Add kl and widekl target features, and the feature gate

Author: sayantn

compiler/rustc_feature/src/unstable.rs

@@ -525,6 +525,8 @@ declare_features! (
     (unstable, inline_const_pat, "1.58.0", Some(76001)),
     /// Allows using `pointer` and `reference` in intra-doc links
     (unstable, intra_doc_pointers, "1.51.0", Some(80896)),
+    // Allows using the `kl` and `widekl` target features and the associated intrinsics
+    (unstable, keylocker_x86, "CURRENT_RUSTC_VERSION", Some(134813)),
     // Allows setting the threshold for the `large_assignments` lint.
     (unstable, large_assignments, "1.52.0", Some(83518)),
     /// Allow to have type alias types for inter-crate use.

compiler/rustc_span/src/symbol.rs

@@ -1148,6 +1148,7 @@ symbols! {
         iterator,
         iterator_collect_fn,
         kcfi,
+        keylocker_x86,
         keyword,
         kind,
         kreg,

compiler/rustc_target/src/target_features.rs

@@ -508,6 +508,8 @@ const X86_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
     ("fma", STABLE, &["avx"]),
     ("fxsr", STABLE, &[]),
     ("gfni", unstable(sym::avx512_target_feature), &["sse2"]),
+    ("kl", unstable(sym::keylocker_x86), &["sse2"]),
+    ("widekl", unstable(sym::keylocker_x86), &["kl"]),
     ("lahfsahf", unstable(sym::lahfsahf_target_feature), &[]),
     ("lzcnt", STABLE, &[]),
     ("movbe", STABLE, &[]),

tests/ui/feature-gates/feature-gate-keylocker_x86.rs

@@ -0,0 +1,6 @@
+//@ only-x86_64
+#[target_feature(enable = "kl")]
+//~^ ERROR: currently unstable
+unsafe fn foo() {}
+
+fn main() {}

tests/ui/feature-gates/feature-gate-keylocker_x86.stderr

@@ -0,0 +1,13 @@
+rror[E0658]: the target feature `kl` is currently unstable
+  --> $DIR/feature-gate-keylocker_x86.rs:2:18
+   |
+LL | #[target_feature(enable = "kl")]
+   |                  ^^^^^^^^^^^^^
+   |
+   = note: see issue #134813 <https://github.com/rust-lang/rust/issues/134813> for more information
+   = help: add `#![feature(keylocker_x86)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.