Auto merge of #3724 - bjorn3:use_symbol_name_query, r=RalfJung

Use the symbol_name query instead of trying to infer from the link_name attribute

This prevents the calculated name from going out of sync with exported_symbols. It also avoids having to special case the panic_impl lang item.

It also makes it easier to fix miri with rust-lang/rust#127173.

src/helpers.rs

@@ -24,7 +24,7 @@ use rustc_middle::ty::{
     FloatTy, IntTy, Ty, TyCtxt, UintTy,
 };
 use rustc_session::config::CrateType;
-use rustc_span::{sym, Span, Symbol};
+use rustc_span::{Span, Symbol};
 use rustc_target::abi::{Align, FieldIdx, FieldsShape, Size, Variants};
 use rustc_target::spec::abi::Abi;
 
@@ -1182,14 +1182,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         this.alloc_mark_immutable(provenance.get_alloc_id().unwrap()).unwrap();
     }
 
-    fn item_link_name(&self, def_id: DefId) -> Symbol {
-        let tcx = self.eval_context_ref().tcx;
-        match tcx.get_attrs(def_id, sym::link_name).filter_map(|a| a.value_str()).next() {
-            Some(name) => name,
-            None => tcx.item_name(def_id),
-        }
-    }
-
     /// Converts `src` from floating point to integer type `dest_ty`
     /// after rounding with mode `round`.
     /// Returns `None` if `f` is NaN or out of range.

src/machine.rs

@@ -954,7 +954,7 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
             // foreign function
             // Any needed call to `goto_block` will be performed by `emulate_foreign_item`.
             let args = ecx.copy_fn_args(args); // FIXME: Should `InPlace` arguments be reset to uninit?
-            let link_name = ecx.item_link_name(instance.def_id());
+            let link_name = Symbol::intern(ecx.tcx.symbol_name(instance).name);
             return ecx.emulate_foreign_item(link_name, abi, &args, dest, ret, unwind);
         }
 
@@ -1050,7 +1050,7 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
         ecx: &MiriInterpCx<'tcx>,
         def_id: DefId,
     ) -> InterpResult<'tcx, StrictPointer> {
-        let link_name = ecx.item_link_name(def_id);
+        let link_name = Symbol::intern(ecx.tcx.symbol_name(Instance::mono(*ecx.tcx, def_id)).name);
         if let Some(&ptr) = ecx.machine.extern_statics.get(&link_name) {
             // Various parts of the engine rely on `get_alloc_info` for size and alignment
             // information. That uses the type information of this static.

src/shims/foreign_items.rs

@@ -46,24 +46,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         unwind: mir::UnwindAction,
     ) -> InterpResult<'tcx, Option<(&'tcx mir::Body<'tcx>, ty::Instance<'tcx>)>> {
         let this = self.eval_context_mut();
-        let tcx = this.tcx.tcx;
 
         // Some shims forward to other MIR bodies.
         match link_name.as_str() {
-            // This matches calls to the foreign item `panic_impl`.
-            // The implementation is provided by the function with the `#[panic_handler]` attribute.
-            "panic_impl" => {
-                // We don't use `check_shim` here because we are just forwarding to the lang
-                // item. Argument count checking will be performed when the returned `Body` is
-                // called.
-                this.check_abi_and_shim_symbol_clash(abi, Abi::Rust, link_name)?;
-                let panic_impl_id = tcx.lang_items().panic_impl().unwrap();
-                let panic_impl_instance = ty::Instance::mono(tcx, panic_impl_id);
-                return Ok(Some((
-                    this.load_mir(panic_impl_instance.def, None)?,
-                    panic_impl_instance,
-                )));
-            }
             "__rust_alloc_error_handler" => {
                 // Forward to the right symbol that implements this function.
                 let Some(handler_kind) = this.tcx.alloc_error_handler_kind(()) else {