Auto merge of #122869 - matthiaskrgr:rollup-0navj4l, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #121619 (Experimental feature postfix match)
 - #122370 (Gracefully handle `AnonConst` in `diagnostic_hir_wf_check()`)
 - #122537 (interpret/allocation: fix aliasing issue in interpreter and refactor getters a bit)
 - #122542 (coverage: Clean up marker statements that aren't needed later)
 - #122800 (Add `NonNull::<[T]>::is_empty`.)
 - #122820 (Stop using `<DefId as Ord>` in various diagnostic situations)
 - #122847 (Suggest `RUST_MIN_STACK` workaround on overflow)
 - #122855 (Fix Itanium mangling usizes)
 - #122863 (add more ice tests )

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

5 files changed, 45 insertions, 17 deletions

diff --git a/compiler/rustc_middle/src/mir/consts.rs b/compiler/rustc_middle/src/mir/consts.rs
index 214297b9869..02185cbeacf 100644
--- a/compiler/rustc_middle/src/mir/consts.rs
+++ b/compiler/rustc_middle/src/mir/consts.rs
@@ -456,7 +456,7 @@ impl<'tcx> Const<'tcx> {
 }
 
 /// An unevaluated (potentially generic) constant used in MIR.
-#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable)]
 #[derive(Hash, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct UnevaluatedConst<'tcx> {
     pub def: DefId,
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index 645a417c322..588aa1f40d7 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/compiler/rustc_middle/src/mir/coverage.rs
@@ -88,14 +88,13 @@ pub enum CoverageKind {
     /// Marks a span that might otherwise not be represented in MIR, so that
     /// coverage instrumentation can associate it with its enclosing block/BCB.
     ///
-    /// Only used by the `InstrumentCoverage` pass, and has no effect during
-    /// codegen.
+    /// Should be erased before codegen (at some point after `InstrumentCoverage`).
     SpanMarker,
 
     /// Marks its enclosing basic block with an ID that can be referred to by
     /// side data in [`BranchInfo`].
     ///
-    /// Has no effect during codegen.
+    /// Should be erased before codegen (at some point after `InstrumentCoverage`).
     BlockMarker { id: BlockMarkerId },
 
     /// Marks the point in MIR control flow represented by a coverage counter.
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 4047891d769..00faa211853 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -37,9 +37,16 @@ pub trait AllocBytes:
     /// Create a zeroed `AllocBytes` of the specified size and alignment.
     /// Returns `None` if we ran out of memory on the host.
     fn zeroed(size: Size, _align: Align) -> Option<Self>;
+
+    /// Gives direct access to the raw underlying storage.
+    ///
+    /// Crucially this pointer is compatible with:
+    /// - other pointers retunred by this method, and
+    /// - references returned from `deref()`, as long as there was no write.
+    fn as_mut_ptr(&mut self) -> *mut u8;
 }
 
-// Default `bytes` for `Allocation` is a `Box<[u8]>`.
+/// Default `bytes` for `Allocation` is a `Box<u8>`.
 impl AllocBytes for Box<[u8]> {
     fn from_bytes<'a>(slice: impl Into<Cow<'a, [u8]>>, _align: Align) -> Self {
         Box::<[u8]>::from(slice.into())
@@ -51,6 +58,11 @@ impl AllocBytes for Box<[u8]> {
         let bytes = unsafe { bytes.assume_init() };
         Some(bytes)
     }
+
+    fn as_mut_ptr(&mut self) -> *mut u8 {
+        // Carefully avoiding any intermediate references.
+        ptr::addr_of_mut!(**self).cast()
+    }
 }
 
 /// This type represents an Allocation in the Miri/CTFE core engine.
@@ -399,10 +411,6 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
 
 /// Byte accessors.
 impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes> {
-    pub fn base_addr(&self) -> *const u8 {
-        self.bytes.as_ptr()
-    }
-
     /// This is the entirely abstraction-violating way to just grab the raw bytes without
     /// caring about provenance or initialization.
     ///
@@ -452,13 +460,14 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         Ok(self.get_bytes_unchecked(range))
     }
 
-    /// Just calling this already marks everything as defined and removes provenance,
-    /// so be sure to actually put data there!
+    /// This is the entirely abstraction-violating way to just get mutable access to the raw bytes.
+    /// Just calling this already marks everything as defined and removes provenance, so be sure to
+    /// actually overwrite all the data there!
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     /// Most likely, you want to use the `PlaceTy` and `OperandTy`-based methods
     /// on `InterpCx` instead.
-    pub fn get_bytes_mut(
+    pub fn get_bytes_unchecked_for_overwrite(
         &mut self,
         cx: &impl HasDataLayout,
         range: AllocRange,
@@ -469,8 +478,9 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         Ok(&mut self.bytes[range.start.bytes_usize()..range.end().bytes_usize()])
     }
 
-    /// A raw pointer variant of `get_bytes_mut` that avoids invalidating existing aliases into this memory.
-    pub fn get_bytes_mut_ptr(
+    /// A raw pointer variant of `get_bytes_unchecked_for_overwrite` that avoids invalidating existing immutable aliases
+    /// into this memory.
+    pub fn get_bytes_unchecked_for_overwrite_ptr(
         &mut self,
         cx: &impl HasDataLayout,
         range: AllocRange,
@@ -479,10 +489,19 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         self.provenance.clear(range, cx)?;
 
         assert!(range.end().bytes_usize() <= self.bytes.len()); // need to do our own bounds-check
+        // Cruciall, we go via `AllocBytes::as_mut_ptr`, not `AllocBytes::deref_mut`.
         let begin_ptr = self.bytes.as_mut_ptr().wrapping_add(range.start.bytes_usize());
         let len = range.end().bytes_usize() - range.start.bytes_usize();
         Ok(ptr::slice_from_raw_parts_mut(begin_ptr, len))
     }
+
+    /// This gives direct mutable access to the entire buffer, just exposing their internal state
+    /// without reseting anything. Directly exposes `AllocBytes::as_mut_ptr`. Only works if
+    /// `OFFSET_IS_ADDR` is true.
+    pub fn get_bytes_unchecked_raw_mut(&mut self) -> *mut u8 {
+        assert!(Prov::OFFSET_IS_ADDR);
+        self.bytes.as_mut_ptr()
+    }
 }
 
 /// Reading and writing.
@@ -589,7 +608,8 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         };
 
         let endian = cx.data_layout().endian;
-        let dst = self.get_bytes_mut(cx, range)?;
+        // Yes we do overwrite all the bytes in `dst`.
+        let dst = self.get_bytes_unchecked_for_overwrite(cx, range)?;
         write_target_uint(endian, dst, bytes).unwrap();
 
         // See if we have to also store some provenance.
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 8bd872c1b19..731e050ca9b 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -284,8 +284,15 @@ rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);
 /// order of the category, thereby influencing diagnostic output.
 ///
 /// See also `rustc_const_eval::borrow_check::constraints`.
-#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 #[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
+#[derive(derivative::Derivative)]
+#[derivative(
+    PartialOrd,
+    Ord,
+    PartialOrd = "feature_allow_slow_enum",
+    Ord = "feature_allow_slow_enum"
+)]
 pub enum ConstraintCategory<'tcx> {
     Return(ReturnConstraint),
     Yield,
@@ -295,6 +302,7 @@ pub enum ConstraintCategory<'tcx> {
     Cast {
         /// Whether this is an unsizing cast and if yes, this contains the target type.
         /// Region variables are erased to ReErased.
+        #[derivative(PartialOrd = "ignore", Ord = "ignore")]
         unsize_to: Option<Ty<'tcx>>,
     },
 
@@ -304,7 +312,7 @@ pub enum ConstraintCategory<'tcx> {
     ClosureBounds,
 
     /// Contains the function type if available.
-    CallArgument(Option<Ty<'tcx>>),
+    CallArgument(#[derivative(PartialOrd = "ignore", Ord = "ignore")] Option<Ty<'tcx>>),
     CopyBound,
     SizedBound,
     Assignment,
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 0ab797134c0..752f5845afb 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -124,6 +124,7 @@ pub enum AnalysisPhase {
     /// * [`TerminatorKind::FalseEdge`]
     /// * [`StatementKind::FakeRead`]
     /// * [`StatementKind::AscribeUserType`]
+    /// * [`StatementKind::Coverage`] with [`CoverageKind::BlockMarker`] or [`CoverageKind::SpanMarker`]
     /// * [`Rvalue::Ref`] with `BorrowKind::Fake`
     ///
     /// Furthermore, `Deref` projections must be the first projection within any place (if they