Auto merge of #142358 - matthiaskrgr:rollup-fxe6m7k, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#141967 (Configure bootstrap backport nominations through triagebot)
 - rust-lang/rust#142042 (Make E0621 missing lifetime suggestion verbose)
 - rust-lang/rust#142272 (tests: Change ABIs in tests to more future-resilient ones)
 - rust-lang/rust#142282 (Only run `citool` tests on the `auto` branch)
 - rust-lang/rust#142297 (Implement `//@ needs-target-std` compiletest directive)
 - rust-lang/rust#142298 (Make loongarch-none target maintainers more easily pingable)
 - rust-lang/rust#142306 (Dont unwrap and re-wrap typing envs)
 - rust-lang/rust#142324 (Remove unneeded `FunctionCx` from some codegen methods)
 - rust-lang/rust#142328 (feat: Add `bit_width` for unsigned integer types)

Failed merges:

 - rust-lang/rust#141639 (Expose discriminant values in stable_mir)

r? `@ghost`
`@rustbot` modify labels: rollup

8 files changed, 33 insertions, 3 deletions

diff --git a/src/bootstrap/src/core/config/toml/target.rs b/src/bootstrap/src/core/config/toml/target.rs
index 7f074d1b25e..b8fc3e74c35 100644
--- a/src/bootstrap/src/core/config/toml/target.rs
+++ b/src/bootstrap/src/core/config/toml/target.rs
@@ -84,7 +84,7 @@ pub struct Target {
 impl Target {
     pub fn from_triple(triple: &str) -> Self {
         let mut target: Self = Default::default();
-        if triple.contains("-none") || triple.contains("nvptx") || triple.contains("switch") {
+        if !build_helper::targets::target_supports_std(triple) {
             target.no_std = true;
         }
         if triple.contains("emscripten") {
diff --git a/src/build_helper/src/lib.rs b/src/build_helper/src/lib.rs
index 1f5cf723641..05de8fd2d42 100644
--- a/src/build_helper/src/lib.rs
+++ b/src/build_helper/src/lib.rs
@@ -6,6 +6,7 @@ pub mod fs;
 pub mod git;
 pub mod metrics;
 pub mod stage0_parser;
+pub mod targets;
 pub mod util;
 
 /// The default set of crates for opt-dist to collect LLVM profiles.
diff --git a/src/build_helper/src/targets.rs b/src/build_helper/src/targets.rs
new file mode 100644
index 00000000000..cccc413368b
--- /dev/null
+++ b/src/build_helper/src/targets.rs
@@ -0,0 +1,11 @@
+// FIXME(#142296): this hack is because there is no reliable way (yet) to determine whether a given
+// target supports std. In the long-term, we should try to implement a way to *reliably* determine
+// target (std) metadata.
+//
+// NOTE: this is pulled out to `build_helpers` to share this hack between `bootstrap` and
+// `compiletest`.
+pub fn target_supports_std(target_tuple: &str) -> bool {
+    !(target_tuple.contains("-none")
+        || target_tuple.contains("nvptx")
+        || target_tuple.contains("switch"))
+}
diff --git a/src/doc/rustc-dev-guide/src/tests/directives.md b/src/doc/rustc-dev-guide/src/tests/directives.md
index f73a2811d5a..839076b809d 100644
--- a/src/doc/rustc-dev-guide/src/tests/directives.md
+++ b/src/doc/rustc-dev-guide/src/tests/directives.md
@@ -202,6 +202,7 @@ settings:
   `//@ needs-crate-type: cdylib, proc-macro` will cause the test to be ignored
   on `wasm32-unknown-unknown` target because the target does not support the
   `proc-macro` crate type.
+- `needs-target-std` — ignores if target platform does not have std support.
 
 The following directives will check LLVM support:
 
diff --git a/src/doc/rustc/src/platform-support/loongarch-none.md b/src/doc/rustc/src/platform-support/loongarch-none.md
index fd90b0a2763..7c3a7e6c8bc 100644
--- a/src/doc/rustc/src/platform-support/loongarch-none.md
+++ b/src/doc/rustc/src/platform-support/loongarch-none.md
@@ -11,8 +11,8 @@ Freestanding/bare-metal LoongArch binaries in ELF format: firmware, kernels, etc
 
 ## Target maintainers
 
-- [@heiher](https://github.com/heiher)
-- [@xen0n](https://github.com/xen0n)
+[@heiher](https://github.com/heiher)
+[@xen0n](https://github.com/xen0n)
 
 ## Requirements
 
diff --git a/src/tools/compiletest/src/directive-list.rs b/src/tools/compiletest/src/directive-list.rs
index 1406553c9ea..2ecb4fc8652 100644
--- a/src/tools/compiletest/src/directive-list.rs
+++ b/src/tools/compiletest/src/directive-list.rs
@@ -166,6 +166,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "needs-subprocess",
     "needs-symlink",
     "needs-target-has-atomic",
+    "needs-target-std",
     "needs-threads",
     "needs-unwind",
     "needs-wasmtime",
diff --git a/src/tools/compiletest/src/header/needs.rs b/src/tools/compiletest/src/header/needs.rs
index 2ace40c490b..b1165f4bb18 100644
--- a/src/tools/compiletest/src/header/needs.rs
+++ b/src/tools/compiletest/src/header/needs.rs
@@ -174,6 +174,11 @@ pub(super) fn handle_needs(
             condition: config.with_std_debug_assertions,
             ignore_reason: "ignored if std wasn't built with debug assertions",
         },
+        Need {
+            name: "needs-target-std",
+            condition: build_helper::targets::target_supports_std(&config.target),
+            ignore_reason: "ignored if target does not support std",
+        },
     ];
 
     let (name, rest) = match ln.split_once([':', ' ']) {
diff --git a/src/tools/compiletest/src/header/tests.rs b/src/tools/compiletest/src/header/tests.rs
index e7e5ff0ab00..31b49b09bcd 100644
--- a/src/tools/compiletest/src/header/tests.rs
+++ b/src/tools/compiletest/src/header/tests.rs
@@ -945,3 +945,14 @@ fn test_ignore_auxiliary() {
     let config = cfg().build();
     assert!(check_ignore(&config, "//@ ignore-auxiliary"));
 }
+
+#[test]
+fn test_needs_target_std() {
+    // Cherry-picks two targets:
+    // 1. `x86_64-unknown-none`: Tier 2, intentionally never supports std.
+    // 2. `x86_64-unknown-linux-gnu`: Tier 1, always supports std.
+    let config = cfg().target("x86_64-unknown-none").build();
+    assert!(check_ignore(&config, "//@ needs-target-std"));
+    let config = cfg().target("x86_64-unknown-linux-gnu").build();
+    assert!(!check_ignore(&config, "//@ needs-target-std"));
+}