4 files changed, 9 insertions, 11 deletions
diff --git a/compiler/rustc_mir_transform/src/cost_checker.rs b/compiler/rustc_mir_transform/src/cost_checker.rs
index 79bed960b95..2c692c95003 100644
--- a/compiler/rustc_mir_transform/src/cost_checker.rs
+++ b/compiler/rustc_mir_transform/src/cost_checker.rs
@@ -70,7 +70,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
             TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
                 let fn_ty = self.instantiate_ty(f.const_.ty());
                 self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind()
-                    && tcx.is_intrinsic(def_id)
+                    && tcx.intrinsic(def_id).is_some()
                 {
                     // Don't give intrinsics the extra penalty for calls
                     INSTR_COST
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index d936c64c55c..73102a5f026 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -289,9 +289,9 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         if args.is_empty() {
             return;
         }
-        let ty = args.type_at(0);
 
-        let known_is_valid = intrinsic_assert_panics(self.tcx, self.param_env, ty, intrinsic_name);
+        let known_is_valid =
+            intrinsic_assert_panics(self.tcx, self.param_env, args[0], intrinsic_name);
         match known_is_valid {
             // We don't know the layout or it's not validity assertion at all, don't touch it
             None => {}
@@ -310,10 +310,11 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
 fn intrinsic_assert_panics<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
+    arg: ty::GenericArg<'tcx>,
     intrinsic_name: Symbol,
 ) -> Option<bool> {
     let requirement = ValidityRequirement::from_intrinsic(intrinsic_name)?;
+    let ty = arg.expect_ty();
     Some(!tcx.check_validity_requirement((requirement, param_env.and(ty))).ok()?)
 }
 
@@ -322,9 +323,8 @@ fn resolve_rust_intrinsic<'tcx>(
     func_ty: Ty<'tcx>,
 ) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
     if let ty::FnDef(def_id, args) = *func_ty.kind() {
-        if tcx.is_intrinsic(def_id) {
-            return Some((tcx.item_name(def_id), args));
-        }
+        let name = tcx.intrinsic(def_id)?;
+        return Some((name, args));
     }
     None
 }
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index fb174192b84..7f0e6f90dbb 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -161,8 +161,7 @@ fn remap_mir_for_const_eval_select<'tcx>(
                 fn_span,
                 ..
             } if let ty::FnDef(def_id, _) = *const_.ty().kind()
-                && tcx.item_name(def_id) == sym::const_eval_select
-                && tcx.is_intrinsic(def_id) =>
+                && matches!(tcx.intrinsic(def_id), Some(sym::const_eval_select)) =>
             {
                 let [tupled_args, called_in_const, called_at_rt]: [_; 3] =
                     std::mem::take(args).try_into().unwrap();
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index f43b85173d4..a0af902c4e1 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -14,9 +14,8 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
             if let TerminatorKind::Call { func, args, destination, target, .. } =
                 &mut terminator.kind
                 && let ty::FnDef(def_id, generic_args) = *func.ty(local_decls, tcx).kind()
-                && tcx.is_intrinsic(def_id)
+                && let Some(intrinsic_name) = tcx.intrinsic(def_id)
             {
-                let intrinsic_name = tcx.item_name(def_id);
                 match intrinsic_name {
                     sym::unreachable => {
                         terminator.kind = TerminatorKind::Unreachable;