Don't generate functions with the rustc_intrinsic_must_be_overridden attribute

Author: dianqk

compiler/rustc_monomorphize/src/collector.rs

@@ -957,6 +957,11 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -
         return false;
     }
 
+    if tcx.has_attr(instance.def_id(), sym::rustc_intrinsic_must_be_overridden) {
+        // Functions with the attribute `rustc_intrinsic_must_be_overridden` never be called.
+        return false;
+    }
+
     if !tcx.is_mir_available(def_id) {
         tcx.dcx().emit_fatal(NoOptimizedMir {
             span: tcx.def_span(def_id),

tests/codegen/intrinsics/rustc_intrinsic_must_be_overridden.rs

@@ -0,0 +1,14 @@
+//@ revisions: OPT0 OPT1
+//@ [OPT0] compile-flags: -Copt-level=0
+//@ [OPT1] compile-flags: -Copt-level=1
+//@ compile-flags: -Cno-prepopulate-passes
+
+#![crate_type = "lib"]
+#![feature(core_intrinsics)]
+
+// CHECK-NOT: core::intrinsics::size_of_val
+
+#[no_mangle]
+pub unsafe fn size_of_val(ptr: *const i32) -> usize {
+    core::intrinsics::size_of_val(ptr)
+}