From 91f491ecf27f39c1ebba48c7e011a212dde7013c Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Tue, 15 Jun 2021 14:52:16 +0200
Subject: [PATCH 1/2] Don't mark "safe" intrinsics as unsafe

---
 src/librustdoc/clean/mod.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index d1c18821ea644..2281a9f69ee34 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -26,6 +26,8 @@ use rustc_mir::const_eval::{is_const_fn, is_unstable_const_fn};
 use rustc_span::hygiene::{AstPass, MacroKind};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{self, ExpnKind};
+use rustc_target::spec::abi::Abi;
+use rustc_typeck::check::intrinsic::intrinsic_operation_unsafety;
 use rustc_typeck::hir_ty_to_ty;
 
 use std::collections::hash_map::Entry;
@@ -2132,7 +2134,11 @@ impl Clean<Item> for (&hir::ForeignItem<'_>, Option<Symbol>) {
                         decl,
                         generics,
                         header: hir::FnHeader {
-                            unsafety: hir::Unsafety::Unsafe,
+                            unsafety: if abi == Abi::RustIntrinsic {
+                                intrinsic_operation_unsafety(item.ident.name)
+                            } else {
+                                hir::Unsafety::Unsafe
+                            },
                             abi,
                             constness: hir::Constness::NotConst,
                             asyncness: hir::IsAsync::NotAsync,

From f6830403b3ba09ab8e3b07845061b5fbd30e249d Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Tue, 15 Jun 2021 16:08:18 +0200
Subject: [PATCH 2/2] Add test for safe intrinsics

---
 src/test/rustdoc/safe-intrinsic.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 src/test/rustdoc/safe-intrinsic.rs

diff --git a/src/test/rustdoc/safe-intrinsic.rs b/src/test/rustdoc/safe-intrinsic.rs
new file mode 100644
index 0000000000000..d3bb8514b7e43
--- /dev/null
+++ b/src/test/rustdoc/safe-intrinsic.rs
@@ -0,0 +1,20 @@
+#![feature(intrinsics)]
+#![feature(no_core)]
+
+#![no_core]
+#![crate_name = "foo"]
+
+extern "rust-intrinsic" {
+    // @has 'foo/fn.abort.html'
+    // @has - '//pre[@class="rust fn"]' 'pub extern "rust-intrinsic" fn abort() -> !'
+    pub fn abort() -> !;
+    // @has 'foo/fn.unreachable.html'
+    // @has - '//pre[@class="rust fn"]' 'pub unsafe extern "rust-intrinsic" fn unreachable() -> !'
+    pub fn unreachable() -> !;
+}
+
+extern "C" {
+    // @has 'foo/fn.needs_drop.html'
+    // @has - '//pre[@class="rust fn"]' 'pub unsafe extern "C" fn needs_drop() -> !'
+    pub fn needs_drop() -> !;
+}