add naked_functions_target_feature unstable feature

Author: folkertdev

compiler/rustc_feature/src/unstable.rs

@@ -568,6 +568,8 @@ declare_features! (
     (incomplete, mut_ref, "1.79.0", Some(123076)),
     /// Allows using `#[naked]` on functions.
     (unstable, naked_functions, "1.9.0", Some(90957)),
+    /// Allows using `#[target_feature(enable = "...")]` on `#[naked]` on functions.
+    (unstable, naked_functions_target_feature, "1.86.0", Some(138568)),
     /// Allows specifying the as-needed link modifier
     (unstable, native_link_modifiers_as_needed, "1.53.0", Some(81490)),
     /// Allow negative trait implementations.

compiler/rustc_passes/src/check_attr.rs

@@ -598,7 +598,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             sym::repr,
             // code generation
             sym::cold,
-            sym::target_feature,
             // documentation
             sym::doc,
         ];
@@ -624,6 +623,21 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         _ => {}
                     }
 
+                    if other_attr.has_name(sym::target_feature) {
+                        if !self.tcx.features().naked_functions_target_feature() {
+                            feature_err(
+                                &self.tcx.sess,
+                                sym::naked_functions_target_feature,
+                                other_attr.span(),
+                                "`#[target_feature(/* ... */)]` is currently unstable on `#[naked]` functions",
+                            ).emit();
+
+                            return;
+                        } else {
+                            continue;
+                        }
+                    }
+
                     if !ALLOW_LIST.iter().any(|name| other_attr.has_name(*name)) {
                         self.dcx().emit_err(errors::NakedFunctionIncompatibleAttribute {
                             span: other_attr.span(),

compiler/rustc_span/src/symbol.rs

@@ -1375,6 +1375,7 @@ symbols! {
         naked,
         naked_asm,
         naked_functions,
+        naked_functions_target_feature,
         name,
         names,
         native_link_modifiers,

tests/ui/asm/naked-functions-target-feature.rs

@@ -0,0 +1,21 @@
+//@ build-pass
+//@ needs-asm-support
+
+#![feature(naked_functions, naked_functions_target_feature)]
+#![crate_type = "lib"]
+
+use std::arch::{asm, naked_asm};
+
+#[cfg(target_arch = "x86_64")]
+#[target_feature(enable = "sse2")]
+#[naked]
+pub unsafe extern "C" fn compatible_target_feature() {
+    naked_asm!("");
+}
+
+#[cfg(target_arch = "aarch64")]
+#[target_feature(enable = "neon")]
+#[naked]
+pub unsafe extern "C" fn compatible_target_feature() {
+    naked_asm!("");
+}

tests/ui/asm/naked-functions.rs

@@ -230,13 +230,6 @@ pub unsafe extern "C" fn compatible_codegen_attributes() {
     naked_asm!("", options(raw));
 }
 
-#[cfg(target_arch = "x86_64")]
-#[target_feature(enable = "sse2")]
-#[naked]
-pub unsafe extern "C" fn compatible_target_feature() {
-    naked_asm!("");
-}
-
 #[doc = "foo bar baz"]
 /// a doc comment
 // a normal comment

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

@@ -0,0 +1,15 @@
+//@ needs-asm-support
+//@ only-x86_64
+
+#![feature(naked_functions)]
+
+use std::arch::naked_asm;
+
+#[naked]
+#[target_feature(enable = "avx2")]
+//~^ ERROR: `#[target_feature(/* ... */)]` is currently unstable on `#[naked]` functions
+extern "C" fn naked() {
+    unsafe { naked_asm!("") }
+}
+
+fn main() {}

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

@@ -0,0 +1,13 @@
+error[E0658]: `#[target_feature(/* ... */)]` is currently unstable on `#[naked]` functions
+  --> $DIR/feature-gate-naked_functions_target_feature.rs:8:1
+   |
+LL | #[target_feature(enable = "avx2")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #138568 <https://github.com/rust-lang/rust/issues/138568> for more information
+   = help: add `#![feature(naked_functions_target_feature)]` 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`.