diff --git a/src/helpers.rs b/src/helpers.rs
index d1429a0be1..29ed94a2e4 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -17,6 +17,7 @@ use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, MaybeResult, TyAndLayout};
 use rustc_middle::ty::{self, Binder, FloatTy, FnSig, IntTy, Ty, TyCtxt, UintTy};
 use rustc_session::config::CrateType;
 use rustc_span::{Span, Symbol};
+use rustc_symbol_mangling::mangle_internal_symbol;
 use rustc_target::callconv::{Conv, FnAbi};
 
 use crate::*;
@@ -1258,6 +1259,18 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         interp_ok(array)
     }
+
+    fn mangle_internal_symbol<'a>(&'a mut self, name: &'static str) -> &'a str
+    where
+        'tcx: 'a,
+    {
+        let this = self.eval_context_mut();
+        let tcx = *this.tcx;
+        this.machine
+            .mangle_internal_symbol_cache
+            .entry(name)
+            .or_insert_with(|| mangle_internal_symbol(tcx, name))
+    }
 }
 
 impl<'tcx> MiriMachine<'tcx> {
diff --git a/src/machine.rs b/src/machine.rs
index bd901a4ed1..fb99bdc517 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -611,6 +611,9 @@ pub struct MiriMachine<'tcx> {
     pub(crate) reject_in_isolation_warned: RefCell<FxHashSet<String>>,
     /// Remembers which int2ptr casts we have already warned about.
     pub(crate) int2ptr_warned: RefCell<FxHashSet<Span>>,
+
+    /// Cache for `mangle_internal_symbol`.
+    pub(crate) mangle_internal_symbol_cache: FxHashMap<&'static str, String>,
 }
 
 impl<'tcx> MiriMachine<'tcx> {
@@ -757,6 +760,7 @@ impl<'tcx> MiriMachine<'tcx> {
             native_call_mem_warned: Cell::new(false),
             reject_in_isolation_warned: Default::default(),
             int2ptr_warned: Default::default(),
+            mangle_internal_symbol_cache: Default::default(),
         }
     }
 
@@ -930,6 +934,7 @@ impl VisitProvenance for MiriMachine<'_> {
             native_call_mem_warned: _,
             reject_in_isolation_warned: _,
             int2ptr_warned: _,
+            mangle_internal_symbol_cache: _,
         } = self;
 
         threads.visit_provenance(visit);
diff --git a/src/shims/foreign_items.rs b/src/shims/foreign_items.rs
index 03c6081e99..52c16a0c2e 100644
--- a/src/shims/foreign_items.rs
+++ b/src/shims/foreign_items.rs
@@ -9,10 +9,9 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::CrateNum;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::AllocInit;
-use rustc_middle::ty::Ty;
+use rustc_middle::ty::{Instance, Ty};
 use rustc_middle::{mir, ty};
 use rustc_span::Symbol;
-use rustc_symbol_mangling::mangle_internal_symbol;
 use rustc_target::callconv::{Conv, FnAbi};
 
 use self::helpers::{ToHost, ToSoft};
@@ -52,7 +51,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         // Some shims forward to other MIR bodies.
         match link_name.as_str() {
-            name if name == mangle_internal_symbol(*this.tcx, "__rust_alloc_error_handler") => {
+            name if name == this.mangle_internal_symbol("__rust_alloc_error_handler") => {
                 // Forward to the right symbol that implements this function.
                 let Some(handler_kind) = this.tcx.alloc_error_handler_kind(()) else {
                     // in real code, this symbol does not exist without an allocator
@@ -60,11 +59,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         "`__rust_alloc_error_handler` cannot be called when no alloc error handler is set"
                     );
                 };
-                let name =
-                    mangle_internal_symbol(*this.tcx, alloc_error_handler_name(handler_kind));
-                let handler = this
-                    .lookup_exported_symbol(Symbol::intern(&name))?
-                    .expect("missing alloc error handler symbol");
+                let name = Symbol::intern(
+                    this.mangle_internal_symbol(alloc_error_handler_name(handler_kind)),
+                );
+                let handler =
+                    this.lookup_exported_symbol(name)?.expect("missing alloc error handler symbol");
                 return interp_ok(Some(handler));
             }
             _ => {}
@@ -138,30 +137,22 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // Find it if it was not cached.
                 let mut instance_and_crate: Option<(ty::Instance<'_>, CrateNum)> = None;
                 helpers::iter_exported_symbols(tcx, |cnum, def_id| {
+                    let attrs = tcx.codegen_fn_attrs(def_id);
+                    // Skip over imports of items.
                     if tcx.is_foreign_item(def_id) {
-                        // Skip over imports of items
                         return interp_ok(());
                     }
-
-                    let attrs = tcx.codegen_fn_attrs(def_id);
-                    // FIXME use tcx.symbol_name(instance) instead
-                    let symbol_name = if let Some(export_name) = attrs.export_name {
-                        export_name
-                    } else if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
-                        || attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
+                    // Skip over items without an explicitly defined symbol name.
+                    if !(attrs.export_name.is_some()
+                        || attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
+                        || attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL))
                     {
-                        tcx.item_name(def_id)
-                    } else {
-                        // Skip over items without an explicitly defined symbol name.
                         return interp_ok(());
-                    };
-                    let symbol_name =
-                        if attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
-                            Symbol::intern(&mangle_internal_symbol(tcx, symbol_name.as_str()))
-                        } else {
-                            symbol_name
-                        };
-                    if symbol_name == link_name {
+                    }
+
+                    let instance = Instance::mono(tcx, def_id);
+                    let symbol_name = tcx.symbol_name(instance).name;
+                    if symbol_name == link_name.as_str() {
                         if let Some((original_instance, original_cnum)) = instance_and_crate {
                             // Make sure we are consistent wrt what is 'first' and 'second'.
                             let original_span = tcx.def_span(original_instance.def_id()).data();
@@ -505,9 +496,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
 
             // Rust allocation
-            name if name == mangle_internal_symbol(*this.tcx, "__rust_alloc")
-                || name == "miri_alloc" =>
-            {
+            name if name == this.mangle_internal_symbol("__rust_alloc") || name == "miri_alloc" => {
                 let default = |ecx: &mut MiriInterpCx<'tcx>| {
                     // Only call `check_shim` when `#[global_allocator]` isn't used. When that
                     // macro is used, we act like no shim exists, so that the exported function can run.
@@ -540,7 +529,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     _ => return this.emulate_allocator(default),
                 }
             }
-            name if name == mangle_internal_symbol(*this.tcx, "__rust_alloc_zeroed") => {
+            name if name == this.mangle_internal_symbol("__rust_alloc_zeroed") => {
                 return this.emulate_allocator(|this| {
                     // See the comment for `__rust_alloc` why `check_shim` is only called in the
                     // default case.
@@ -559,7 +548,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     this.write_pointer(ptr, dest)
                 });
             }
-            name if name == mangle_internal_symbol(*this.tcx, "__rust_dealloc")
+            name if name == this.mangle_internal_symbol("__rust_dealloc")
                 || name == "miri_dealloc" =>
             {
                 let default = |ecx: &mut MiriInterpCx<'tcx>| {
@@ -592,7 +581,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     _ => return this.emulate_allocator(default),
                 }
             }
-            name if name == mangle_internal_symbol(*this.tcx, "__rust_realloc") => {
+            name if name == this.mangle_internal_symbol("__rust_realloc") => {
                 return this.emulate_allocator(|this| {
                     // See the comment for `__rust_alloc` why `check_shim` is only called in the
                     // default case.