopType};
 
 /// The CTFE machine has some custom error kinds.
 #[derive(Clone, Debug)]
@@ -57,16 +59,20 @@ impl<'tcx> Into<InterpErrorInfo<'tcx>> for ConstEvalErrKind {
     }
 }
 
-pub fn get_span_and_frames<'tcx, 'mir, M: Machine<'mir, 'tcx>>(
-    ecx: &InterpCx<'mir, 'tcx, M>,
+pub fn get_span_and_frames<'tcx, 'mir>(
+    tcx: TyCtxtAt<'tcx>,
+    machine: &CompileTimeInterpreter<'mir, 'tcx>,
 ) -> (Span, Vec<errors::FrameNote>)
 where
     'tcx: 'mir,
 {
-    let mut stacktrace = ecx.generate_stacktrace();
+    let mut stacktrace =
+        InterpCx::<CompileTimeInterpreter<'mir, 'tcx>>::generate_stacktrace_from_stack(
+            &machine.stack,
+        );
     // Filter out `requires_caller_location` frames.
-    stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(*ecx.tcx));
-    let span = stacktrace.first().map(|f| f.span).unwrap_or(ecx.tcx.span);
+    stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(*tcx));
+    let span = stacktrace.first().map(|f| f.span).unwrap_or(tcx.span);
 
     let mut frames = Vec::new();
 
@@ -87,7 +93,7 @@ where
 
         let mut last_frame: Option<errors::FrameNote> = None;
         for frame_info in &stacktrace {
-            let frame = frame_info.as_note(*ecx.tcx);
+            let frame = frame_info.as_note(*tcx);
             match last_frame.as_mut() {
                 Some(last_frame)
                     if last_frame.span == frame.span
@@ -148,7 +154,7 @@ where
             let mut err = tcx.sess.create_err(err);
 
             let msg = error.diagnostic_message();
-            error.add_args(&tcx.sess.parse_sess.span_diagnostic, &mut err);
+            error.add_args(tcx.sess.dcx(), &mut err);
 
             // Use *our* span to label the interp error
             err.span_label(our_span, msg);
@@ -156,3 +162,25 @@ where
         }
     }
 }
+
+/// Emit a lint from a const-eval situation.
+// Even if this is unused, please don't remove it -- chances are we will need to emit a lint during const-eval again in the future!
+pub(super) fn lint<'tcx, 'mir, L>(
+    tcx: TyCtxtAt<'tcx>,
+    machine: &CompileTimeInterpreter<'mir, 'tcx>,
+    lint: &'static rustc_session::lint::Lint,
+    decorator: impl FnOnce(Vec<errors::FrameNote>) -> L,
+) where
+    L: for<'a> rustc_errors::DecorateLint<'a, ()>,
+{
+    let (span, frames) = get_span_and_frames(tcx, machine);
+
+    tcx.emit_spanned_lint(
+        lint,
+        // We use the root frame for this so the crate that defines the const defines whether the
+        // lint is emitted.
+        machine.stack.first().and_then(|frame| frame.lint_root()).unwrap_or(CRATE_HIR_ID),
+        span,
+        decorator(frames),
+    );
+}
diff --git a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
index 13937a941..9d22df50d 100644
--- a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
@@ -155,8 +155,8 @@ pub(super) fn op_to_const<'tcx>(
     match immediate {
         Left(ref mplace) => {
             // We know `offset` is relative to the allocation, so we can use `into_parts`.
-            let (alloc_id, offset) = mplace.ptr().into_parts();
-            let alloc_id = alloc_id.expect("cannot have `fake` place fot non-ZST type");
+            let (prov, offset) = mplace.ptr().into_parts();
+            let alloc_id = prov.expect("cannot have `fake` place for non-ZST type").alloc_id();
             ConstValue::Indirect { alloc_id, offset }
         }
         // see comment on `let force_as_immediate` above
@@ -178,8 +178,8 @@ pub(super) fn op_to_const<'tcx>(
                 );
                 let msg = "`op_to_const` on an immediate scalar pair must only be used on slice references to the beginning of an actual allocation";
                 // We know `offset` is relative to the allocation, so we can use `into_parts`.
-                let (alloc_id, offset) = a.to_pointer(ecx).expect(msg).into_parts();
-                let alloc_id = alloc_id.expect(msg);
+                let (prov, offset) = a.to_pointer(ecx).expect(msg).into_parts();
+                let alloc_id = prov.expect(msg).alloc_id();
                 let data = ecx.tcx.global_alloc(alloc_id).unwrap_memory();
                 assert!(offset == abi::Size::ZERO, "{}", msg);
                 let meta = b.to_target_usize(ecx).expect(msg);
@@ -314,7 +314,7 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
     is_static: bool,
 ) -> ::rustc_middle::mir::interpret::EvalToAllocationRawResult<'tcx> {
     let res = ecx.load_mir(cid.instance.def, cid.promoted);
-    match res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, &body)) {
+    match res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, body)) {
         Err(error) => {
             let (error, backtrace) = error.into_parts();
             backtrace.print_backtrace();
@@ -338,7 +338,7 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
                 *ecx.tcx,
                 error,
                 None,
-                || super::get_span_and_frames(&ecx),
+                || super::get_span_and_frames(ecx.tcx, &ecx.machine),
                 |span, frames| ConstEvalError {
                     span,
                     error_kind: kind,
@@ -353,7 +353,7 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
             let validation =
                 const_validate_mplace(&ecx, &mplace, is_static, cid.promoted.is_some());
 
-            let alloc_id = mplace.ptr().provenance.unwrap();
+            let alloc_id = mplace.ptr().provenance.unwrap().alloc_id();
 
             // Validation failed, report an error.
             if let Err(error) = validation {
@@ -419,7 +419,7 @@ pub fn const_report_error<'mir, 'tcx>(
         *ecx.tcx,
         error,
         None,
-        || crate::const_eval::get_span_and_frames(ecx),
+        || crate::const_eval::get_span_and_frames(ecx.tcx, &ecx.machine),
         move |span, frames| errors::UndefinedBehavior { span, ub_note, frames, raw_bytes },
     )
 }
diff --git a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
index 9e992637f..dbc29e607 100644
--- a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
@@ -33,7 +33,7 @@ pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
 /// return if it has a `const` modifier. If it is an intrinsic, report whether said intrinsic
 /// has a `rustc_const_{un,}stable` attribute. Otherwise, return `Constness::NotConst`.
 fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
-    let node = tcx.hir().get_by_def_id(def_id);
+    let node = tcx.hir_node_by_def_id(def_id);
 
     match node {
         hir::Node::Ctor(_)
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index 4b447229c..9aaf6c510 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -1,30 +1,30 @@
-use rustc_hir::def::DefKind;
-use rustc_hir::LangItem;
-use rustc_middle::mir;
-use rustc_middle::mir::interpret::PointerArithmetic;
-use rustc_middle::ty::layout::{FnAbiOf, TyAndLayout};
-use rustc_middle::ty::{self, TyCtxt};
-use rustc_span::Span;
 use std::borrow::Borrow;
+use std::fmt;
 use std::hash::Hash;
 use std::ops::ControlFlow;
 
+use rustc_ast::Mutability;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::fx::IndexEntry;
-use std::fmt;
-
-use rustc_ast::Mutability;
+use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
+use rustc_hir::LangItem;
+use rustc_middle::mir;
 use rustc_middle::mir::AssertMessage;
+use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty;
+use rustc_middle::ty::layout::{FnAbiOf, TyAndLayout};
+use rustc_session::lint::builtin::WRITES_THROUGH_IMMUTABLE_POINTER;
 use rustc_span::symbol::{sym, Symbol};
+use rustc_span::Span;
 use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi as CallAbi;
 
 use crate::errors::{LongRunning, LongRunningWarn};
 use crate::fluent_generated as fluent;
 use crate::interpret::{
-    self, compile_time_machine, AllocId, ConstAllocation, FnArg, FnVal, Frame, ImmTy, InterpCx,
-    InterpResult, OpTy, PlaceTy, Pointer, Scalar,
+    self, compile_time_machine, AllocId, AllocRange, ConstAllocation, CtfeProvenance, FnArg, FnVal,
+    Frame, ImmTy, InterpCx, InterpResult, OpTy, PlaceTy, Pointer, PointerArithmetic, Scalar,
 };
 
 use super::error::*;
@@ -49,7 +49,7 @@ pub struct CompileTimeInterpreter<'mir, 'tcx> {
     pub(super) num_evaluated_steps: usize,
 
     /// The virtual call stack.
-    pub(super) stack: Vec<Frame<'mir, 'tcx, AllocId, ()>>,
+    pub(super) stack: Vec<Frame<'mir, 'tcx>>,
 
     /// We need to make sure consts never point to anything mutable, even recursively. That is
     /// relied on for pattern matching on consts with references.
@@ -108,6 +108,14 @@ impl<K: Hash + Eq, V> interpret::AllocMap<K, V> for FxIndexMap<K, V> {
     }
 
     #[inline(always)]
+    fn contains_key_ref<Q: ?Sized + Hash + Eq>(&self, k: &Q) -> bool
+    where
+        K: Borrow<Q>,
+    {
+        FxIndexMap::contains_key(self, k)
+    }
+
+    #[inline(always)]
     fn insert(&mut self, k: K, v: V) -> Option<V> {
         FxIndexMap::insert(self, k, v)
     }
@@ -192,7 +200,7 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
                 &caller
                     .file
                     .name
-                    .for_scope(&self.tcx.sess, RemapPathScopeComponents::DIAGNOSTICS)
+                    .for_scope(self.tcx.sess, RemapPathScopeComponents::DIAGNOSTICS)
                     .to_string_lossy(),
             ),
             u32::try_from(caller.line).unwrap(),
@@ -383,7 +391,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 if ecx.tcx.is_ctfe_mir_available(def) {
                     Ok(ecx.tcx.mir_for_ctfe(def))
                 } else if ecx.tcx.def_kind(def) == DefKind::AssocConst {
-                    let guar = ecx.tcx.sess.delay_span_bug(
+                    let guar = ecx.tcx.sess.span_delayed_bug(
                         rustc_span::DUMMY_SP,
                         "This is likely a const item that is missing from its impl",
                     );
@@ -485,7 +493,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 };
 
                 let ptr = ecx.allocate_ptr(
-                    Size::from_bytes(size as u64),
+                    Size::from_bytes(size),
                     align,
                     interpret::MemoryKind::Machine(MemoryKind::Heap),
                 )?;
@@ -614,7 +622,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                     let guard = ecx
                         .tcx
                         .sess
-                        .delay_span_bug(span, "The deny lint should have already errored");
+                        .span_delayed_bug(span, "The deny lint should have already errored");
                     throw_inval!(AlreadyReported(guard.into()));
                 }
             } else if new_steps > start && new_steps.is_power_of_two() {
@@ -630,10 +638,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
     }
 
     #[inline(always)]
-    fn expose_ptr(
-        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        _ptr: Pointer<AllocId>,
-    ) -> InterpResult<'tcx> {
+    fn expose_ptr(_ecx: &mut InterpCx<'mir, 'tcx, Self>, _ptr: Pointer) -> InterpResult<'tcx> {
         // This is only reachable with -Zunleash-the-miri-inside-of-you.
         throw_unsup_format!("exposing pointers is not possible at compile-time")
     }
@@ -666,7 +671,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
     }
 
     fn before_access_global(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         machine: &Self,
         alloc_id: AllocId,
         alloc: ConstAllocation<'tcx>,
@@ -703,6 +708,48 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             }
         }
     }
+
+    fn retag_ptr_value(
+        ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _kind: mir::RetagKind,
+        val: &ImmTy<'tcx, CtfeProvenance>,
+    ) -> InterpResult<'tcx, ImmTy<'tcx, CtfeProvenance>> {
+        // If it's a frozen shared reference that's not already immutable, make it immutable.
+        // (Do nothing on `None` provenance, that cannot store immutability anyway.)
+        if let ty::Ref(_, ty, mutbl) = val.layout.ty.kind()
+            && *mutbl == Mutability::Not
+            && val.to_scalar_and_meta().0.to_pointer(ecx)?.provenance.is_some_and(|p| !p.immutable())
+            // That next check is expensive, that's why we have all the guards above.
+            && ty.is_freeze(*ecx.tcx, ecx.param_env)
+        {
+            let place = ecx.ref_to_mplace(val)?;
+            let new_place = place.map_provenance(|p| p.map(CtfeProvenance::as_immutable));
+            Ok(ImmTy::from_immediate(new_place.to_ref(ecx), val.layout))
+        } else {
+            Ok(val.clone())
+        }
+    }
+
+    fn before_memory_write(
+        tcx: TyCtxtAt<'tcx>,
+        machine: &mut Self,
+        _alloc_extra: &mut Self::AllocExtra,
+        (_alloc_id, immutable): (AllocId, bool),
+        range: AllocRange,
+    ) -> InterpResult<'tcx> {
+        if range.size == Size::ZERO {
+            // Nothing to check.
+            return Ok(());
+        }
+        // Reject writes through immutable pointers.
+        if immutable {
+            super::lint(tcx, machine, WRITES_THROUGH_IMMUTABLE_POINTER, |frames| {
+                crate::errors::WriteThroughImmutablePointer { frames }
+            });
+        }
+        // Everything else is fine.
+        Ok(())
+    }
 }
 
 // Please do not add any code below the above `Machine` trait impl. I (oli-obk) plan more cleanups
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index ed2d81727..854fe9a07 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
@@ -11,7 +11,7 @@ use rustc_middle::mir;
 use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt};
 use rustc_span::DUMMY_SP;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{Abi, VariantIdx};
 
 #[instrument(skip(ecx), level = "debug")]
 fn branches<'tcx>(
@@ -101,11 +101,16 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
             // Not all raw pointers are allowed, as we cannot properly test them for
             // equality at compile-time (see `ptr_guaranteed_cmp`).
             // However we allow those that are just integers in disguise.
-            // (We could allow wide raw pointers where both sides are integers in the future,
-            // but for now we reject them.)
-            let Ok(val) = ecx.read_scalar(place) else {
+            // First, get the pointer. Remember it might be wide!
+            let Ok(val) = ecx.read_immediate(place) else {
                 return Err(ValTreeCreationError::Other);
             };
+            // We could allow wide raw pointers where both sides are integers in the future,
+            // but for now we reject them.
+            if matches!(val.layout.abi, Abi::ScalarPair(..)) {
+                return Err(ValTreeCreationError::Other);
+            }
+            let val = val.to_scalar();
             // We are in the CTFE machine, so ptr-to-int casts will fail.
             // This can only be `Ok` if `val` already is an integer.
             let Ok(val) = val.try_to_int() else {
@@ -382,7 +387,7 @@ fn valtree_into_mplace<'tcx>(
 
                 debug!(?place_inner);
                 valtree_into_mplace(ecx, &place_inner, *inner_valtree);
-                dump_place(&ecx, &place_inner);
+                dump_place(ecx, &place_inner);
             }
 
             debug!("dump of place_adjusted:");
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index cc8f33872..adce1f543 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -1,5 +1,5 @@
 use rustc_errors::{
-    DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee, Handler,
+    DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee,
     IntoDiagnostic,
 };
 use rustc_hir::ConstContext;
@@ -402,6 +402,13 @@ pub struct ConstEvalError {
     pub frame_notes: Vec<FrameNote>,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(const_eval_write_through_immutable_pointer)]
+pub struct WriteThroughImmutablePointer {
+    #[subdiagnostic]
+    pub frames: Vec<FrameNote>,
+}
+
 #[derive(Diagnostic)]
 #[diag(const_eval_nullary_intrinsic_fail)]
 pub struct NullaryIntrinsicError {
@@ -425,11 +432,7 @@ pub struct UndefinedBehavior {
 pub trait ReportErrorExt {
     /// Returns the diagnostic message for this error.
     fn diagnostic_message(&self) -> DiagnosticMessage;
-    fn add_args<G: EmissionGuarantee>(
-        self,
-        handler: &Handler,
-        builder: &mut DiagnosticBuilder<'_, G>,
-    );
+    fn add_args<G: EmissionGuarantee>(self, dcx: &DiagCtxt, builder: &mut DiagnosticBuilder<'_, G>);
 
     fn debug(self) -> String
     where
@@ -437,17 +440,17 @@ pub trait ReportErrorExt {
     {
         ty::tls::with(move |tcx| {
             let mut builder = tcx.sess.struct_allow(DiagnosticMessage::Str(String::new().into()));
-            let handler = &tcx.sess.parse_sess.span_diagnostic;
+            let dcx = tcx.sess.dcx();
             let message = self.diagnostic_message();
-            self.add_args(handler, &mut builder);
-            let s = handler.eagerly_translate_to_string(message, builder.args());
+            self.add_args(dcx, &mut builder);
+            let s = dcx.eagerly_translate_to_string(message, builder.args());
             builder.cancel();
             s
         })
     }
 }
 
-fn bad_pointer_message(msg: CheckInAllocMsg, handler: &Handler) -> String {
+fn bad_pointer_message(msg: CheckInAllocMsg, dcx: &DiagCtxt) -> String {
     use crate::fluent_generated::*;
 
     let msg = match msg {
@@ -457,7 +460,7 @@ fn bad_pointer_message(msg: CheckInAllocMsg, handler: &Handler) -> String {
         CheckInAllocMsg::InboundsTest => const_eval_in_bounds_test,
     };
 
-    handler.eagerly_translate_to_string(msg, [].into_iter())
+    dcx.eagerly_translate_to_string(msg, [].into_iter())
 }
 
 impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
@@ -507,7 +510,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
 
     fn add_args<G: EmissionGuarantee>(
         self,
-        handler: &Handler,
+        dcx: &DiagCtxt,
         builder: &mut DiagnosticBuilder<'_, G>,
     ) {
         use UndefinedBehaviorInfo::*;
@@ -518,7 +521,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
                     builder.set_arg(name, value);
                 });
             }
-            ValidationError(e) => e.add_args(handler, builder),
+            ValidationError(e) => e.add_args(dcx, builder),
 
             Unreachable
             | DivisionByZero
@@ -542,7 +545,7 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
             PointerUseAfterFree(alloc_id, msg) => {
                 builder
                     .set_arg("alloc_id", alloc_id)
-                    .set_arg("bad_pointer_message", bad_pointer_message(msg, handler));
+                    .set_arg("bad_pointer_message", bad_pointer_message(msg, dcx));
             }
             PointerOutOfBounds { alloc_id, alloc_size, ptr_offset, ptr_size, msg } => {
                 builder
@@ -550,14 +553,14 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
                     .set_arg("alloc_size", alloc_size.bytes())
                     .set_arg("ptr_offset", ptr_offset)
                     .set_arg("ptr_size", ptr_size.bytes())
-                    .set_arg("bad_pointer_message", bad_pointer_message(msg, handler));
+                    .set_arg("bad_pointer_message", bad_pointer_message(msg, dcx));
             }
             DanglingIntPointer(ptr, msg) => {
                 if ptr != 0 {
                     builder.set_arg("pointer", format!("{ptr:#x}[noalloc]"));
                 }
 
-                builder.set_arg("bad_pointer_message", bad_pointer_message(msg, handler));
+                builder.set_arg("bad_pointer_message", bad_pointer_message(msg, dcx));
             }
             AlignmentCheckFailed(Misalignment { required, has }, msg) => {
                 builder.set_arg("required", required.bytes());
@@ -671,7 +674,7 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
         }
     }
 
-    fn add_args<G: EmissionGuarantee>(self, handler: &Handler, err: &mut DiagnosticBuilder<'_, G>) {
+    fn add_args<G: EmissionGuarantee>(self, dcx: &DiagCtxt, err: &mut DiagnosticBuilder<'_, G>) {
         use crate::fluent_generated as fluent;
         use rustc_middle::mir::interpret::ValidationErrorKind::*;
 
@@ -681,12 +684,12 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
         }
 
         let message = if let Some(path) = self.path {
-            handler.eagerly_translate_to_string(
+            dcx.eagerly_translate_to_string(
                 fluent::const_eval_validation_front_matter_invalid_value_with_path,
                 [("path".into(), DiagnosticArgValue::Str(path.into()))].iter().map(|(a, b)| (a, b)),
             )
         } else {
-            handler.eagerly_translate_to_string(
+            dcx.eagerly_translate_to_string(
                 fluent::const_eval_validation_front_matter_invalid_value,
                 [].into_iter(),
             )
@@ -697,7 +700,7 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
         fn add_range_arg<G: EmissionGuarantee>(
             r: WrappingRange,
             max_hi: u128,
-            handler: &Handler,
+            dcx: &DiagCtxt,
             err: &mut DiagnosticBuilder<'_, G>,
         ) {
             let WrappingRange { start: lo, end: hi } = r;
@@ -721,7 +724,7 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
                 ("hi".into(), DiagnosticArgValue::Str(hi.to_string().into())),
             ];
             let args = args.iter().map(|(a, b)| (a, b));
-            let message = handler.eagerly_translate_to_string(msg, args);
+            let message = dcx.eagerly_translate_to_string(msg, args);
             err.set_arg("in_range", message);
         }
 
@@ -743,7 +746,7 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
                     ExpectedKind::EnumTag => fluent::const_eval_validation_expected_enum_tag,
                     ExpectedKind::Str => fluent::const_eval_validation_expected_str,
                 };
-                let msg = handler.eagerly_translate_to_string(msg, [].into_iter());
+                let msg = dcx.eagerly_translate_to_string(msg, [].into_iter());
                 err.set_arg("expected", msg);
             }
             InvalidEnumTag { value }
@@ -754,11 +757,11 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
                 err.set_arg("value", value);
             }
             NullablePtrOutOfRange { range, max_value } | PtrOutOfRange { range, max_value } => {
-                add_range_arg(range, max_value, handler, err)
+                add_range_arg(range, max_value, dcx, err)
             }
             OutOfRange { range, max_value, value } => {
                 err.set_arg("value", value);
-                add_range_arg(range, max_value, handler, err);
+                add_range_arg(range, max_value, dcx, err);
             }
             UnalignedPtr { required_bytes, found_bytes, .. } => {
                 err.set_arg("required_bytes", required_bytes);
@@ -797,7 +800,7 @@ impl ReportErrorExt for UnsupportedOpInfo {
             UnsupportedOpInfo::ReadExternStatic(_) => const_eval_read_extern_static,
         }
     }
-    fn add_args<G: EmissionGuarantee>(self, _: &Handler, builder: &mut DiagnosticBuilder<'_, G>) {
+    fn add_args<G: EmissionGuarantee>(self, _: &DiagCtxt, builder: &mut DiagnosticBuilder<'_, G>) {
         use crate::fluent_generated::*;
 
         use UnsupportedOpInfo::*;
@@ -832,14 +835,14 @@ impl<'tcx> ReportErrorExt for InterpError<'tcx> {
     }
     fn add_args<G: EmissionGuarantee>(
         self,
-        handler: &Handler,
+        dcx: &DiagCtxt,
         builder: &mut DiagnosticBuilder<'_, G>,
     ) {
         match self {
-            InterpError::UndefinedBehavior(ub) => ub.add_args(handler, builder),
-            InterpError::Unsupported(e) => e.add_args(handler, builder),
-            InterpError::InvalidProgram(e) => e.add_args(handler, builder),
-            InterpError::ResourceExhaustion(e) => e.add_args(handler, builder),
+            InterpError::UndefinedBehavior(ub) => ub.add_args(dcx, builder),
+            InterpError::Unsupported(e) => e.add_args(dcx, builder),
+            InterpError::InvalidProgram(e) => e.add_args(dcx, builder),
+            InterpError::ResourceExhaustion(e) => e.add_args(dcx, builder),
             InterpError::MachineStop(e) => e.add_args(&mut |name, value| {
                 builder.set_arg(name, value);
             }),
@@ -864,7 +867,7 @@ impl<'tcx> ReportErrorExt for InvalidProgramInfo<'tcx> {
     }
     fn add_args<G: EmissionGuarantee>(
         self,
-        handler: &Handler,
+        dcx: &DiagCtxt,
         builder: &mut DiagnosticBuilder<'_, G>,
     ) {
         match self {
@@ -872,7 +875,7 @@ impl<'tcx> ReportErrorExt for InvalidProgramInfo<'tcx> {
             | InvalidProgramInfo::AlreadyReported(_)
             | InvalidProgramInfo::ConstPropNonsense => {}
             InvalidProgramInfo::Layout(e) => {
-                let diag: DiagnosticBuilder<'_, ()> = e.into_diagnostic().into_diagnostic(handler);
+                let diag: DiagnosticBuilder<'_, ()> = e.into_diagnostic().into_diagnostic(dcx);
                 for (name, val) in diag.args() {
                     builder.set_arg(name.clone(), val.clone());
                 }
@@ -897,5 +900,5 @@ impl ReportErrorExt for ResourceExhaustionInfo {
             ResourceExhaustionInfo::AddressSpaceFull => const_eval_address_space_full,
         }
     }
-    fn add_args<G: EmissionGuarantee>(self, _: &Handler, _: &mut DiagnosticBuilder<'_, G>) {}
+    fn add_args<G: EmissionGuarantee>(self, _: &DiagCtxt, _: &mut DiagnosticBuilder<'_, G>) {}
 }
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index f4cb12c8d..d296ff592 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -256,7 +256,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let addr = addr.to_target_usize(self)?;
 
         // Then turn address into pointer.
-        let ptr = M::ptr_from_addr_cast(&self, addr)?;
+        let ptr = M::ptr_from_addr_cast(self, addr)?;
         Ok(ImmTy::from_scalar(Scalar::from_maybe_pointer(ptr, self), cast_to))
     }
 
diff --git a/compiler/rustc_const_eval/src/interpret/discriminant.rs b/compiler/rustc_const_eval/src/interpret/discriminant.rs
index fd1736703..d9f583c1d 100644
--- a/compiler/rustc_const_eval/src/interpret/discriminant.rs
+++ b/compiler/rustc_const_eval/src/interpret/discriminant.rs
@@ -119,7 +119,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     if matches!(ty.kind(), ty::Adt(def, ..) if def.variants().is_empty()) {
                         throw_ub!(UninhabitedEnumVariantRead(index))
                     }
-                    // For consisteny with `write_discriminant`, and to make sure that
+                    // For consistency with `write_discriminant`, and to make sure that
                     // `project_downcast` cannot fail due to strange layouts, we declare immediate UB
                     // for uninhabited variants.
                     if op.layout().for_variant(self, index).abi.is_uninhabited() {
@@ -236,7 +236,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 variant
             }
         };
-        // For consisteny with `write_discriminant`, and to make sure that `project_downcast` cannot fail due to strange layouts, we declare immediate UB for uninhabited variants.
+        // For consistency with `write_discriminant`, and to make sure that `project_downcast` cannot fail due to strange layouts, we declare immediate UB for uninhabited variants.
         if op.layout().for_variant(self, index).abi.is_uninhabited() {
             throw_ub!(UninhabitedEnumVariantRead(index))
         }
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index 07cab5e34..af8e5e7d1 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -7,7 +7,9 @@ use hir::CRATE_HIR_ID;
 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
 use rustc_index::IndexVec;
 use rustc_middle::mir;
-use rustc_middle::mir::interpret::{ErrorHandled, InvalidMetaKind, ReportedErrorInfo};
+use rustc_middle::mir::interpret::{
+    CtfeProvenance, ErrorHandled, InvalidMetaKind, ReportedErrorInfo,
+};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{
     self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
@@ -20,9 +22,9 @@ use rustc_span::Span;
 use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayout};
 
 use super::{
-    AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace,
-    MemPlaceMeta, Memory, MemoryKind, OpTy, Operand, Place, PlaceTy, Pointer, PointerArithmetic,
-    Projectable, Provenance, Scalar, StackPopJump,
+    GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace, MemPlaceMeta,
+    Memory, MemoryKind, OpTy, Operand, Place, PlaceTy, Pointer, PointerArithmetic, Projectable,
+    Provenance, Scalar, StackPopJump,
 };
 use crate::errors;
 use crate::util;
@@ -84,7 +86,7 @@ impl Drop for SpanGuard {
 }
 
 /// A stack frame.
-pub struct Frame<'mir, 'tcx, Prov: Provenance = AllocId, Extra = ()> {
+pub struct Frame<'mir, 'tcx, Prov: Provenance = CtfeProvenance, Extra = ()> {
     ////////////////////////////////////////////////////////////////////////////////
     // Function and callsite information
     ////////////////////////////////////////////////////////////////////////////////
@@ -156,7 +158,7 @@ pub enum StackPopCleanup {
 
 /// State of a local variable including a memoized layout
 #[derive(Clone)]
-pub struct LocalState<'tcx, Prov: Provenance = AllocId> {
+pub struct LocalState<'tcx, Prov: Provenance = CtfeProvenance> {
     value: LocalValue<Prov>,
     /// Don't modify if `Some`, this is only used to prevent computing the layout twice.
     /// Avoids computing the layout of locals that are never actually initialized.
@@ -173,8 +175,11 @@ impl<Prov: Provenance> std::fmt::Debug for LocalState<'_, Prov> {
 }
 
 /// Current value of a local variable
+///
+/// This does not store the type of the local; the type is given by `body.local_decls` and can never
+/// change, so by not storing here we avoid having to maintain that as an invariant.
 #[derive(Copy, Clone, Debug)] // Miri debug-prints these
-pub(super) enum LocalValue<Prov: Provenance = AllocId> {
+pub(super) enum LocalValue<Prov: Provenance = CtfeProvenance> {
     /// This local is not currently alive, and cannot be used at all.
     Dead,
     /// A normal, live local.
@@ -279,14 +284,12 @@ impl<'mir, 'tcx, Prov: Provenance, Extra> Frame<'mir, 'tcx, Prov, Extra> {
 impl<'tcx> fmt::Display for FrameInfo<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         ty::tls::with(|tcx| {
-            if tcx.def_key(self.instance.def_id()).disambiguated_data.data
-                == DefPathData::ClosureExpr
-            {
+            if tcx.def_key(self.instance.def_id()).disambiguated_data.data == DefPathData::Closure {
                 write!(f, "inside closure")
             } else {
-                // Note: this triggers a `good_path_bug` state, which means that if we ever get here
-                // we must emit a diagnostic. We should never display a `FrameInfo` unless we
-                // actually want to emit a warning or error to the user.
+                // Note: this triggers a `good_path_delayed_bug` state, which means that if we ever
+                // get here we must emit a diagnostic. We should never display a `FrameInfo` unless
+                // we actually want to emit a warning or error to the user.
                 write!(f, "inside `{}`", self.instance)
             }
         })
@@ -296,12 +299,12 @@ impl<'tcx> fmt::Display for FrameInfo<'tcx> {
 impl<'tcx> FrameInfo<'tcx> {
     pub fn as_note(&self, tcx: TyCtxt<'tcx>) -> errors::FrameNote {
         let span = self.span;
-        if tcx.def_key(self.instance.def_id()).disambiguated_data.data == DefPathData::ClosureExpr {
+        if tcx.def_key(self.instance.def_id()).disambiguated_data.data == DefPathData::Closure {
             errors::FrameNote { where_: "closure", span, instance: String::new(), times: 0 }
         } else {
             let instance = format!("{}", self.instance);
-            // Note: this triggers a `good_path_bug` state, which means that if we ever get here
-            // we must emit a diagnostic. We should never display a `FrameInfo` unless we
+            // Note: this triggers a `good_path_delayed_bug` state, which means that if we ever get
+            // here we must emit a diagnostic. We should never display a `FrameInfo` unless we
             // actually want to emit a warning or error to the user.
             errors::FrameNote { where_: "instance", span, instance, times: 0 }
         }
@@ -456,7 +459,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         self.stack()
             .iter()
             .find_map(|frame| frame.body.source.def_id().as_local())
-            .map_or(CRATE_HIR_ID, |def_id| self.tcx.hir().local_def_id_to_hir_id(def_id))
+            .map_or(CRATE_HIR_ID, |def_id| self.tcx.local_def_id_to_hir_id(def_id))
     }
 
     /// Turn the given error into a human-readable string. Expects the string to be printed, so if
@@ -470,12 +473,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         backtrace.print_backtrace();
         // FIXME(fee1-dead), HACK: we want to use the error as title therefore we can just extract the
         // label and arguments from the InterpError.
-        let handler = &self.tcx.sess.parse_sess.span_diagnostic;
+        let dcx = self.tcx.sess.dcx();
         #[allow(rustc::untranslatable_diagnostic)]
         let mut diag = self.tcx.sess.struct_allow("");
         let msg = e.diagnostic_message();
-        e.add_args(handler, &mut diag);
-        let s = handler.eagerly_translate_to_string(msg, diag.args());
+        e.add_args(dcx, &mut diag);
+        let s = dcx.eagerly_translate_to_string(msg, diag.args());
         diag.cancel();
         s
     }
@@ -683,14 +686,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 assert!(layout.fields.count() > 0);
                 trace!("DST layout: {:?}", layout);
 
-                let sized_size = layout.fields.offset(layout.fields.count() - 1);
+                let unsized_offset_unadjusted = layout.fields.offset(layout.fields.count() - 1);
                 let sized_align = layout.align.abi;
-                trace!(
-                    "DST {} statically sized prefix size: {:?} align: {:?}",
-                    layout.ty,
-                    sized_size,
-                    sized_align
-                );
 
                 // Recurse to get the size of the dynamically sized field (must be
                 // the last field). Can't have foreign types here, how would we
@@ -704,36 +701,35 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     return Ok(None);
                 };
 
-                // FIXME (#26403, #27023): We should be adding padding
-                // to `sized_size` (to accommodate the `unsized_align`
-                // required of the unsized field that follows) before
-                // summing it with `sized_size`. (Note that since #26403
-                // is unfixed, we do not yet add the necessary padding
-                // here. But this is where the add would go.)
-
-                // Return the sum of sizes and max of aligns.
-                let size = sized_size + unsized_size; // `Size` addition
+                // # First compute the dynamic alignment
 
-                // Packed types ignore the alignment of their fields.
+                // Packed type alignment needs to be capped.
                 if let ty::Adt(def, _) = layout.ty.kind() {
-                    if def.repr().packed() {
-                        unsized_align = sized_align;
+                    if let Some(packed) = def.repr().pack {
+                        unsized_align = unsized_align.min(packed);
                     }
                 }
 
                 // Choose max of two known alignments (combined value must
                 // be aligned according to more restrictive of the two).
-                let align = sized_align.max(unsized_align);
+                let full_align = sized_align.max(unsized_align);
 
-                // Issue #27023: must add any necessary padding to `size`
-                // (to make it a multiple of `align`) before returning it.
-                let size = size.align_to(align);
+                // # Then compute the dynamic size
+
+                let unsized_offset_adjusted = unsized_offset_unadjusted.align_to(unsized_align);
+                let full_size = (unsized_offset_adjusted + unsized_size).align_to(full_align);
+
+                // Just for our sanitiy's sake, assert that this is equal to what codegen would compute.
+                assert_eq!(
+                    full_size,
+                    (unsized_offset_unadjusted + unsized_size).align_to(full_align)
+                );
 
                 // Check if this brought us over the size limit.
-                if size > self.max_size_of_val() {
+                if full_size > self.max_size_of_val() {
                     throw_ub!(InvalidMeta(InvalidMetaKind::TooBig));
                 }
-                Ok(Some((size, align)))
+                Ok(Some((full_size, full_align)))
             }
             ty::Dynamic(_, _, ty::Dyn) => {
                 let vtable = metadata.unwrap_meta().to_pointer(self)?;
diff --git a/compiler/rustc_const_eval/src/interpret/intern.rs b/compiler/rustc_const_eval/src/interpret/intern.rs
index 3d90e95c0..7931789e4 100644
--- a/compiler/rustc_const_eval/src/interpret/intern.rs
+++ b/compiler/rustc_const_eval/src/interpret/intern.rs
@@ -18,7 +18,7 @@ use super::validity::RefTracking;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
-use rustc_middle::mir::interpret::InterpResult;
+use rustc_middle::mir::interpret::{CtfeProvenance, InterpResult};
 use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
 
 use rustc_ast::Mutability;
@@ -34,7 +34,7 @@ pub trait CompileTimeMachine<'mir, 'tcx: 'mir, T> = Machine<
         'mir,
         'tcx,
         MemoryKind = T,
-        Provenance = AllocId,
+        Provenance = CtfeProvenance,
         ExtraFnVal = !,
         FrameExtra = (),
         AllocExtra = (),
@@ -94,9 +94,9 @@ fn intern_shallow<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval:
         // If the pointer is dangling (neither in local nor global memory), we leave it
         // to validation to error -- it has the much better error messages, pointing out where
         // in the value the dangling reference lies.
-        // The `delay_span_bug` ensures that we don't forget such a check in validation.
+        // The `span_delayed_bug` ensures that we don't forget such a check in validation.
         if tcx.try_get_global_alloc(alloc_id).is_none() {
-            tcx.sess.delay_span_bug(ecx.tcx.span, "tried to intern dangling pointer");
+            tcx.sess.span_delayed_bug(ecx.tcx.span, "tried to intern dangling pointer");
         }
         // treat dangling pointers like other statics
         // just to stop trying to recurse into them
@@ -135,7 +135,7 @@ fn intern_shallow<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval:
         alloc.mutability = Mutability::Not;
     };
     // link the alloc id to the actual allocation
-    leftover_allocations.extend(alloc.provenance().ptrs().iter().map(|&(_, alloc_id)| alloc_id));
+    leftover_allocations.extend(alloc.provenance().ptrs().iter().map(|&(_, prov)| prov.alloc_id()));
     let alloc = tcx.mk_const_alloc(alloc);
     tcx.set_alloc_id_memory(alloc_id, alloc);
     None
@@ -178,20 +178,20 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
                 tcx.struct_tail_erasing_lifetimes(referenced_ty, self.ecx.param_env).kind()
             {
                 let ptr = mplace.meta().unwrap_meta().to_pointer(&tcx)?;
-                if let Some(alloc_id) = ptr.provenance {
+                if let Some(prov) = ptr.provenance {
                     // Explicitly choose const mode here, since vtables are immutable, even
                     // if the reference of the fat pointer is mutable.
-                    self.intern_shallow(alloc_id, InternMode::Const, None);
+                    self.intern_shallow(prov.alloc_id(), InternMode::Const, None);
                 } else {
                     // Validation will error (with a better message) on an invalid vtable pointer.
                     // Let validation show the error message, but make sure it *does* error.
                     tcx.sess
-                        .delay_span_bug(tcx.span, "vtables pointers cannot be integer pointers");
+                        .span_delayed_bug(tcx.span, "vtables pointers cannot be integer pointers");
                 }
             }
             // Check if we have encountered this pointer+layout combination before.
             // Only recurse for allocation-backed pointers.
-            if let Some(alloc_id) = mplace.ptr().provenance {
+            if let Some(prov) = mplace.ptr().provenance {
                 // Compute the mode with which we intern this. Our goal here is to make as many
                 // statics as we can immutable so they can be placed in read-only memory by LLVM.
                 let ref_mode = match self.mode {
@@ -234,7 +234,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
                         InternMode::Const
                     }
                 };
-                match self.intern_shallow(alloc_id, ref_mode, Some(referenced_ty)) {
+                match self.intern_shallow(prov.alloc_id(), ref_mode, Some(referenced_ty)) {
                     // No need to recurse, these are interned already and statics may have
                     // cycles, so we don't want to recurse there
                     Some(IsStaticOrFn) => {}
@@ -259,7 +259,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
                 // to avoid could be expensive: on the potentially larger types, arrays and slices,
                 // rather than on all aggregates unconditionally.
                 if matches!(mplace.layout.ty.kind(), ty::Array(..) | ty::Slice(..)) {
-                    let Some((size, _align)) = self.ecx.size_and_align_of_mplace(&mplace)? else {
+                    let Some((size, _align)) = self.ecx.size_and_align_of_mplace(mplace)? else {
                         // We do the walk if we can't determine the size of the mplace: we may be
                         // dealing with extern types here in the future.
                         return Ok(true);
@@ -353,7 +353,7 @@ pub fn intern_const_alloc_recursive<
         leftover_allocations,
         // The outermost allocation must exist, because we allocated it with
         // `Memory::allocate`.
-        ret.ptr().provenance.unwrap(),
+        ret.ptr().provenance.unwrap().alloc_id(),
         base_intern_mode,
         Some(ret.layout.ty),
     );
@@ -375,7 +375,7 @@ pub fn intern_const_alloc_recursive<
         match res {
             Ok(()) => {}
             Err(error) => {
-                ecx.tcx.sess.delay_span_bug(
+                ecx.tcx.sess.span_delayed_bug(
                     ecx.tcx.span,
                     format!(
                         "error during interning should later cause validation failure: {}",
@@ -431,7 +431,8 @@ pub fn intern_const_alloc_recursive<
             }
             let alloc = tcx.mk_const_alloc(alloc);
             tcx.set_alloc_id_memory(alloc_id, alloc);
-            for &(_, alloc_id) in alloc.inner().provenance().ptrs().iter() {
+            for &(_, prov) in alloc.inner().provenance().ptrs().iter() {
+                let alloc_id = prov.alloc_id();
                 if leftover_allocations.insert(alloc_id) {
                     todo.push(alloc_id);
                 }
@@ -503,10 +504,11 @@ impl<'mir, 'tcx: 'mir, M: super::intern::CompileTimeMachine<'mir, 'tcx, !>>
         // `allocate` picks a fresh AllocId that we will associate with its data below.
         let dest = self.allocate(layout, MemoryKind::Stack)?;
         f(self, &dest.clone().into())?;
-        let mut alloc = self.memory.alloc_map.remove(&dest.ptr().provenance.unwrap()).unwrap().1;
+        let mut alloc =
+            self.memory.alloc_map.remove(&dest.ptr().provenance.unwrap().alloc_id()).unwrap().1;
         alloc.mutability = Mutability::Not;
         let alloc = self.tcx.mk_const_alloc(alloc);
-        let alloc_id = dest.ptr().provenance.unwrap(); // this was just allocated, it must have provenance
+        let alloc_id = dest.ptr().provenance.unwrap().alloc_id(); // this was just allocated, it must have provenance
         self.tcx.set_alloc_id_memory(alloc_id, alloc);
         Ok(alloc_id)
     }
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index b23cafc19..c29f23b91 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -3,17 +3,22 @@
 //! and miri.
 
 use rustc_hir::def_id::DefId;
-use rustc_middle::mir::{
-    self,
-    interpret::{Allocation, ConstAllocation, GlobalId, InterpResult, PointerArithmetic, Scalar},
-    BinOp, ConstValue, NonDivergingIntrinsic,
-};
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf as _, ValidityRequirement};
 use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_middle::{
+    mir::{
+        self,
+        interpret::{
+            Allocation, ConstAllocation, GlobalId, InterpResult, PointerArithmetic, Scalar,
+        },
+        BinOp, ConstValue, NonDivergingIntrinsic,
+    },
+    ty::layout::TyAndLayout,
+};
 use rustc_span::symbol::{sym, Symbol};
-use rustc_target::abi::{Abi, Primitive, Size};
+use rustc_target::abi::Size;
 
 use super::{
     util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx, Machine, OpTy, PlaceTy,
@@ -22,23 +27,6 @@ use super::{
 
 use crate::fluent_generated as fluent;
 
-fn numeric_intrinsic<Prov>(name: Symbol, bits: u128, kind: Primitive) -> Scalar<Prov> {
-    let size = match kind {
-        Primitive::Int(integer, _) => integer.size(),
-        _ => bug!("invalid `{}` argument: {:?}", name, bits),
-    };
-    let extra = 128 - u128::from(size.bits());
-    let bits_out = match name {
-        sym::ctpop => u128::from(bits.count_ones()),
-        sym::ctlz => u128::from(bits.leading_zeros()) - extra,
-        sym::cttz => u128::from((bits << extra).trailing_zeros()) - extra,
-        sym::bswap => (bits << extra).swap_bytes(),
-        sym::bitreverse => (bits << extra).reverse_bits(),
-        _ => bug!("not a numeric intrinsic: {}", name),
-    };
-    Scalar::from_uint(bits_out, size)
-}
-
 /// Directly returns an `Allocation` containing an absolute path representation of the given type.
 pub(crate) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ConstAllocation<'tcx> {
     let path = crate::util::type_name(tcx, ty);
@@ -179,30 +167,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             | sym::bswap
             | sym::bitreverse => {
                 let ty = instance_args.type_at(0);
-                let layout_of = self.layout_of(ty)?;
+                let layout = self.layout_of(ty)?;
                 let val = self.read_scalar(&args[0])?;
-                let bits = val.to_bits(layout_of.size)?;
-                let kind = match layout_of.abi {
-                    Abi::Scalar(scalar) => scalar.primitive(),
-                    _ => span_bug!(
-                        self.cur_span(),
-                        "{} called on invalid type {:?}",
-                        intrinsic_name,
-                        ty
-                    ),
-                };
-                let (nonzero, actual_intrinsic_name) = match intrinsic_name {
-                    sym::cttz_nonzero => (true, sym::cttz),
-                    sym::ctlz_nonzero => (true, sym::ctlz),
-                    other => (false, other),
-                };
-                if nonzero && bits == 0 {
-                    throw_ub_custom!(
-                        fluent::const_eval_call_nonzero_intrinsic,
-                        name = intrinsic_name,
-                    );
-                }
-                let out_val = numeric_intrinsic(actual_intrinsic_name, bits, kind);
+                let out_val = self.numeric_intrinsic(intrinsic_name, val, layout)?;
                 self.write_scalar(out_val, dest)?;
             }
             sym::saturating_add | sym::saturating_sub => {
@@ -493,6 +460,29 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
     }
 
+    pub fn numeric_intrinsic(
+        &self,
+        name: Symbol,
+        val: Scalar<M::Provenance>,
+        layout: TyAndLayout<'tcx>,
+    ) -> InterpResult<'tcx, Scalar<M::Provenance>> {
+        assert!(layout.ty.is_integral(), "invalid type for numeric intrinsic: {}", layout.ty);
+        let bits = val.to_bits(layout.size)?;
+        let extra = 128 - u128::from(layout.size.bits());
+        let bits_out = match name {
+            sym::ctpop => u128::from(bits.count_ones()),
+            sym::ctlz_nonzero | sym::cttz_nonzero if bits == 0 => {
+                throw_ub_custom!(fluent::const_eval_call_nonzero_intrinsic, name = name,);
+            }
+            sym::ctlz | sym::ctlz_nonzero => u128::from(bits.leading_zeros()) - extra,
+            sym::cttz | sym::cttz_nonzero => u128::from((bits << extra).trailing_zeros()) - extra,
+            sym::bswap => (bits << extra).swap_bytes(),
+            sym::bitreverse => (bits << extra).reverse_bits(),
+            _ => bug!("not a numeric intrinsic: {}", name),
+        };
+        Ok(Scalar::from_uint(bits_out, layout.size))
+    }
+
     pub fn exact_div(
         &mut self,
         a: &ImmTy<'tcx, M::Provenance>,
@@ -505,7 +495,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Performs an exact division, resulting in undefined behavior where
         // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`.
         // First, check x % y != 0 (or if that computation overflows).
-        let (res, overflow) = self.overflowing_binary_op(BinOp::Rem, &a, &b)?;
+        let (res, overflow) = self.overflowing_binary_op(BinOp::Rem, a, b)?;
         assert!(!overflow); // All overflow is UB, so this should never return on overflow.
         if res.to_scalar().assert_bits(a.layout.size) != 0 {
             throw_ub_custom!(
@@ -515,7 +505,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             )
         }
         // `Rem` says this is all right, so we can let `Div` do its job.
-        self.binop_ignore_overflow(BinOp::Div, &a, &b, dest)
+        self.binop_ignore_overflow(BinOp::Div, a, b, dest)
     }
 
     pub fn saturating_arith(
diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs
index 61fe9151d..5e6996551 100644
--- a/compiler/rustc_const_eval/src/interpret/machine.rs
+++ b/compiler/rustc_const_eval/src/interpret/machine.rs
@@ -9,15 +9,17 @@ use std::hash::Hash;
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_middle::mir;
+use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty;
 use rustc_middle::ty::layout::TyAndLayout;
-use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::def_id::DefId;
-use rustc_target::abi::Size;
+use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi as CallAbi;
 
 use super::{
-    AllocBytes, AllocId, AllocRange, Allocation, ConstAllocation, FnArg, Frame, ImmTy, InterpCx,
-    InterpResult, MPlaceTy, MemoryKind, OpTy, PlaceTy, Pointer, Provenance,
+    AllocBytes, AllocId, AllocKind, AllocRange, Allocation, ConstAllocation, CtfeProvenance, FnArg,
+    Frame, ImmTy, InterpCx, InterpResult, MPlaceTy, MemoryKind, Misalignment, OpTy, PlaceTy,
+    Pointer, Provenance,
 };
 
 /// Data returned by Machine::stack_pop,
@@ -49,6 +51,14 @@ pub trait AllocMap<K: Hash + Eq, V> {
     where
         K: Borrow<Q>;
 
+    /// Callers should prefer [`AllocMap::contains_key`] when it is possible to call because it may
+    /// be more efficient. This function exists for callers that only have a shared reference
+    /// (which might make it slightly less efficient than `contains_key`, e.g. if
+    /// the data is stored inside a `RefCell`).
+    fn contains_key_ref<Q: ?Sized + Hash + Eq>(&self, k: &Q) -> bool
+    where
+        K: Borrow<Q>;
+
     /// Inserts a new entry into the map.
     fn insert(&mut self, k: K, v: V) -> Option<V>;
 
@@ -135,11 +145,18 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// Whether memory accesses should be alignment-checked.
     fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
 
-    /// Whether, when checking alignment, we should look at the actual address and thus support
-    /// custom alignment logic based on whatever the integer address happens to be.
-    ///
-    /// If this returns true, Provenance::OFFSET_IS_ADDR must be true.
-    fn use_addr_for_alignment_check(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
+    /// Gives the machine a chance to detect more misalignment than the built-in checks would catch.
+    #[inline(always)]
+    fn alignment_check(
+        _ecx: &InterpCx<'mir, 'tcx, Self>,
+        _alloc_id: AllocId,
+        _alloc_align: Align,
+        _alloc_kind: AllocKind,
+        _offset: Size,
+        _align: Align,
+    ) -> Option<Misalignment> {
+        None
+    }
 
     /// Whether to enforce the validity invariant for a specific layout.
     fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>, layout: TyAndLayout<'tcx>) -> bool;
@@ -277,7 +294,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// `def_id` is `Some` if this is the "lazy" allocation of a static.
     #[inline]
     fn before_access_global(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &Self,
         _alloc_id: AllocId,
         _allocation: ConstAllocation<'tcx>,
@@ -372,7 +389,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// need to mutate.
     #[inline(always)]
     fn before_memory_read(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &Self,
         _alloc_extra: &Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -384,7 +401,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// Hook for performing extra checks on a memory write access.
     #[inline(always)]
     fn before_memory_write(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &mut Self,
         _alloc_extra: &mut Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -396,7 +413,7 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
     /// Hook for performing extra operations on a memory deallocation.
     #[inline(always)]
     fn before_memory_deallocation(
-        _tcx: TyCtxt<'tcx>,
+        _tcx: TyCtxtAt<'tcx>,
         _machine: &mut Self,
         _alloc_extra: &mut Self::AllocExtra,
         _prov: (AllocId, Self::ProvenanceExtra),
@@ -498,8 +515,8 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
 /// A lot of the flexibility above is just needed for `Miri`, but all "compile-time" machines
 /// (CTFE and ConstProp) use the same instance. Here, we share that code.
 pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
-    type Provenance = AllocId;
-    type ProvenanceExtra = ();
+    type Provenance = CtfeProvenance;
+    type ProvenanceExtra = bool; // the "immutable" flag
 
     type ExtraFnVal = !;
 
@@ -512,12 +529,6 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     type Bytes = Box<[u8]>;
 
     #[inline(always)]
-    fn use_addr_for_alignment_check(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
-        // We do not support `use_addr`.
-        false
-    }
-
-    #[inline(always)]
     fn ignore_optional_overflow_checks(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
         false
     }
@@ -558,14 +569,14 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
         def_id: DefId,
     ) -> InterpResult<$tcx, Pointer> {
         // Use the `AllocId` associated with the `DefId`. Any actual *access* will fail.
-        Ok(Pointer::new(ecx.tcx.reserve_and_set_static_alloc(def_id), Size::ZERO))
+        Ok(Pointer::new(ecx.tcx.reserve_and_set_static_alloc(def_id).into(), Size::ZERO))
     }
 
     #[inline(always)]
     fn adjust_alloc_base_pointer(
         _ecx: &InterpCx<$mir, $tcx, Self>,
-        ptr: Pointer<AllocId>,
-    ) -> InterpResult<$tcx, Pointer<AllocId>> {
+        ptr: Pointer<CtfeProvenance>,
+    ) -> InterpResult<$tcx, Pointer<CtfeProvenance>> {
         Ok(ptr)
     }
 
@@ -573,7 +584,7 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     fn ptr_from_addr_cast(
         _ecx: &InterpCx<$mir, $tcx, Self>,
         addr: u64,
-    ) -> InterpResult<$tcx, Pointer<Option<AllocId>>> {
+    ) -> InterpResult<$tcx, Pointer<Option<CtfeProvenance>>> {
         // Allow these casts, but make the pointer not dereferenceable.
         // (I.e., they behave like transmutation.)
         // This is correct because no pointers can ever be exposed in compile-time evaluation.
@@ -583,10 +594,10 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
     #[inline(always)]
     fn ptr_get_alloc(
         _ecx: &InterpCx<$mir, $tcx, Self>,
-        ptr: Pointer<AllocId>,
+        ptr: Pointer<CtfeProvenance>,
     ) -> Option<(AllocId, Size, Self::ProvenanceExtra)> {
         // We know `offset` is relative to the allocation, so we can use `into_parts`.
-        let (alloc_id, offset) = ptr.into_parts();
-        Some((alloc_id, offset, ()))
+        let (prov, offset) = ptr.into_parts();
+        Some((prov.alloc_id(), offset, prov.immutable()))
     }
 }
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index 16905e93b..3fde6ae9b 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -22,8 +22,8 @@ use crate::fluent_generated as fluent;
 
 use super::{
     alloc_range, AllocBytes, AllocId, AllocMap, AllocRange, Allocation, CheckAlignMsg,
-    CheckInAllocMsg, GlobalAlloc, InterpCx, InterpResult, Machine, MayLeak, Misalignment, Pointer,
-    PointerArithmetic, Provenance, Scalar,
+    CheckInAllocMsg, CtfeProvenance, GlobalAlloc, InterpCx, InterpResult, Machine, MayLeak,
+    Misalignment, Pointer, PointerArithmetic, Provenance, Scalar,
 };
 
 #[derive(Debug, PartialEq, Copy, Clone)]
@@ -58,6 +58,7 @@ impl<T: fmt::Display> fmt::Display for MemoryKind<T> {
 }
 
 /// The return value of `get_alloc_info` indicates the "kind" of the allocation.
+#[derive(Copy, Clone, PartialEq, Debug)]
 pub enum AllocKind {
     /// A regular live data allocation.
     LiveData,
@@ -158,9 +159,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     #[inline]
     pub fn global_base_pointer(
         &self,
-        ptr: Pointer<AllocId>,
+        ptr: Pointer<CtfeProvenance>,
     ) -> InterpResult<'tcx, Pointer<M::Provenance>> {
-        let alloc_id = ptr.provenance;
+        let alloc_id = ptr.provenance.alloc_id();
         // We need to handle `extern static`.
         match self.tcx.try_get_global_alloc(alloc_id) {
             Some(GlobalAlloc::Static(def_id)) if self.tcx.is_thread_local_static(def_id) => {
@@ -338,7 +339,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Let the machine take some extra action
         let size = alloc.size();
         M::before_memory_deallocation(
-            *self.tcx,
+            self.tcx,
             &mut self.machine,
             &mut alloc.extra,
             (alloc_id, prov),
@@ -473,8 +474,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         match self.ptr_try_get_alloc_id(ptr) {
             Err(addr) => offset_misalignment(addr, align),
             Ok((alloc_id, offset, _prov)) => {
-                let (_size, alloc_align, _kind) = self.get_alloc_info(alloc_id);
-                if M::use_addr_for_alignment_check(self) {
+                let (_size, alloc_align, kind) = self.get_alloc_info(alloc_id);
+                if let Some(misalign) =
+                    M::alignment_check(self, alloc_id, alloc_align, kind, offset, align)
+                {
+                    Some(misalign)
+                } else if M::Provenance::OFFSET_IS_ADDR {
                     // `use_addr_for_alignment_check` can only be true if `OFFSET_IS_ADDR` is true.
                     offset_misalignment(ptr.addr().bytes(), align)
                 } else {
@@ -501,6 +506,17 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     }
 }
 
+impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
+    /// This function is used by Miri's provenance GC to remove unreachable entries from the dead_alloc_map.
+    pub fn remove_unreachable_allocs(&mut self, reachable_allocs: &FxHashSet<AllocId>) {
+        // Unlike all the other GC helpers where we check if an `AllocId` is found in the interpreter or
+        // is live, here all the IDs in the map are for dead allocations so we don't
+        // need to check for liveness.
+        #[allow(rustc::potential_query_instability)] // Only used from Miri, not queries.
+        self.memory.dead_alloc_map.retain(|id, _| reachable_allocs.contains(id));
+    }
+}
+
 /// Allocation accessors
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// Helper function to obtain a global (tcx) allocation.
@@ -545,7 +561,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 (val, Some(def_id))
             }
         };
-        M::before_access_global(*self.tcx, &self.machine, id, alloc, def_id, is_write)?;
+        M::before_access_global(self.tcx, &self.machine, id, alloc, def_id, is_write)?;
         // We got tcx memory. Let the machine initialize its "extra" stuff.
         M::adjust_allocation(
             self,
@@ -610,7 +626,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         )?;
         if let Some((alloc_id, offset, prov, alloc)) = ptr_and_alloc {
             let range = alloc_range(offset, size);
-            M::before_memory_read(*self.tcx, &self.machine, &alloc.extra, (alloc_id, prov), range)?;
+            M::before_memory_read(self.tcx, &self.machine, &alloc.extra, (alloc_id, prov), range)?;
             Ok(Some(AllocRef { alloc, range, tcx: *self.tcx, alloc_id }))
         } else {
             // Even in this branch we have to be sure that we actually access the allocation, in
@@ -671,13 +687,13 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     {
         let parts = self.get_ptr_access(ptr, size)?;
         if let Some((alloc_id, offset, prov)) = parts {
-            let tcx = *self.tcx;
+            let tcx = self.tcx;
             // FIXME: can we somehow avoid looking up the allocation twice here?
             // We cannot call `get_raw_mut` inside `check_and_deref_ptr` as that would duplicate `&mut self`.
             let (alloc, machine) = self.get_alloc_raw_mut(alloc_id)?;
             let range = alloc_range(offset, size);
             M::before_memory_write(tcx, machine, &mut alloc.extra, (alloc_id, prov), range)?;
-            Ok(Some(AllocRefMut { alloc, range, tcx, alloc_id }))
+            Ok(Some(AllocRefMut { alloc, range, tcx: *tcx, alloc_id }))
         } else {
             Ok(None)
         }
@@ -692,6 +708,15 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         Ok((&mut alloc.extra, machine))
     }
 
+    /// Check whether an allocation is live. This is faster than calling
+    /// [`InterpCx::get_alloc_info`] if all you need to check is whether the kind is
+    /// [`AllocKind::Dead`] because it doesn't have to look up the type and layout of statics.
+    pub fn is_alloc_live(&self, id: AllocId) -> bool {
+        self.tcx.try_get_global_alloc(id).is_some()
+            || self.memory.alloc_map.contains_key_ref(&id)
+            || self.memory.extra_fn_ptr_map.contains_key(&id)
+    }
+
     /// Obtain the size and alignment of an allocation, even if that allocation has
     /// been deallocated.
     pub fn get_alloc_info(&self, id: AllocId) -> (Size, Align, AllocKind) {
@@ -1108,7 +1133,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let src_alloc = self.get_alloc_raw(src_alloc_id)?;
         let src_range = alloc_range(src_offset, size);
         M::before_memory_read(
-            *tcx,
+            tcx,
             &self.machine,
             &src_alloc.extra,
             (src_alloc_id, src_prov),
@@ -1138,7 +1163,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let (dest_alloc, extra) = self.get_alloc_raw_mut(dest_alloc_id)?;
         let dest_range = alloc_range(dest_offset, size * num_copies);
         M::before_memory_write(
-            *tcx,
+            tcx,
             extra,
             &mut dest_alloc.extra,
             (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 255dd1eba..b39b219b4 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -13,9 +13,9 @@ use rustc_middle::{mir, ty};
 use rustc_target::abi::{self, Abi, HasDataLayout, Size};
 
 use super::{
-    alloc_range, from_known_layout, mir_assign_valid_types, AllocId, Frame, InterpCx, InterpResult,
-    MPlaceTy, Machine, MemPlace, MemPlaceMeta, OffsetMode, PlaceTy, Pointer, Projectable,
-    Provenance, Scalar,
+    alloc_range, from_known_layout, mir_assign_valid_types, CtfeProvenance, Frame, InterpCx,
+    InterpResult, MPlaceTy, Machine, MemPlace, MemPlaceMeta, OffsetMode, PlaceTy, Pointer,
+    Projectable, Provenance, Scalar,
 };
 
 /// An `Immediate` represents a single immediate self-contained Rust value.
@@ -26,7 +26,7 @@ use super::{
 /// In particular, thanks to `ScalarPair`, arithmetic operations and casts can be entirely
 /// defined on `Immediate`, and do not have to work with a `Place`.
 #[derive(Copy, Clone, Debug)]
-pub enum Immediate<Prov: Provenance = AllocId> {
+pub enum Immediate<Prov: Provenance = CtfeProvenance> {
     /// A single scalar value (must have *initialized* `Scalar` ABI).
     Scalar(Scalar<Prov>),
     /// A pair of two scalar value (must have `ScalarPair` ABI where both fields are
@@ -93,12 +93,23 @@ impl<Prov: Provenance> Immediate<Prov> {
             Immediate::Uninit => bug!("Got uninit where a scalar pair was expected"),
         }
     }
+
+    /// Returns the scalar from the first component and optionally the 2nd component as metadata.
+    #[inline]
+    #[cfg_attr(debug_assertions, track_caller)] // only in debug builds due to perf (see #98980)
+    pub fn to_scalar_and_meta(self) -> (Scalar<Prov>, MemPlaceMeta<Prov>) {
+        match self {
+            Immediate::ScalarPair(val1, val2) => (val1, MemPlaceMeta::Meta(val2)),
+            Immediate::Scalar(val) => (val, MemPlaceMeta::None),
+            Immediate::Uninit => bug!("Got uninit where a scalar or scalar pair was expected"),
+        }
+    }
 }
 
 // ScalarPair needs a type to interpret, so we often have an immediate and a type together
 // as input for binary and cast operations.
 #[derive(Clone)]
-pub struct ImmTy<'tcx, Prov: Provenance = AllocId> {
+pub struct ImmTy<'tcx, Prov: Provenance = CtfeProvenance> {
     imm: Immediate<Prov>,
     pub layout: TyAndLayout<'tcx>,
 }
@@ -334,13 +345,13 @@ impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for ImmTy<'tcx, Prov> {
 /// or still in memory. The latter is an optimization, to delay reading that chunk of
 /// memory and to avoid having to store arbitrary-sized data here.
 #[derive(Copy, Clone, Debug)]
-pub(super) enum Operand<Prov: Provenance = AllocId> {
+pub(super) enum Operand<Prov: Provenance = CtfeProvenance> {
     Immediate(Immediate<Prov>),
     Indirect(MemPlace<Prov>),
 }
 
 #[derive(Clone)]
-pub struct OpTy<'tcx, Prov: Provenance = AllocId> {
+pub struct OpTy<'tcx, Prov: Provenance = CtfeProvenance> {
     op: Operand<Prov>, // Keep this private; it helps enforce invariants.
     pub layout: TyAndLayout<'tcx>,
 }
@@ -750,17 +761,19 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let layout = from_known_layout(self.tcx, self.param_env, layout, || self.layout_of(ty))?;
         let imm = match val_val {
             mir::ConstValue::Indirect { alloc_id, offset } => {
-                // We rely on mutability being set correctly in that allocation to prevent writes
-                // where none should happen.
-                let ptr = self.global_base_pointer(Pointer::new(alloc_id, offset))?;
+                // This is const data, no mutation allowed.
+                let ptr = self.global_base_pointer(Pointer::new(
+                    CtfeProvenance::from(alloc_id).as_immutable(),
+                    offset,
+                ))?;
                 return Ok(self.ptr_to_mplace(ptr.into(), layout).into());
             }
             mir::ConstValue::Scalar(x) => adjust_scalar(x)?.into(),
             mir::ConstValue::ZeroSized => Immediate::Uninit,
             mir::ConstValue::Slice { data, meta } => {
-                // We rely on mutability being set correctly in `data` to prevent writes
-                // where none should happen.
-                let ptr = Pointer::new(self.tcx.reserve_and_set_memory_alloc(data), Size::ZERO);
+                // This is const data, no mutation allowed.
+                let alloc_id = self.tcx.reserve_and_set_memory_alloc(data);
+                let ptr = Pointer::new(CtfeProvenance::from(alloc_id).as_immutable(), Size::ZERO);
                 Immediate::new_slice(self.global_base_pointer(ptr)?.into(), meta, self)
             }
         };
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index a3ba9530f..eef154257 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -20,7 +20,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         right: &ImmTy<'tcx, M::Provenance>,
         dest: &PlaceTy<'tcx, M::Provenance>,
     ) -> InterpResult<'tcx> {
-        let (val, overflowed) = self.overflowing_binary_op(op, &left, &right)?;
+        let (val, overflowed) = self.overflowing_binary_op(op, left, right)?;
         debug_assert_eq!(
             Ty::new_tup(self.tcx.tcx, &[val.layout.ty, self.tcx.types.bool]),
             dest.layout.ty,
@@ -114,9 +114,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         use rustc_middle::mir::BinOp::*;
 
         // Performs appropriate non-deterministic adjustments of NaN results.
-        let adjust_nan = |f: F| -> F {
-            if f.is_nan() { M::generate_nan(self, &[l, r]) } else { f }
-        };
+        let adjust_nan =
+            |f: F| -> F { if f.is_nan() { M::generate_nan(self, &[l, r]) } else { f } };
 
         let val = match bin_op {
             Eq => ImmTy::from_bool(l == r, *self.tcx),
@@ -157,41 +156,35 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         // Shift ops can have an RHS with a different numeric type.
         if matches!(bin_op, Shl | ShlUnchecked | Shr | ShrUnchecked) {
-            let size = u128::from(left_layout.size.bits());
-            // Even if `r` is signed, we treat it as if it was unsigned (i.e., we use its
-            // zero-extended form). This matches the codegen backend:
-            // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/base.rs#L315-L317>.
-            // The overflow check is also ignorant to the sign:
-            // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/mir/rvalue.rs#L728>.
-            // This would behave rather strangely if we had integer types of size 256: a shift by
-            // -1i8 would actually shift by 255, but that would *not* be considered overflowing. A
-            // shift by -1i16 though would be considered overflowing. If we had integers of size
-            // 512, then a shift by -1i8 would even produce a different result than one by -1i16:
-            // the first shifts by 255, the latter by u16::MAX % 512 = 511. Lucky enough, our
-            // integers are maximally 128bits wide, so negative shifts *always* overflow and we have
-            // consistent results for the same value represented at different bit widths.
-            assert!(size <= 128);
-            let original_r = r;
-            let overflow = r >= size;
-            // The shift offset is implicitly masked to the type size, to make sure this operation
-            // is always defined. This is the one MIR operator that does *not* directly map to a
-            // single LLVM operation. See
-            // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/common.rs#L131-L158>
-            // for the corresponding truncation in our codegen backends.
-            let r = r % size;
-            let r = u32::try_from(r).unwrap(); // we masked so this will always fit
+            let size = left_layout.size.bits();
+            // The shift offset is implicitly masked to the type size. (This is the one MIR operator
+            // that does *not* directly map to a single LLVM operation.) Compute how much we
+            // actually shift and whether there was an overflow due to shifting too much.
+            let (shift_amount, overflow) = if right_layout.abi.is_signed() {
+                let shift_amount = self.sign_extend(r, right_layout) as i128;
+                let overflow = shift_amount < 0 || shift_amount >= i128::from(size);
+                let masked_amount = (shift_amount as u128) % u128::from(size);
+                debug_assert_eq!(overflow, shift_amount != (masked_amount as i128));
+                (masked_amount, overflow)
+            } else {
+                let shift_amount = r;
+                let masked_amount = shift_amount % u128::from(size);
+                (masked_amount, shift_amount != masked_amount)
+            };
+            let shift_amount = u32::try_from(shift_amount).unwrap(); // we masked so this will always fit
+            // Compute the shifted result.
             let result = if left_layout.abi.is_signed() {
                 let l = self.sign_extend(l, left_layout) as i128;
                 let result = match bin_op {
-                    Shl | ShlUnchecked => l.checked_shl(r).unwrap(),
-                    Shr | ShrUnchecked => l.checked_shr(r).unwrap(),
+                    Shl | ShlUnchecked => l.checked_shl(shift_amount).unwrap(),
+                    Shr | ShrUnchecked => l.checked_shr(shift_amount).unwrap(),
                     _ => bug!(),
                 };
                 result as u128
             } else {
                 match bin_op {
-                    Shl | ShlUnchecked => l.checked_shl(r).unwrap(),
-                    Shr | ShrUnchecked => l.checked_shr(r).unwrap(),
+                    Shl | ShlUnchecked => l.checked_shl(shift_amount).unwrap(),
+                    Shr | ShrUnchecked => l.checked_shr(shift_amount).unwrap(),
                     _ => bug!(),
                 }
             };
@@ -200,7 +193,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             if overflow && let Some(intrinsic_name) = throw_ub_on_overflow {
                 throw_ub_custom!(
                     fluent::const_eval_overflow_shift,
-                    val = original_r,
+                    val = if right_layout.abi.is_signed() {
+                        (self.sign_extend(r, right_layout) as i128).to_string()
+                    } else {
+                        r.to_string()
+                    },
                     name = intrinsic_name
                 );
             }
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index 09ffdec7d..639b269ac 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -7,22 +7,21 @@ use std::assert_matches::assert_matches;
 use either::{Either, Left, Right};
 
 use rustc_ast::Mutability;
-use rustc_index::IndexSlice;
 use rustc_middle::mir;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::Ty;
-use rustc_target::abi::{Abi, Align, FieldIdx, HasDataLayout, Size, FIRST_VARIANT};
+use rustc_target::abi::{Abi, Align, HasDataLayout, Size};
 
 use super::{
-    alloc_range, mir_assign_valid_types, AllocId, AllocRef, AllocRefMut, CheckAlignMsg, ImmTy,
-    Immediate, InterpCx, InterpResult, Machine, MemoryKind, Misalignment, OffsetMode, OpTy,
+    alloc_range, mir_assign_valid_types, AllocRef, AllocRefMut, CheckAlignMsg, CtfeProvenance,
+    ImmTy, Immediate, InterpCx, InterpResult, Machine, MemoryKind, Misalignment, OffsetMode, OpTy,
     Operand, Pointer, PointerArithmetic, Projectable, Provenance, Readable, Scalar,
 };
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
 /// Information required for the sound usage of a `MemPlace`.
-pub enum MemPlaceMeta<Prov: Provenance = AllocId> {
+pub enum MemPlaceMeta<Prov: Provenance = CtfeProvenance> {
     /// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
     Meta(Scalar<Prov>),
     /// `Sized` types or unsized `extern type`
@@ -50,7 +49,7 @@ impl<Prov: Provenance> MemPlaceMeta<Prov> {
 }
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
-pub(super) struct MemPlace<Prov: Provenance = AllocId> {
+pub(super) struct MemPlace<Prov: Provenance = CtfeProvenance> {
     /// The pointer can be a pure integer, with the `None` provenance.
     pub ptr: Pointer<Option<Prov>>,
     /// Metadata for unsized places. Interpretation is up to the type.
@@ -101,7 +100,7 @@ impl<Prov: Provenance> MemPlace<Prov> {
 
 /// A MemPlace with its layout. Constructing it is only possible in this module.
 #[derive(Clone, Hash, Eq, PartialEq)]
-pub struct MPlaceTy<'tcx, Prov: Provenance = AllocId> {
+pub struct MPlaceTy<'tcx, Prov: Provenance = CtfeProvenance> {
     mplace: MemPlace<Prov>,
     pub layout: TyAndLayout<'tcx>,
 }
@@ -180,7 +179,7 @@ impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for MPlaceTy<'tcx, Prov> {
 }
 
 #[derive(Copy, Clone, Debug)]
-pub(super) enum Place<Prov: Provenance = AllocId> {
+pub(super) enum Place<Prov: Provenance = CtfeProvenance> {
     /// A place referring to a value allocated in the `Memory` system.
     Ptr(MemPlace<Prov>),
 
@@ -196,7 +195,7 @@ pub(super) enum Place<Prov: Provenance = AllocId> {
 }
 
 #[derive(Clone)]
-pub struct PlaceTy<'tcx, Prov: Provenance = AllocId> {
+pub struct PlaceTy<'tcx, Prov: Provenance = CtfeProvenance> {
     place: Place<Prov>, // Keep this private; it helps enforce invariants.
     pub layout: TyAndLayout<'tcx>,
 }
@@ -407,11 +406,7 @@ where
         let pointee_type =
             val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty;
         let layout = self.layout_of(pointee_type)?;
-        let (ptr, meta) = match **val {
-            Immediate::Scalar(ptr) => (ptr, MemPlaceMeta::None),
-            Immediate::ScalarPair(ptr, meta) => (ptr, MemPlaceMeta::Meta(meta)),
-            Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
-        };
+        let (ptr, meta) = val.to_scalar_and_meta();
 
         // `ref_to_mplace` is called on raw pointers even if they don't actually get dereferenced;
         // we hence can't call `size_and_align_of` since that asserts more validity than we want.
@@ -456,7 +451,7 @@ 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_mplace(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.
@@ -472,7 +467,7 @@ 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_mplace(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.
@@ -977,34 +972,6 @@ where
         Ok(self.ptr_with_meta_to_mplace(ptr.into(), MemPlaceMeta::Meta(meta), layout))
     }
 
-    /// Writes the aggregate to the destination.
-    #[instrument(skip(self), level = "trace")]
-    pub fn write_aggregate(
-        &mut self,
-        kind: &mir::AggregateKind<'tcx>,
-        operands: &IndexSlice<FieldIdx, mir::Operand<'tcx>>,
-        dest: &PlaceTy<'tcx, M::Provenance>,
-    ) -> InterpResult<'tcx> {
-        self.write_uninit(dest)?;
-        let (variant_index, variant_dest, active_field_index) = match *kind {
-            mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
-                let variant_dest = self.project_downcast(dest, variant_index)?;
-                (variant_index, variant_dest, active_field_index)
-            }
-            _ => (FIRST_VARIANT, dest.clone(), None),
-        };
-        if active_field_index.is_some() {
-            assert_eq!(operands.len(), 1);
-        }
-        for (field_index, operand) in operands.iter_enumerated() {
-            let field_index = active_field_index.unwrap_or(field_index);
-            let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
-            let op = self.eval_operand(operand, Some(field_dest.layout))?;
-            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
-        }
-        self.write_discriminant(variant_index, dest)
-    }
-
     pub fn raw_const_to_mplace(
         &self,
         raw: mir::ConstAlloc<'tcx>,
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index 6694c43c9..9a034ba22 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -163,13 +163,26 @@ where
             // 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)? {
-                Some((_, align)) => (base_meta, offset.align_to(align)),
-                None => {
-                    // For unsized types with an extern type tail we perform no adjustments.
-                    // NOTE: keep this in sync with `PlaceRef::project_field` in the codegen backend.
-                    assert!(matches!(base_meta, MemPlaceMeta::None));
+                Some((_, align)) => {
+                    // For packed types, we need to cap alignment.
+                    let align = if let ty::Adt(def, _) = base.layout().ty.kind()
+                        && let Some(packed) = def.repr().pack
+                    {
+                        align.min(packed)
+                    } else {
+                        align
+                    };
+                    (base_meta, offset.align_to(align))
+                }
+                None if offset == Size::ZERO => {
+                    // If the offset is 0, then rounding it up to alignment wouldn't change anything,
+                    // so we can do this even for types where we cannot determine the alignment.
                     (base_meta, offset)
                 }
+                None => {
+                    // We don't know the alignment of this field, so we cannot adjust.
+                    throw_unsup_format!("`extern type` does not have a known offset")
+                }
             }
         } else {
             // base_meta could be present; we might be accessing a sized field of an unsized
@@ -195,6 +208,24 @@ where
         if layout.abi.is_uninhabited() {
             // `read_discriminant` should have excluded uninhabited variants... but ConstProp calls
             // us on dead code.
+            // In the future we might want to allow this to permit code like this:
+            // (this is a Rust/MIR pseudocode mix)
+            // ```
+            // enum Option2 {
+            //   Some(i32, !),
+            //   None,
+            // }
+            //
+            // fn panic() -> ! { panic!() }
+            //
+            // let x: Option2;
+            // x.Some.0 = 42;
+            // x.Some.1 = panic();
+            // SetDiscriminant(x, Some);
+            // ```
+            // However, for now we don't generate such MIR, and this check here *has* found real
+            // bugs (see https://github.com/rust-lang/rust/issues/115145), so we will keep rejecting
+            // it.
             throw_inval!(ConstPropNonsense)
         }
         // This cannot be `transmute` as variants *can* have a smaller size than the entire enum.
@@ -256,13 +287,13 @@ where
     }
 
     /// Iterates over all fields of an array. Much more efficient than doing the
-    /// same by repeatedly calling `operand_index`.
+    /// same by repeatedly calling `project_index`.
     pub fn project_array_fields<'a, P: Projectable<'tcx, M::Provenance>>(
         &self,
         base: &'a P,
     ) -> InterpResult<'tcx, ArrayIterator<'tcx, 'a, M::Provenance, P>> {
         let abi::FieldsShape::Array { stride, .. } = base.layout().fields else {
-            span_bug!(self.cur_span(), "operand_array_fields: expected an array layout");
+            span_bug!(self.cur_span(), "project_array_fields: expected an array layout");
         };
         let len = base.len(self)?;
         let field_layout = base.layout().field(self, 0);
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index b6993d939..d48329b6c 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -4,11 +4,12 @@
 
 use either::Either;
 
+use rustc_index::IndexSlice;
 use rustc_middle::mir;
-use rustc_middle::mir::interpret::{InterpResult, Scalar};
 use rustc_middle::ty::layout::LayoutOf;
+use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
 
-use super::{ImmTy, InterpCx, Machine, Projectable};
+use super::{ImmTy, InterpCx, InterpResult, Machine, PlaceTy, Projectable, Scalar};
 use crate::util;
 
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
@@ -187,34 +188,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
 
             Repeat(ref operand, _) => {
-                let src = self.eval_operand(operand, None)?;
-                assert!(src.layout.is_sized());
-                let dest = self.force_allocation(&dest)?;
-                let length = dest.len(self)?;
-
-                if length == 0 {
-                    // Nothing to copy... but let's still make sure that `dest` as a place is valid.
-                    self.get_place_alloc_mut(&dest)?;
-                } else {
-                    // Write the src to the first element.
-                    let first = self.project_index(&dest, 0)?;
-                    self.copy_op(&src, &first, /*allow_transmute*/ false)?;
-
-                    // This is performance-sensitive code for big static/const arrays! So we
-                    // avoid writing each operand individually and instead just make many copies
-                    // of the first element.
-                    let elem_size = first.layout.size;
-                    let first_ptr = first.ptr();
-                    let rest_ptr = first_ptr.offset(elem_size, self)?;
-                    // No alignment requirement since `copy_op` above already checked it.
-                    self.mem_copy_repeatedly(
-                        first_ptr,
-                        rest_ptr,
-                        elem_size,
-                        length - 1,
-                        /*nonoverlapping:*/ true,
-                    )?;
-                }
+                self.write_repeat(operand, &dest)?;
             }
 
             Len(place) => {
@@ -307,6 +281,73 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         Ok(())
     }
 
+    /// Writes the aggregate to the destination.
+    #[instrument(skip(self), level = "trace")]
+    fn write_aggregate(
+        &mut self,
+        kind: &mir::AggregateKind<'tcx>,
+        operands: &IndexSlice<FieldIdx, mir::Operand<'tcx>>,
+        dest: &PlaceTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
+        self.write_uninit(dest)?; // make sure all the padding ends up as uninit
+        let (variant_index, variant_dest, active_field_index) = match *kind {
+            mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
+                let variant_dest = self.project_downcast(dest, variant_index)?;
+                (variant_index, variant_dest, active_field_index)
+            }
+            _ => (FIRST_VARIANT, dest.clone(), None),
+        };
+        if active_field_index.is_some() {
+            assert_eq!(operands.len(), 1);
+        }
+        for (field_index, operand) in operands.iter_enumerated() {
+            let field_index = active_field_index.unwrap_or(field_index);
+            let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
+            let op = self.eval_operand(operand, Some(field_dest.layout))?;
+            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
+        }
+        self.write_discriminant(variant_index, dest)
+    }
+
+    /// Repeats `operand` into the destination. `dest` must have array type, and that type
+    /// determines how often `operand` is repeated.
+    fn write_repeat(
+        &mut self,
+        operand: &mir::Operand<'tcx>,
+        dest: &PlaceTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
+        let src = self.eval_operand(operand, None)?;
+        assert!(src.layout.is_sized());
+        let dest = self.force_allocation(&dest)?;
+        let length = dest.len(self)?;
+
+        if length == 0 {
+            // Nothing to copy... but let's still make sure that `dest` as a place is valid.
+            self.get_place_alloc_mut(&dest)?;
+        } else {
+            // Write the src to the first element.
+            let first = self.project_index(&dest, 0)?;
+            self.copy_op(&src, &first, /*allow_transmute*/ false)?;
+
+            // This is performance-sensitive code for big static/const arrays! So we
+            // avoid writing each operand individually and instead just make many copies
+            // of the first element.
+            let elem_size = first.layout.size;
+            let first_ptr = first.ptr();
+            let rest_ptr = first_ptr.offset(elem_size, self)?;
+            // No alignment requirement since `copy_op` above already checked it.
+            self.mem_copy_repeatedly(
+                first_ptr,
+                rest_ptr,
+                elem_size,
+                length - 1,
+                /*nonoverlapping:*/ true,
+            )?;
+        }
+
+        Ok(())
+    }
+
     /// Evaluate the given terminator. Will also adjust the stack frame and statement position accordingly.
     fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> InterpResult<'tcx> {
         info!("{:?}", terminator.kind);
diff --git a/compiler/rustc_const_eval/src/interpret/terminator.rs b/compiler/rustc_const_eval/src/interpret/terminator.rs
index b54c66814..2358caffc 100644
--- a/compiler/rustc_const_eval/src/interpret/terminator.rs
+++ b/compiler/rustc_const_eval/src/interpret/terminator.rs
@@ -18,14 +18,14 @@ use rustc_target::abi::{
 use rustc_target::spec::abi::Abi;
 
 use super::{
-    AllocId, FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy, Projectable,
-    Provenance, Scalar, StackPopCleanup,
+    CtfeProvenance, FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy,
+    Projectable, Provenance, Scalar, StackPopCleanup,
 };
 use crate::fluent_generated as fluent;
 
 /// An argment passed to a function.
 #[derive(Clone, Debug)]
-pub enum FnArg<'tcx, Prov: Provenance = AllocId> {
+pub enum FnArg<'tcx, Prov: Provenance = CtfeProvenance> {
     /// Pass a copy of the given operand.
     Copy(OpTy<'tcx, Prov>),
     /// Allow for the argument to be passed in-place: destroy the value originally stored at that place and
@@ -51,7 +51,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
         match arg {
             FnArg::Copy(op) => Ok(op.clone()),
-            FnArg::InPlace(place) => self.place_to_op(&place),
+            FnArg::InPlace(place) => self.place_to_op(place),
         }
     }
 
@@ -384,10 +384,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
 
         // Compatible integer types (in particular, usize vs ptr-sized-u32/u64).
+        // `char` counts as `u32.`
         let int_ty = |ty: Ty<'tcx>| {
             Some(match ty.kind() {
                 ty::Int(ity) => (Integer::from_int_ty(&self.tcx, *ity), /* signed */ true),
                 ty::Uint(uty) => (Integer::from_uint_ty(&self.tcx, *uty), /* signed */ false),
+                ty::Char => (Integer::I32, /* signed */ false),
                 _ => return None,
             })
         };
@@ -410,7 +412,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // so we implement a type-based check that reflects the guaranteed rules for ABI compatibility.
         if self.layout_compat(caller_abi.layout, callee_abi.layout)? {
             // Ensure that our checks imply actual ABI compatibility for this concrete call.
-            assert!(caller_abi.eq_abi(&callee_abi));
+            assert!(caller_abi.eq_abi(callee_abi));
             return Ok(true);
         } else {
             trace!(
@@ -464,7 +466,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // We work with a copy of the argument for now; if this is in-place argument passing, we
         // will later protect the source it comes from. This means the callee cannot observe if we
         // did in-place of by-copy argument passing, except for pointer equality tests.
-        let caller_arg_copy = self.copy_fn_arg(&caller_arg)?;
+        let caller_arg_copy = self.copy_fn_arg(caller_arg)?;
         if !already_live {
             let local = callee_arg.as_local().unwrap();
             let meta = caller_arg_copy.meta();
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index d21fef58f..07500f744 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -227,7 +227,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         // Sometimes the index is beyond the number of upvars (seen
                         // for a coroutine).
                         let var_hir_id = captured_place.get_root_variable();
-                        let node = self.ecx.tcx.hir().get(var_hir_id);
+                        let node = self.ecx.tcx.hir_node(var_hir_id);
                         if let hir::Node::Pat(pat) = node {
                             if let hir::PatKind::Binding(_, _, ident, _) = pat.kind {
                                 name = Some(ident.name);
@@ -896,7 +896,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let mut visitor = ValidityVisitor { path, ref_tracking, ctfe_mode, ecx: self };
 
         // Run it.
-        match visitor.visit_value(&op) {
+        match visitor.visit_value(op) {
             Ok(()) => Ok(()),
             // Pass through validation failures and "invalid program" issues.
             Err(err)
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index fc21ad1f1..de0590a4b 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -21,7 +21,7 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
     /// `read_discriminant` can be hooked for better error messages.
     #[inline(always)]
     fn read_discriminant(&mut self, v: &Self::V) -> InterpResult<'tcx, VariantIdx> {
-        Ok(self.ecx().read_discriminant(&v.to_op(self.ecx())?)?)
+        self.ecx().read_discriminant(&v.to_op(self.ecx())?)
     }
 
     /// This function provides the chance to reorder the order in which fields are visited for
@@ -97,14 +97,14 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
                 let inner_mplace = self.ecx().unpack_dyn_trait(&dest)?.0;
                 trace!("walk_value: dyn object layout: {:#?}", inner_mplace.layout);
                 // recurse with the inner type
-                return self.visit_field(&v, 0, &inner_mplace.into());
+                return self.visit_field(v, 0, &inner_mplace.into());
             }
             ty::Dynamic(_, _, ty::DynStar) => {
                 // DynStar types. Very different from a dyn type (but strangely part of the
                 // same variant in `TyKind`): These are pairs where the 2nd component is the
                 // vtable, and the first component is the data (which must be ptr-sized).
                 let data = self.ecx().unpack_dyn_star(v)?.0;
-                return self.visit_field(&v, 0, &data);
+                return self.visit_field(v, 0, &data);
             }
             // Slices do not need special handling here: they have `Array` field
             // placement with length 0, so we enter the `Array` case below which
diff --git a/compiler/rustc_const_eval/src/lib.rs b/compiler/rustc_const_eval/src/lib.rs
index 1e21c4940..d6c36ccc5 100644
--- a/compiler/rustc_const_eval/src/lib.rs
+++ b/compiler/rustc_const_eval/src/lib.rs
@@ -4,9 +4,9 @@ Rust MIR: a lowered representation of Rust.
 
 */
 
-#![cfg_attr(not(bootstrap), allow(internal_features))]
-#![cfg_attr(not(bootstrap), feature(rustdoc_internals))]
-#![cfg_attr(not(bootstrap), doc(rust_logo))]
+#![allow(internal_features)]
+#![feature(rustdoc_internals)]
+#![doc(rust_logo)]
 #![deny(rustc::untranslatable_diagnostic)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
@@ -39,11 +39,9 @@ pub mod util;
 
 pub use errors::ReportErrorExt;
 
-use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
-use rustc_fluent_macro::fluent_messages;
 use rustc_middle::{ty, util::Providers};
 
-fluent_messages! { "../messages.ftl" }
+rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 pub fn provide(providers: &mut Providers) {
     const_eval::provide(providers);
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index 76116e339..949606ed6 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -12,7 +12,7 @@ use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, InstanceDef, Ty, TyCtxt};
 use rustc_middle::ty::{TraitRef, TypeVisitableExt};
-use rustc_mir_dataflow::{self, Analysis};
+use rustc_mir_dataflow::Analysis;
 use rustc_span::{sym, Span, Symbol};
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
 use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt, SelectionContext};
@@ -22,7 +22,7 @@ use std::mem;
 use std::ops::{ControlFlow, Deref};
 
 use super::ops::{self, NonConstOp, Status};
-use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop};
+use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
 use super::resolver::FlowSensitiveAnalysis;
 use super::{ConstCx, Qualif};
 use crate::const_eval::is_unstable_const_fn;
@@ -35,7 +35,7 @@ type QualifResults<'mir, 'tcx, Q> =
 pub struct Qualifs<'mir, 'tcx> {
     has_mut_interior: Option<QualifResults<'mir, 'tcx, HasMutInterior>>,
     needs_drop: Option<QualifResults<'mir, 'tcx, NeedsDrop>>,
-    // needs_non_const_drop: Option<QualifResults<'mir, 'tcx, NeedsNonConstDrop>>,
+    needs_non_const_drop: Option<QualifResults<'mir, 'tcx, NeedsNonConstDrop>>,
 }
 
 impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
@@ -60,9 +60,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
             let ConstCx { tcx, body, .. } = *ccx;
 
             FlowSensitiveAnalysis::new(NeedsDrop, ccx)
-                .into_engine(tcx, &body)
+                .into_engine(tcx, body)
                 .iterate_to_fixpoint()
-                .into_results_cursor(&body)
+                .into_results_cursor(body)
         });
 
         needs_drop.seek_before_primary_effect(location);
@@ -78,27 +78,25 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
         local: Local,
         location: Location,
     ) -> bool {
-        // FIXME(effects) replace with `NeedsNonconstDrop` after const traits work again
-        /*
         let ty = ccx.body.local_decls[local].ty;
-        if !NeedsDrop::in_any_value_of_ty(ccx, ty) {
+        // Peeking into opaque types causes cycles if the current function declares said opaque
+        // type. Thus we avoid short circuiting on the type and instead run the more expensive
+        // analysis that looks at the actual usage within this function
+        if !ty.has_opaque_types() && !NeedsNonConstDrop::in_any_value_of_ty(ccx, ty) {
             return false;
         }
 
         let needs_non_const_drop = self.needs_non_const_drop.get_or_insert_with(|| {
             let ConstCx { tcx, body, .. } = *ccx;
 
-            FlowSensitiveAnalysis::new(NeedsDrop, ccx)
-                .into_engine(tcx, &body)
+            FlowSensitiveAnalysis::new(NeedsNonConstDrop, ccx)
+                .into_engine(tcx, body)
                 .iterate_to_fixpoint()
-                .into_results_cursor(&body)
+                .into_results_cursor(body)
         });
 
         needs_non_const_drop.seek_before_primary_effect(location);
         needs_non_const_drop.get().contains(local)
-        */
-
-        self.needs_drop(ccx, local, location)
     }
 
     /// Returns `true` if `local` is `HasMutInterior` at the given `Location`.
@@ -122,9 +120,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
             let ConstCx { tcx, body, .. } = *ccx;
 
             FlowSensitiveAnalysis::new(HasMutInterior, ccx)
-                .into_engine(tcx, &body)
+                .into_engine(tcx, body)
                 .iterate_to_fixpoint()
-                .into_results_cursor(&body)
+                .into_results_cursor(body)
         });
 
         has_mut_interior.seek_before_primary_effect(location);
@@ -170,9 +168,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
 
             hir::ConstContext::Const { .. } | hir::ConstContext::Static(_) => {
                 let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx)
-                    .into_engine(ccx.tcx, &ccx.body)
+                    .into_engine(ccx.tcx, ccx.body)
                     .iterate_to_fixpoint()
-                    .into_results_cursor(&ccx.body);
+                    .into_results_cursor(ccx.body);
 
                 cursor.seek_after_primary_effect(return_loc);
                 cursor.get().contains(RETURN_PLACE)
@@ -225,7 +223,7 @@ impl<'mir, 'tcx> Deref for Checker<'mir, 'tcx> {
     type Target = ConstCx<'mir, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 
@@ -248,7 +246,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         // `async` functions cannot be `const fn`. This is checked during AST lowering, so there's
         // no need to emit duplicate errors here.
         if self.ccx.is_async() || body.coroutine.is_some() {
-            tcx.sess.delay_span_bug(body.span, "`async` functions cannot be `const fn`");
+            tcx.sess.span_delayed_bug(body.span, "`async` functions cannot be `const fn`");
             return;
         }
 
@@ -272,15 +270,15 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         }
 
         if !tcx.has_attr(def_id, sym::rustc_do_not_const_check) {
-            self.visit_body(&body);
+            self.visit_body(body);
         }
 
         // If we got through const-checking without emitting any "primary" errors, emit any
         // "secondary" errors if they occurred.
         let secondary_errors = mem::take(&mut self.secondary_errors);
         if self.error_emitted.is_none() {
-            for mut error in secondary_errors {
-                self.tcx.sess.diagnostic().emit_diagnostic(&mut error);
+            for error in secondary_errors {
+                self.tcx.sess.dcx().emit_diagnostic(error);
             }
         } else {
             assert!(self.tcx.sess.has_errors().is_some());
@@ -357,7 +355,9 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
 
     fn check_static(&mut self, def_id: DefId, span: Span) {
         if self.tcx.is_thread_local_static(def_id) {
-            self.tcx.sess.delay_span_bug(span, "tls access is checked in `Rvalue::ThreadLocalRef`");
+            self.tcx
+                .sess
+                .span_delayed_bug(span, "tls access is checked in `Rvalue::ThreadLocalRef`");
         }
         self.check_op_spanned(ops::StaticAccess, span)
     }
@@ -503,7 +503,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Fake, place)
             | Rvalue::AddressOf(Mutability::Not, place) => {
                 let borrowed_place_has_mut_interior = qualifs::in_place::<HasMutInterior, _>(
-                    &self.ccx,
+                    self.ccx,
                     &mut |local| self.qualifs.has_mut_interior(self.ccx, local, location),
                     place.as_ref(),
                 );
@@ -1011,9 +1011,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 let mut err_span = self.span;
                 let ty_of_dropped_place = dropped_place.ty(self.body, self.tcx).ty;
 
-                // FIXME(effects) replace with `NeedsNonConstDrop` once we fix const traits
                 let ty_needs_non_const_drop =
-                    qualifs::NeedsDrop::in_any_value_of_ty(self.ccx, ty_of_dropped_place);
+                    qualifs::NeedsNonConstDrop::in_any_value_of_ty(self.ccx, ty_of_dropped_place);
 
                 debug!(?ty_of_dropped_place, ?ty_needs_non_const_drop);
 
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/mod.rs b/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
index e51082e1e..4f7e165c5 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
@@ -82,8 +82,8 @@ pub fn rustc_allow_const_fn_unstable(
     def_id: LocalDefId,
     feature_gate: Symbol,
 ) -> bool {
-    let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(def_id));
-    attr::rustc_allow_const_fn_unstable(&tcx.sess, attrs).any(|name| name == feature_gate)
+    let attrs = tcx.hir().attrs(tcx.local_def_id_to_hir_id(def_id));
+    attr::rustc_allow_const_fn_unstable(tcx.sess, attrs).any(|name| name == feature_gate)
 }
 
 /// Returns `true` if the given `const fn` is "const-stable".
@@ -112,7 +112,7 @@ pub fn is_const_stable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
         None if is_parent_const_stable_trait(tcx, def_id) => {
             // Remove this when `#![feature(const_trait_impl)]` is stabilized,
             // returning `true` unconditionally.
-            tcx.sess.delay_span_bug(
+            tcx.sess.span_delayed_bug(
                 tcx.def_span(def_id),
                 "trait implementations cannot be const stable yet",
             );
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
index 40183bacc..2de6362b9 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
@@ -119,8 +119,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
             match self_ty.kind() {
                 Param(param_ty) => {
                     debug!(?param_ty);
-                    let caller_hir_id = tcx.hir().local_def_id_to_hir_id(caller);
-                    if let Some(generics) = tcx.hir().get(caller_hir_id).generics() {
+                    if let Some(generics) = tcx.hir_node_by_def_id(caller).generics() {
                         let constraint = with_no_trimmed_paths!(format!(
                             "~const {}",
                             trait_ref.print_only_trait_path()
@@ -129,7 +128,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                             tcx,
                             generics,
                             err,
-                            &param_ty.name.as_str(),
+                            param_ty.name.as_str(),
                             &constraint,
                             None,
                             None,
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs b/compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs
index aff256b3e..5cd13783c 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs
@@ -5,7 +5,7 @@ use rustc_span::{symbol::sym, Span};
 
 use super::check::Qualifs;
 use super::ops::{self, NonConstOp};
-use super::qualifs::{NeedsDrop, Qualif};
+use super::qualifs::{NeedsNonConstDrop, Qualif};
 use super::ConstCx;
 
 /// Returns `true` if we should use the more precise live drop checker that runs after drop
@@ -54,7 +54,7 @@ impl<'mir, 'tcx> std::ops::Deref for CheckLiveDrops<'mir, 'tcx> {
     type Target = ConstCx<'mir, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 
@@ -83,8 +83,7 @@ impl<'tcx> Visitor<'tcx> for CheckLiveDrops<'_, 'tcx> {
             mir::TerminatorKind::Drop { place: dropped_place, .. } => {
                 let dropped_ty = dropped_place.ty(self.body, self.tcx).ty;
 
-                // FIXME(effects) use `NeedsNonConstDrop`
-                if !NeedsDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
+                if !NeedsNonConstDrop::in_any_value_of_ty(self.ccx, dropped_ty) {
                     // Instead of throwing a bug, we just return here. This is because we have to
                     // run custom `const Drop` impls.
                     return;
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
index de3186a53..7e1cbfe66 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
@@ -23,8 +23,7 @@ pub fn in_any_value_of_ty<'tcx>(
     ConstQualifs {
         has_mut_interior: HasMutInterior::in_any_value_of_ty(cx, ty),
         needs_drop: NeedsDrop::in_any_value_of_ty(cx, ty),
-        // FIXME(effects)
-        needs_non_const_drop: NeedsDrop::in_any_value_of_ty(cx, ty),
+        needs_non_const_drop: NeedsNonConstDrop::in_any_value_of_ty(cx, ty),
         custom_eq: CustomEq::in_any_value_of_ty(cx, ty),
         tainted_by_errors,
     }
@@ -155,12 +154,27 @@ impl Qualif for NeedsNonConstDrop {
             return false;
         }
 
-        // FIXME(effects) constness
+        // FIXME(effects): If `destruct` is not a `const_trait`,
+        // or effects are disabled in this crate, then give up.
+        let destruct_def_id = cx.tcx.require_lang_item(LangItem::Destruct, Some(cx.body.span));
+        if cx.tcx.generics_of(destruct_def_id).host_effect_index.is_none()
+            || !cx.tcx.features().effects
+        {
+            return NeedsDrop::in_any_value_of_ty(cx, ty);
+        }
+
         let obligation = Obligation::new(
             cx.tcx,
             ObligationCause::dummy_with_span(cx.body.span),
             cx.param_env,
-            ty::TraitRef::from_lang_item(cx.tcx, LangItem::Destruct, cx.body.span, [ty]),
+            ty::TraitRef::new(
+                cx.tcx,
+                destruct_def_id,
+                [
+                    ty::GenericArg::from(ty),
+                    ty::GenericArg::from(cx.tcx.expected_host_effect_param_for_body(cx.def_id())),
+                ],
+            ),
         );
 
         let infcx = cx.tcx.infer_ctxt().build();
diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index 32af537e2..8b2ea2dc2 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -188,7 +188,7 @@ impl<'a, 'tcx> std::ops::Deref for Validator<'a, 'tcx> {
     type Target = ConstCx<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 
@@ -229,7 +229,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 let statement = &self.body[loc.block].statements[loc.statement_index];
                 match &statement.kind {
                     StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>(
-                        &self.ccx,
+                        self.ccx,
                         &mut |l| self.qualif_local::<Q>(l),
                         rhs,
                     ),
@@ -246,7 +246,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 match &terminator.kind {
                     TerminatorKind::Call { .. } => {
                         let return_ty = self.body.local_decls[local].ty;
-                        Q::in_any_value_of_ty(&self.ccx, return_ty)
+                        Q::in_any_value_of_ty(self.ccx, return_ty)
                     }
                     kind => {
                         span_bug!(terminator.source_info.span, "{:?} not promotable", kind);
@@ -864,6 +864,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
             };
 
             // Use the underlying local for this (necessarily interior) borrow.
+            debug_assert!(region.is_erased());
             let ty = local_decls[place.local].ty;
             let span = statement.source_info.span;
 
@@ -873,8 +874,6 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                 ty::TypeAndMut { ty, mutbl: borrow_kind.to_mutbl_lossy() },
             );
 
-            *region = tcx.lifetimes.re_erased;
-
             let mut projection = vec![PlaceElem::Deref];
             projection.extend(place.projection);
             place.projection = tcx.mk_place_elems(&projection);
@@ -1024,36 +1023,3 @@ pub fn promote_candidates<'tcx>(
 
     promotions
 }
-
-/// This function returns `true` if the function being called in the array
-/// repeat expression is a `const` function.
-pub fn is_const_fn_in_array_repeat_expression<'tcx>(
-    ccx: &ConstCx<'_, 'tcx>,
-    place: &Place<'tcx>,
-    body: &Body<'tcx>,
-) -> bool {
-    match place.as_local() {
-        // rule out cases such as: `let my_var = some_fn(); [my_var; N]`
-        Some(local) if body.local_decls[local].is_user_variable() => return false,
-        None => return false,
-        _ => {}
-    }
-
-    for block in body.basic_blocks.iter() {
-        if let Some(Terminator { kind: TerminatorKind::Call { func, destination, .. }, .. }) =
-            &block.terminator
-        {
-            if let Operand::Constant(box ConstOperand { const_, .. }) = func {
-                if let ty::FnDef(def_id, _) = *const_.ty().kind() {
-                    if destination == place {
-                        if ccx.tcx.is_const_fn(def_id) {
-                            return true;
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    false
-}
diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index 5922922d4..cca5b90ab 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -128,9 +128,9 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
     #[track_caller]
     fn fail(&self, location: Location, msg: impl AsRef<str>) {
         let span = self.body.source_info(location).span;
-        // We use `delay_span_bug` as we might see broken MIR when other errors have already
+        // We use `span_delayed_bug` as we might see broken MIR when other errors have already
         // occurred.
-        self.tcx.sess.diagnostic().delay_span_bug(
+        self.tcx.sess.dcx().span_delayed_bug(
             span,
             format!(
                 "broken MIR in {:?} ({}) at {:?}:\n{}",
@@ -285,6 +285,12 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
             UnwindAction::Unreachable | UnwindAction::Terminate(UnwindTerminateReason::Abi) => (),
         }
     }
+
+    fn is_critical_call_edge(&self, target: Option<BasicBlock>, unwind: UnwindAction) -> bool {
+        let Some(target) = target else { return false };
+        matches!(unwind, UnwindAction::Cleanup(_) | UnwindAction::Terminate(_))
+            && self.body.basic_blocks.predecessors()[target].len() > 1
+    }
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
@@ -425,6 +431,22 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
                 }
                 self.check_unwind_edge(location, *unwind);
 
+                // The code generation assumes that there are no critical call edges. The assumption
+                // is used to simplify inserting code that should be executed along the return edge
+                // from the call. FIXME(tmiasko): Since this is a strictly code generation concern,
+                // the code generation should be responsible for handling it.
+                if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Optimized)
+                    && self.is_critical_call_edge(*target, *unwind)
+                {
+                    self.fail(
+                        location,
+                        format!(
+                            "encountered critical edge in `Call` terminator {:?}",
+                            terminator.kind,
+                        ),
+                    );
+                }
+
                 // The call destination place and Operand::Move place used as an argument might be
                 // passed by a reference to the callee. Consequently they must be non-overlapping
                 // and cannot be packed. Currently this simply checks for duplicate places.
@@ -549,7 +571,7 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
 
     fn visit_source_scope(&mut self, scope: SourceScope) {
         if self.body.source_scopes.get(scope).is_none() {
-            self.tcx.sess.diagnostic().delay_span_bug(
+            self.tcx.sess.dcx().span_delayed_bug(
                 self.body.span,
                 format!(
                     "broken MIR in {:?} ({}):\ninvalid source scope {:?}",