Align attr fixes

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -4,7 +4,7 @@ use rustc_abi::{Align, ExternAbi};
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, attr};
 use rustc_attr_data_structures::{
-    AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, ReprAttr, UsedBy, find_attr,
+    AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, UsedBy, find_attr,
 };
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
@@ -109,14 +109,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
 
         if let hir::Attribute::Parsed(p) = attr {
             match p {
-                AttributeKind::Repr(reprs) => {
-                    codegen_fn_attrs.alignment = reprs
-                        .iter()
-                        .filter_map(
-                            |(r, _)| if let ReprAttr::ReprAlign(x) = r { Some(*x) } else { None },
-                        )
-                        .max();
-                }
                 AttributeKind::Cold(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
                 AttributeKind::ExportName { name, .. } => {
                     codegen_fn_attrs.export_name = Some(*name);

compiler/rustc_passes/messages.ftl

@@ -13,6 +13,10 @@ passes_abi_ne =
 passes_abi_of =
     fn_abi_of({$fn_name}) = {$fn_abi}
 
+passes_align_attr_application =
+    `#[align(...)]` should be applied to a function item
+    .label = not a function item
+
 passes_align_should_be_repr_align =
     `#[align(...)]` is not supported on {$item} items
     .suggestion = use `#[repr(align(...))]` instead

compiler/rustc_passes/src/check_attr.rs

@@ -1887,7 +1887,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     /// Checks if the `#[align]` attributes on `item` are valid.
     fn check_align(&self, span: Span, target: Target, align: Align, repr_span: Span) {
         match target {
-            Target::Fn | Target::Method(_) => {}
+            Target::Fn | Target::Method(_) | Target::ForeignFn => {}
             Target::Struct | Target::Union | Target::Enum => {
                 self.dcx().emit_err(errors::AlignShouldBeReprAlign {
                     span: repr_span,
@@ -1896,10 +1896,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 });
             }
             _ => {
-                self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
-                    hint_span: repr_span,
-                    span,
-                });
+                self.dcx().emit_err(errors::AlignAttrApplication { hint_span: repr_span, span });
             }
         }
 

compiler/rustc_passes/src/errors.rs

@@ -1838,3 +1838,12 @@ pub(crate) struct AlignShouldBeReprAlign {
     pub item: &'static str,
     pub align_bytes: u64,
 }
+
+#[derive(Diagnostic)]
+#[diag(passes_align_attr_application)]
+pub(crate) struct AlignAttrApplication {
+    #[primary_span]
+    pub hint_span: Span,
+    #[label]
+    pub span: Span,
+}

tests/codegen/align-fn.rs

@@ -1,4 +1,5 @@
 //@ compile-flags: -C no-prepopulate-passes -Z mir-opt-level=0 -Clink-dead-code
+//@ edition: 2024
 
 #![crate_type = "lib"]
 #![feature(fn_align)]
@@ -116,3 +117,23 @@ pub fn align_specified_twice_2() {}
 #[align(32)]
 #[align(256)]
 pub fn align_specified_twice_3() {}
+
+const _: () = {
+    // CHECK-LABEL: align_unmangled
+    // CHECK-SAME: align 256
+    #[unsafe(no_mangle)]
+    #[align(32)]
+    #[align(256)]
+    extern "C" fn align_unmangled() {}
+};
+
+unsafe extern "C" {
+    #[align(256)]
+    fn align_unmangled();
+}
+
+// CHECK-LABEL: async_align
+// CHECK-SAME: align 64
+#[unsafe(no_mangle)]
+#[align(64)]
+pub async fn async_align() {}

tests/ui/attributes/fn-align-dyn.rs

@@ -0,0 +1,15 @@
+//@ run-pass
+#![feature(fn_align)]
+
+trait Test {
+    #[align(4096)]
+    fn foo(&self);
+
+    #[align(4096)]
+    fn foo1(&self);
+}
+
+fn main() {
+    assert_eq!((<dyn Test>::foo as fn(_) as usize & !1) % 4096, 0);
+    assert_eq!((<dyn Test>::foo1 as fn(_) as usize & !1) % 4096, 0);
+}

tests/ui/attributes/malformed-fn-align.rs

@@ -23,3 +23,12 @@ fn f4() {}
 
 #[align(16)] //~ ERROR `#[align(...)]` is not supported on struct items
 struct S1;
+
+#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+const FOO: i32 = 42;
+
+#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+mod test {}
+
+#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+use ::std::iter;

tests/ui/attributes/malformed-fn-align.stderr

@@ -61,7 +61,31 @@ LL - #[align(16)]
 LL + #[repr(align(16))]
    |
 
-error: aborting due to 7 previous errors
+error: `#[align(...)]` should be applied to a function item
+  --> $DIR/malformed-fn-align.rs:27:1
+   |
+LL | #[align(32)]
+   | ^^^^^^^^^^^^
+LL | const FOO: i32 = 42;
+   | -------------------- not a function item
+
+error: `#[align(...)]` should be applied to a function item
+  --> $DIR/malformed-fn-align.rs:30:1
+   |
+LL | #[align(32)]
+   | ^^^^^^^^^^^^
+LL | mod test {}
+   | ----------- not a function item
+
+error: `#[align(...)]` should be applied to a function item
+  --> $DIR/malformed-fn-align.rs:33:1
+   |
+LL | #[align(32)]
+   | ^^^^^^^^^^^^
+LL | use ::std::iter;
+   | ---------------- not a function item
+
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0539, E0589, E0805.
 For more information about an error, try `rustc --explain E0539`.