diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 4a8894983b98d..6e9e0332faf60 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -576,12 +576,12 @@ pub enum PassKind {
     Module,
 }
 
-/// LLVMRustThinLTOData
+// LLVMRustThinLTOData
 extern "C" {
     pub type ThinLTOData;
 }
 
-/// LLVMRustThinLTOBuffer
+// LLVMRustThinLTOBuffer
 extern "C" {
     pub type ThinLTOBuffer;
 }
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 46b90baa5858a..72b8d8bb297a6 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1086,6 +1086,16 @@ impl EarlyLintPass for UnusedDocComment {
     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
     }
+
+    fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
+        warn_if_doc(cx, block.span, "block", &block.attrs());
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        if let ast::ItemKind::ForeignMod(_) = item.kind {
+            warn_if_doc(cx, item.span, "extern block", &item.attrs);
+        }
+    }
 }
 
 declare_lint! {
diff --git a/library/portable-simd/crates/core_simd/src/intrinsics.rs b/library/portable-simd/crates/core_simd/src/intrinsics.rs
index 4c68d11e8932a..cf2c0a02351ed 100644
--- a/library/portable-simd/crates/core_simd/src/intrinsics.rs
+++ b/library/portable-simd/crates/core_simd/src/intrinsics.rs
@@ -18,9 +18,10 @@
 //!
 //! Unless stated otherwise, all intrinsics for binary operations require SIMD vectors of equal types and lengths.
 
-/// These intrinsics aren't linked directly from LLVM and are mostly undocumented, however they are
-/// mostly lowered to the matching LLVM instructions by the compiler in a fairly straightforward manner.
-/// The associated LLVM instruction or intrinsic is documented alongside each Rust intrinsic function.
+
+// These intrinsics aren't linked directly from LLVM and are mostly undocumented, however they are
+// mostly lowered to the matching LLVM instructions by the compiler in a fairly straightforward manner.
+// The associated LLVM instruction or intrinsic is documented alongside each Rust intrinsic function.
 extern "platform-intrinsic" {
     /// add/fadd
     pub(crate) fn simd_add<T>(x: T, y: T) -> T;
diff --git a/library/stdarch b/library/stdarch
index b4a0e07552cf9..bcbe010614f39 160000
--- a/library/stdarch
+++ b/library/stdarch
@@ -1 +1 @@
-Subproject commit b4a0e07552cf90ef8f1a5b775bf70e4db94b3d63
+Subproject commit bcbe010614f398ec86f3a9274d22e33e5f2ee60b
diff --git a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
index 258f9e4831f9a..54d86c31fb4fb 100644
--- a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
@@ -29,4 +29,18 @@ fn doc_comment_on_expr(num: u8) -> bool {
 fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
 //~^ ERROR: unused doc comment
 
+fn doc_comment_on_block() {
+    /// unused doc comment
+    //~^ ERROR: unused doc comment
+    {
+        let x = 12;
+    }
+}
+
+/// unused doc comment
+//~^ ERROR: unused doc comment
+extern "C" {
+    fn foo();
+}
+
 fn main() {}
diff --git a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
index 3ce1df71a2ed5..30a96af583af7 100644
--- a/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
@@ -49,6 +49,32 @@ LL | fn doc_comment_on_generic<#[doc = "x"] T>(val: T) {}
    |
    = help: use `//` for a plain comment
 
+error: unused doc comment
+  --> $DIR/unused-doc-comments-edge-cases.rs:33:5
+   |
+LL |       /// unused doc comment
+   |       ^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL | /     {
+LL | |         let x = 12;
+LL | |     }
+   | |_____- rustdoc does not generate documentation for expressions
+   |
+   = help: use `//` for a plain comment
+
+error: unused doc comment
+  --> $DIR/unused-doc-comments-edge-cases.rs:40:1
+   |
+LL |   /// unused doc comment
+   |   ^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL | / extern "C" {
+LL | |     fn foo();
+LL | | }
+   | |_- rustdoc does not generate documentation for extern block
+   |
+   = help: use `//` for a plain comment
+
 error[E0308]: mismatched types
   --> $DIR/unused-doc-comments-edge-cases.rs:14:9
    |
@@ -63,7 +89,7 @@ help: you might have meant to return this value
 LL |         return true;
    |         ++++++     +
 
-error: aborting due to 6 previous errors
+error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0308, E0658.
 For more information about an error, try `rustc --explain E0308`.