diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 3547b45dfa71f..55e91f0952438 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -218,6 +218,8 @@ pub struct RenderOptions {
     pub extern_html_root_urls: BTreeMap<String, String>,
     /// If present, suffix added to CSS/JavaScript files when referencing them in generated pages.
     pub resource_suffix: String,
+    /// Links displayed on the crate root page.
+    pub crate_root_links: BTreeMap<String, String>,
     /// Whether to run the static CSS/JavaScript through a minifier when outputting them. `true` by
     /// default.
     //
@@ -270,6 +272,36 @@ impl Options {
     /// Parses the given command-line for options. If an error message or other early-return has
     /// been printed, returns `Err` with the exit code.
     pub fn from_matches(matches: &getopts::Matches) -> Result<Options, i32> {
+        fn parse_keyval_opt_internal(
+            matches: &getopts::Matches,
+            opt_name: &'static str,
+            empty_err: &'static str,
+            invalid_form_err: &'static str,
+        ) -> Result<BTreeMap<String, String>, &'static str> {
+            let mut externs = BTreeMap::new();
+            for arg in &(matches).opt_strs(opt_name) {
+                let mut parts = arg.splitn(2, '=');
+                let name = parts.next().ok_or(empty_err)?;
+                let url = parts.next().ok_or(invalid_form_err)?;
+                externs.insert(name.to_string(), url.to_string());
+            }
+
+            Ok(externs)
+        }
+        /// Extracts key-value arguments (such as for `--extern-html-root-url`)  from `matches` and returns
+        /// a map of crate names to the given URLs. If an argument was ill-formed, returns an error
+        /// describing the issue.
+        macro_rules! parse_keyval_opt {
+            ($matches:expr, $opt_name:literal) => {
+                parse_keyval_opt_internal(
+                    $matches,
+                    $opt_name,
+                    concat!("--", $opt_name, "must not be empty"),
+                    concat!("--", $opt_name, "must be of the form name=url"),
+                )
+            };
+        }
+
         // Check for unstable options.
         nightly_options::check_nightly_options(&matches, &opts());
 
@@ -366,7 +398,15 @@ impl Options {
             .map(|s| SearchPath::from_cli_opt(s, error_format))
             .collect();
         let externs = parse_externs(&matches, &debugging_options, error_format);
-        let extern_html_root_urls = match parse_extern_html_roots(&matches) {
+        let extern_html_root_urls = match parse_keyval_opt!(&matches, "extern-html-root-url") {
+            Ok(ex) => ex,
+            Err(err) => {
+                diag.struct_err(err).emit();
+                return Err(1);
+            }
+        };
+
+        let crate_root_links = match parse_keyval_opt!(&matches, "crate-root-link") {
             Ok(ex) => ex,
             Err(err) => {
                 diag.struct_err(err).emit();
@@ -609,6 +649,7 @@ impl Options {
                 generate_search_filter,
                 document_private,
                 document_hidden,
+                crate_root_links,
             },
             output_format,
         })
@@ -654,20 +695,3 @@ fn check_deprecated_options(matches: &getopts::Matches, diag: &rustc_errors::Han
         }
     }
 }
-
-/// Extracts `--extern-html-root-url` arguments from `matches` and returns a map of crate names to
-/// the given URLs. If an `--extern-html-root-url` argument was ill-formed, returns an error
-/// describing the issue.
-fn parse_extern_html_roots(
-    matches: &getopts::Matches,
-) -> Result<BTreeMap<String, String>, &'static str> {
-    let mut externs = BTreeMap::new();
-    for arg in &matches.opt_strs("extern-html-root-url") {
-        let mut parts = arg.splitn(2, '=');
-        let name = parts.next().ok_or("--extern-html-root-url must not be empty")?;
-        let url = parts.next().ok_or("--extern-html-root-url must be of the form name=url")?;
-        externs.insert(name.to_string(), url.to_string());
-    }
-
-    Ok(externs)
-}
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 5fb2d9f6f917c..3c403a3f17d0d 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -157,6 +157,8 @@ crate struct SharedContext {
     pub edition: Edition,
     pub codes: ErrorCodes,
     playground: Option<markdown::Playground>,
+    /// Links displayed on the crate root page.
+    pub crate_root_links: BTreeMap<String, String>,
 }
 
 impl Context {
@@ -396,6 +398,7 @@ impl FormatRenderer for Context {
             resource_suffix,
             static_root_path,
             generate_search_filter,
+            crate_root_links,
             ..
         } = options;
 
@@ -466,6 +469,7 @@ impl FormatRenderer for Context {
             edition,
             codes: ErrorCodes::from(UnstableFeatures::from_environment().is_nightly_build()),
             playground,
+            crate_root_links,
         };
 
         // Add the default themes to the `Vec` of stylepaths
@@ -3895,6 +3899,27 @@ fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer, cache: &Ca
     }
 
     write!(buffer, "<div class=\"sidebar-elems\">");
+
+    if it.is_crate() && !cx.shared.crate_root_links.is_empty() {
+        let mut links_html = String::new();
+        for (name, url) in &cx.shared.crate_root_links {
+            links_html.push_str(&format!(
+                "<li><a href='{}'>{}</a></li>",
+                Escape(url),
+                Escape(name),
+            ));
+        }
+        write!(
+            buffer,
+            "<div class='block items'>\
+            <ul>\
+            {}\
+            </ul>\
+            </div>",
+            links_html
+        );
+    };
+
     if it.is_crate() {
         write!(
             buffer,
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 65bc089faf428..b7bcc65fd9751 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -406,6 +406,9 @@ fn opts() -> Vec<RustcOptGroup> {
                 "specified the rustc-like binary to use as the test builder",
             )
         }),
+        unstable("crate-root-link", |o| {
+            o.optmulti("", "crate-root-link", "", "Specifies links to display on the crate root")
+        }),
     ]
 }
 
diff --git a/src/stdarch b/src/stdarch
new file mode 160000
index 0000000000000..45340c0e2fdad
--- /dev/null
+++ b/src/stdarch
@@ -0,0 +1 @@
+Subproject commit 45340c0e2fdadf2f131ef43cb683b5cafab0ff15
diff --git a/x.py b/x.py
index 7973730ef177c..6186ebb5d48a5 100755
--- a/x.py
+++ b/x.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # This file is only a "symlink" to bootstrap.py, all logic should go there.