remove retag_box_to_raw, it is no longer needed

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -658,10 +658,6 @@ pub fn check_intrinsic_type(
             sym::simd_shuffle => (3, 0, vec![param(0), param(0), param(1)], param(2)),
             sym::simd_shuffle_generic => (2, 1, vec![param(0), param(0)], param(1)),
 
-            sym::retag_box_to_raw => {
-                (2, 0, vec![Ty::new_mut_ptr(tcx, param(0))], Ty::new_mut_ptr(tcx, param(0)))
-            }
-
             other => {
                 tcx.dcx().emit_err(UnrecognizedIntrinsicFunction { span, name: other });
                 return;

compiler/rustc_span/src/symbol.rs

@@ -1463,7 +1463,6 @@ symbols! {
         residual,
         result,
         resume,
-        retag_box_to_raw,
         return_position_impl_trait_in_trait,
         return_type_notation,
         rhs,

library/core/src/intrinsics.rs

@@ -2709,19 +2709,6 @@ pub unsafe fn vtable_size(_ptr: *const ()) -> usize {
     unreachable!()
 }
 
-/// Retag a box pointer as part of casting it to a raw pointer. This is the `Box` equivalent of
-/// `(x: &mut T) as *mut T`. The input pointer must be the pointer of a `Box` (passed as raw pointer
-/// to avoid all questions around move semantics and custom allocators), and `A` must be the `Box`'s
-/// allocator.
-#[unstable(feature = "core_intrinsics", issue = "none")]
-#[rustc_nounwind]
-#[cfg_attr(not(bootstrap), rustc_intrinsic)]
-#[cfg_attr(bootstrap, inline)]
-pub unsafe fn retag_box_to_raw<T: ?Sized, A>(ptr: *mut T) -> *mut T {
-    // Miri needs to adjust the provenance, but for regular codegen this is not needed
-    ptr
-}
-
 // Some functions are defined here because they accidentally got made
 // available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
 // (`transmute` also falls into this category, but it cannot be wrapped due to the

src/tools/miri/src/borrow_tracker/mod.rs

@@ -5,7 +5,7 @@ use std::num::NonZero;
 use smallvec::SmallVec;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_middle::{mir::RetagKind, ty::Ty};
+use rustc_middle::mir::RetagKind;
 use rustc_target::abi::Size;
 
 use crate::*;
@@ -291,19 +291,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         }
     }
 
-    fn retag_box_to_raw(
-        &mut self,
-        val: &ImmTy<'tcx, Provenance>,
-        alloc_ty: Ty<'tcx>,
-    ) -> InterpResult<'tcx, ImmTy<'tcx, Provenance>> {
-        let this = self.eval_context_mut();
-        let method = this.machine.borrow_tracker.as_ref().unwrap().borrow().borrow_tracker_method;
-        match method {
-            BorrowTrackerMethod::StackedBorrows => this.sb_retag_box_to_raw(val, alloc_ty),
-            BorrowTrackerMethod::TreeBorrows => this.tb_retag_box_to_raw(val, alloc_ty),
-        }
-    }
-
     fn retag_place_contents(
         &mut self,
         kind: RetagKind,

src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs

@@ -865,24 +865,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         this.sb_retag_reference(val, new_perm, RetagInfo { cause, in_field: false })
     }
 
-    fn sb_retag_box_to_raw(
-        &mut self,
-        val: &ImmTy<'tcx, Provenance>,
-        alloc_ty: Ty<'tcx>,
-    ) -> InterpResult<'tcx, ImmTy<'tcx, Provenance>> {
-        let this = self.eval_context_mut();
-        let is_global_alloc = alloc_ty.ty_adt_def().is_some_and(|adt| {
-            let global_alloc = this.tcx.require_lang_item(rustc_hir::LangItem::GlobalAlloc, None);
-            adt.did() == global_alloc
-        });
-        if is_global_alloc {
-            // Retag this as-if it was a mutable reference.
-            this.sb_retag_ptr_value(RetagKind::Raw, val)
-        } else {
-            Ok(val.clone())
-        }
-    }
-
     fn sb_retag_place_contents(
         &mut self,
         kind: RetagKind,

src/tools/miri/src/borrow_tracker/tree_borrows/mod.rs

@@ -392,15 +392,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         }
     }
 
-    fn tb_retag_box_to_raw(
-        &mut self,
-        val: &ImmTy<'tcx, Provenance>,
-        _alloc_ty: Ty<'tcx>,
-    ) -> InterpResult<'tcx, ImmTy<'tcx, Provenance>> {
-        // Casts to raw pointers are NOPs in Tree Borrows.
-        Ok(val.clone())
-    }
-
     /// Retag all pointers that are stored in this place.
     fn tb_retag_place_contents(
         &mut self,

src/tools/miri/src/shims/intrinsics/mod.rs

@@ -140,18 +140,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
                 this.write_pointer(Pointer::new(ptr.provenance, masked_addr), dest)?;
             }
-            "retag_box_to_raw" => {
-                let [ptr] = check_arg_count(args)?;
-                let alloc_ty = generic_args[1].expect_ty();
-
-                let val = this.read_immediate(ptr)?;
-                let new_val = if this.machine.borrow_tracker.is_some() {
-                    this.retag_box_to_raw(&val, alloc_ty)?
-                } else {
-                    val
-                };
-                this.write_immediate(*new_val, dest)?;
-            }
 
             // We want to return either `true` or `false` at random, or else something like
             // ```