Rollup merge of #147476 - ehuss:cold-attribute-test, r=chenyukang

Add a test for the cold attribute

This adds a test for the cold attribute to verify that it actually does something, and that it applies correctly in all the positions it is expected to work.

Author: matthiaskrgr

tests/codegen-llvm/cold-attribute.rs

@@ -0,0 +1,76 @@
+// Checks that the cold attribute adds the llvm cold attribute.
+//
+//@ reference: attributes.codegen.cold.intro
+//@ reference: attributes.codegen.cold.trait
+//@ edition:2024
+//@ compile-flags: -Copt-level=0
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: ; cold_attribute::free_function
+// CHECK-NEXT: Function Attrs: cold {{.*}}
+#[cold]
+pub fn free_function() {}
+
+// CHECK-LABEL: ; cold_attribute::async_block
+// CHECK-NEXT: Function Attrs: cold {{.*}}
+#[cold]
+pub async fn async_block() {
+    async fn x(f: impl Future<Output = ()>) {
+        f.await;
+    }
+    x(
+        // CHECK-LABEL: ; cold_attribute::async_block::{{{{closure}}}}::{{{{closure}}}}
+        // CHECK-NEXT: Function Attrs: cold {{.*}}
+        #[cold]
+        async {},
+    )
+    .await;
+}
+
+pub fn closure() {
+    fn x(f: impl Fn()) {
+        f()
+    }
+    x(
+        // CHECK-LABEL: ; cold_attribute::closure::{{{{closure}}}}
+        // CHECK-NEXT: Function Attrs: cold {{.*}}
+        #[cold]
+        || {},
+    );
+}
+
+pub struct S;
+
+impl S {
+    // CHECK-LABEL: ; cold_attribute::S::method
+    // CHECK-NEXT: Function Attrs: cold {{.*}}
+    #[cold]
+    pub fn method(&self) {}
+}
+
+pub trait Trait {
+    // CHECK-LABEL: ; cold_attribute::Trait::trait_fn
+    // CHECK-NEXT: Function Attrs: cold {{.*}}
+    #[cold]
+    fn trait_fn(&self) {}
+
+    #[cold]
+    fn trait_fn_overridden(&self) {}
+
+    fn impl_fn(&self);
+}
+
+impl Trait for S {
+    // CHECK-LABEL: ; <cold_attribute::S as cold_attribute::Trait>::impl_fn
+    // CHECK-NEXT: Function Attrs: cold {{.*}}
+    #[cold]
+    fn impl_fn(&self) {
+        self.trait_fn();
+    }
+
+    // This does not have #[cold], and does not inherit the cold attribute from the trait.
+    // CHECK-LABEL: ; <cold_attribute::S as cold_attribute::Trait>::trait_fn_overridden
+    // CHECK-NEXT: ; Function Attrs: uwtable
+    fn trait_fn_overridden(&self) {}
+}