add `#[align]` attribute

Right now it's used for functions with `fn_align`, in the future it will
get more uses (statics, struct fields, etc.)

30 files changed, 320 insertions, 133 deletions

diff --git a/compiler/rustc_attr_data_structures/src/attributes.rs b/compiler/rustc_attr_data_structures/src/attributes.rs
index d4c43456049..cdc01dc6c91 100644
--- a/compiler/rustc_attr_data_structures/src/attributes.rs
+++ b/compiler/rustc_attr_data_structures/src/attributes.rs
@@ -182,6 +182,9 @@ impl Deprecation {
 #[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable, PrintAttribute)]
 pub enum AttributeKind {
     // tidy-alphabetical-start
+    /// Represents `#[align(N)]`.
+    Align { align: Align, span: Span },
+
     /// Represents `#[rustc_allow_const_fn_unstable]`.
     AllowConstFnUnstable(ThinVec<Symbol>),
 
diff --git a/compiler/rustc_attr_parsing/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index b9b386635f6..0891afc003e 100644
--- a/compiler/rustc_attr_parsing/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -44,6 +44,9 @@ attr_parsing_incorrect_repr_format_packed_expect_integer =
 attr_parsing_incorrect_repr_format_packed_one_or_zero_arg =
     incorrect `repr(packed)` attribute format: `packed` takes exactly one parenthesized argument, or no parentheses at all
 
+attr_parsing_invalid_alignment_value =
+    invalid alignment value: {$error_part}
+
 attr_parsing_invalid_issue_string =
     `issue` must be a non-zero numeric string or "none"
     .must_not_be_zero = `issue` must not be "0", use "none" instead
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
index ae9e7871874..c9f9f34bdb7 100644
--- a/compiler/rustc_attr_parsing/src/attributes/repr.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -4,7 +4,7 @@ use rustc_attr_data_structures::{AttributeKind, IntType, ReprAttr};
 use rustc_feature::{AttributeTemplate, template};
 use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 
-use super::{CombineAttributeParser, ConvertFn};
+use super::{AcceptMapping, AttributeParser, CombineAttributeParser, ConvertFn, FinalizeContext};
 use crate::context::{AcceptContext, Stage};
 use crate::parser::{ArgParser, MetaItemListParser, MetaItemParser};
 use crate::session_diagnostics;
@@ -203,7 +203,7 @@ fn parse_repr_align<S: Stage>(
                 });
             }
             Align => {
-                cx.dcx().emit_err(session_diagnostics::IncorrectReprFormatAlignOneArg {
+                cx.emit_err(session_diagnostics::IncorrectReprFormatAlignOneArg {
                     span: param_span,
                 });
             }
@@ -266,3 +266,57 @@ fn parse_alignment(node: &LitKind) -> Result<Align, &'static str> {
         Err("not an unsuffixed integer")
     }
 }
+
+/// Parse #[align(N)].
+#[derive(Default)]
+pub(crate) struct AlignParser(Option<(Align, Span)>);
+
+impl AlignParser {
+    const PATH: &'static [Symbol] = &[sym::align];
+    const TEMPLATE: AttributeTemplate = template!(Word, List: "<alignment in bytes>");
+
+    fn parse<'c, S: Stage>(
+        &mut self,
+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) {
+        match args {
+            ArgParser::NoArgs | ArgParser::NameValue(_) => {
+                cx.expected_list(cx.attr_span);
+            }
+            ArgParser::List(list) => {
+                let Some(align) = list.single() else {
+                    cx.expected_single_argument(list.span);
+                    return;
+                };
+
+                let Some(lit) = align.lit() else {
+                    cx.emit_err(session_diagnostics::IncorrectReprFormatExpectInteger {
+                        span: align.span(),
+                    });
+
+                    return;
+                };
+
+                match parse_alignment(&lit.kind) {
+                    Ok(literal) => self.0 = Ord::max(self.0, Some((literal, cx.attr_span))),
+                    Err(message) => {
+                        cx.emit_err(session_diagnostics::InvalidAlignmentValue {
+                            span: lit.span,
+                            error_part: message,
+                        });
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl<S: Stage> AttributeParser<S> for AlignParser {
+    const ATTRIBUTES: AcceptMapping<Self, S> = &[(Self::PATH, Self::TEMPLATE, Self::parse)];
+
+    fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
+        let (align, span) = self.0?;
+        Some(AttributeKind::Align { align, span })
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 51c1760da30..d7570634c1f 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -19,7 +19,7 @@ use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
 use crate::attributes::lint_helpers::AsPtrParser;
-use crate::attributes::repr::ReprParser;
+use crate::attributes::repr::{AlignParser, ReprParser};
 use crate::attributes::stability::{
     BodyStabilityParser, ConstStabilityIndirectParser, ConstStabilityParser, StabilityParser,
 };
@@ -90,6 +90,7 @@ macro_rules! attribute_parsers {
 attribute_parsers!(
     pub(crate) static ATTRIBUTE_PARSERS = [
         // tidy-alphabetical-start
+        AlignParser,
         BodyStabilityParser,
         ConfusablesParser,
         ConstStabilityParser,
diff --git a/compiler/rustc_attr_parsing/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
index 57ac92a0ca1..337921a318c 100644
--- a/compiler/rustc_attr_parsing/src/session_diagnostics.rs
+++ b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -451,6 +451,14 @@ pub(crate) struct EmptyConfusables {
 }
 
 #[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_alignment_value, code = E0589)]
+pub(crate) struct InvalidAlignmentValue {
+    #[primary_span]
+    pub span: Span,
+    pub error_part: &'static str,
+}
+
+#[derive(Diagnostic)]
 #[diag(attr_parsing_repr_ident, code = E0565)]
 pub(crate) struct ReprIdent {
     #[primary_span]
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 188a9a98ce7..98742255063 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -3,7 +3,6 @@ use std::str::FromStr;
 use rustc_abi::ExternAbi;
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, attr};
-use rustc_attr_data_structures::ReprAttr::ReprAlign;
 use rustc_attr_data_structures::{
     AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, find_attr,
 };
@@ -110,17 +109,8 @@ 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 ReprAlign(x) = r { Some(*x) } else { None })
-                        .max();
-                }
-
-                _ => {}
-            }
+        if let hir::Attribute::Parsed(AttributeKind::Align { align, .. }) = attr {
+            codegen_fn_attrs.alignment = Some(*align);
         }
 
         let Some(Ident { name, .. }) = attr.ident() else {
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index b5218ec267c..5b1f1684d54 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -495,6 +495,7 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ),
     ungated!(no_link, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
     ungated!(repr, Normal, template!(List: "C"), DuplicatesOk, EncodeCrossCrate::No),
+    gated!(align, Normal, template!(List: "alignment"), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(align)),
     ungated!(unsafe(Edition2024) export_name, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
     ungated!(unsafe(Edition2024) link_section, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
     ungated!(unsafe(Edition2024) no_mangle, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index f21cf5fa45e..2f16d385efb 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -47,8 +47,7 @@ pub struct CodegenFnAttrs {
     /// be generated against a specific instruction set. Only usable on architectures which allow
     /// switching between multiple instruction sets.
     pub instruction_set: Option<InstructionSetAttr>,
-    /// The `#[repr(align(...))]` attribute. Indicates the value of which the function should be
-    /// aligned to.
+    /// The `#[align(...)]` attribute. Determines the alignment of the function body.
     pub alignment: Option<Align>,
     /// The `#[patchable_function_entry(...)]` attribute. Indicates how many nops should be around
     /// the function entry.
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index b3096e46b09..a12215a44f9 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -289,6 +289,7 @@ fn emit_malformed_attribute(
             | sym::rustc_force_inline
             | sym::rustc_confusables
             | sym::repr
+            | sym::align
             | sym::deprecated
     ) {
         return;
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 7c237d708c0..c1a2b3b2973 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -13,6 +13,10 @@ passes_abi_ne =
 passes_abi_of =
     fn_abi_of({$fn_name}) = {$fn_abi}
 
+passes_align_should_be_repr_align =
+    `#[align(...)]` is not supported on {$item} items
+    .suggestion = use `#[repr(align(...))]` instead
+
 passes_allow_incoherent_impl =
     `rustc_allow_incoherent_impl` attribute should be applied to impl items
     .label = the only currently supported targets are inherent methods
@@ -29,10 +33,6 @@ passes_attr_application_struct =
     attribute should be applied to a struct
     .label = not a struct
 
-passes_attr_application_struct_enum_function_method_union =
-    attribute should be applied to a struct, enum, function, associated function, or union
-    .label = not a struct, enum, function, associated function, or union
-
 passes_attr_application_struct_enum_union =
     attribute should be applied to a struct, enum, or union
     .label = not a struct, enum, or union
@@ -583,13 +583,14 @@ passes_remove_fields =
      *[other] fields
     }
 
-passes_repr_align_function =
-    `repr(align)` attributes on functions are unstable
-
 passes_repr_align_greater_than_target_max =
     alignment must not be greater than `isize::MAX` bytes
     .note = `isize::MAX` is {$size} for the current target
 
+passes_repr_align_should_be_align =
+    `#[repr(align(...))]` is not supported on {$item} items
+    .help = use `#[align(...)]` instead
+
 passes_repr_conflicting =
     conflicting representation hints
 
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 5ce803aa1f8..50d6c5d9764 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -146,6 +146,10 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
                 Attribute::Parsed(AttributeKind::Repr(_)) => { /* handled below this loop and elsewhere */
                 }
+                Attribute::Parsed(AttributeKind::Align { align, span: repr_span }) => {
+                    self.check_align(span, target, *align, *repr_span)
+                }
+
                 Attribute::Parsed(
                     AttributeKind::BodyStability { .. }
                     | AttributeKind::ConstStabilityIndirect
@@ -643,6 +647,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             sym::naked,
             sym::instruction_set,
             sym::repr,
+            sym::align,
             sym::rustc_std_internal_symbol,
             // code generation
             sym::cold,
@@ -679,7 +684,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     // this check can be part of the parser and be removed here
                     match other_attr {
                         Attribute::Parsed(
-                            AttributeKind::Deprecation { .. } | AttributeKind::Repr { .. },
+                            AttributeKind::Deprecation { .. }
+                            | AttributeKind::Repr { .. }
+                            | AttributeKind::Align { .. },
                         ) => {
                             continue;
                         }
@@ -1964,6 +1971,28 @@ 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::Struct | Target::Union | Target::Enum => {
+                self.dcx().emit_err(errors::AlignShouldBeReprAlign {
+                    span: repr_span,
+                    item: target.name(),
+                    align_bytes: align.bytes(),
+                });
+            }
+            _ => {
+                self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
+                    hint_span: repr_span,
+                    span,
+                });
+            }
+        }
+
+        self.check_align_value(align, repr_span);
+    }
+
     /// Checks if the `#[repr]` attributes on `item` are valid.
     fn check_repr(
         &self,
@@ -2016,23 +2045,16 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     match target {
                         Target::Struct | Target::Union | Target::Enum => {}
                         Target::Fn | Target::Method(_) => {
-                            if !self.tcx.features().fn_align() {
-                                feature_err(
-                                    &self.tcx.sess,
-                                    sym::fn_align,
-                                    *repr_span,
-                                    fluent::passes_repr_align_function,
-                                )
-                                .emit();
-                            }
+                            self.dcx().emit_err(errors::ReprAlignShouldBeAlign {
+                                span: *repr_span,
+                                item: target.name(),
+                            });
                         }
                         _ => {
-                            self.dcx().emit_err(
-                                errors::AttrApplication::StructEnumFunctionMethodUnion {
-                                    hint_span: *repr_span,
-                                    span,
-                                },
-                            );
+                            self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
+                                hint_span: *repr_span,
+                                span,
+                            });
                         }
                     }
 
@@ -2090,21 +2112,16 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         match target {
                             Target::Struct | Target::Union | Target::Enum => continue,
                             Target::Fn | Target::Method(_) => {
-                                feature_err(
-                                    &self.tcx.sess,
-                                    sym::fn_align,
-                                    *repr_span,
-                                    fluent::passes_repr_align_function,
-                                )
-                                .emit();
+                                self.dcx().emit_err(errors::ReprAlignShouldBeAlign {
+                                    span: *repr_span,
+                                    item: target.name(),
+                                });
                             }
                             _ => {
-                                self.dcx().emit_err(
-                                    errors::AttrApplication::StructEnumFunctionMethodUnion {
-                                        hint_span: *repr_span,
-                                        span,
-                                    },
-                                );
+                                self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
+                                    hint_span: *repr_span,
+                                    span,
+                                });
                             }
                         }
                     }
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index f0d4b610f63..587d9170f06 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -1308,13 +1308,6 @@ pub(crate) enum AttrApplication {
         #[label]
         span: Span,
     },
-    #[diag(passes_attr_application_struct_enum_function_method_union, code = E0517)]
-    StructEnumFunctionMethodUnion {
-        #[primary_span]
-        hint_span: Span,
-        #[label]
-        span: Span,
-    },
 }
 
 #[derive(Diagnostic)]
@@ -1816,3 +1809,26 @@ pub(crate) enum UnexportableItem<'a> {
         field_name: &'a str,
     },
 }
+
+#[derive(Diagnostic)]
+#[diag(passes_repr_align_should_be_align)]
+pub(crate) struct ReprAlignShouldBeAlign {
+    #[primary_span]
+    #[help]
+    pub span: Span,
+    pub item: &'static str,
+}
+
+#[derive(Diagnostic)]
+#[diag(passes_align_should_be_repr_align)]
+pub(crate) struct AlignShouldBeReprAlign {
+    #[primary_span]
+    #[suggestion(
+        style = "verbose",
+        applicability = "machine-applicable",
+        code = "#[repr(align({align_bytes}))]"
+    )]
+    pub span: Span,
+    pub item: &'static str,
+    pub align_bytes: u64,
+}
diff --git a/src/tools/miri/tests/pass/fn_align.rs b/src/tools/miri/tests/pass/fn_align.rs
index 550bb1cb4d7..28f92995880 100644
--- a/src/tools/miri/tests/pass/fn_align.rs
+++ b/src/tools/miri/tests/pass/fn_align.rs
@@ -1,21 +1,21 @@
 //@compile-flags: -Zmin-function-alignment=8
 #![feature(fn_align)]
 
-// When a function uses `repr(align(N))`, the function address should be a multiple of `N`.
+// When a function uses `align(N)`, the function address should be a multiple of `N`.
 
-#[repr(align(256))]
+#[align(256)]
 fn foo() {}
 
-#[repr(align(16))]
+#[align(16)]
 fn bar() {}
 
-#[repr(align(4))]
+#[align(4)]
 fn baz() {}
 
 fn main() {
     assert!((foo as usize).is_multiple_of(256));
     assert!((bar as usize).is_multiple_of(16));
 
-    // The maximum of `repr(align(N))` and `-Zmin-function-alignment=N` is used.
+    // The maximum of `align(N)` and `-Zmin-function-alignment=N` is used.
     assert!((baz as usize).is_multiple_of(8));
 }
diff --git a/tests/assembly/naked-functions/wasm32.rs b/tests/assembly/naked-functions/wasm32.rs
index 984152f2b45..5f114246ad5 100644
--- a/tests/assembly/naked-functions/wasm32.rs
+++ b/tests/assembly/naked-functions/wasm32.rs
@@ -37,7 +37,7 @@ extern "C" fn nop() {
 #[unsafe(naked)]
 #[linkage = "weak"]
 // wasm functions cannot be aligned, so this has no effect
-#[repr(align(32))]
+#[align(32)]
 extern "C" fn weak_aligned_nop() {
     naked_asm!("nop")
 }
diff --git a/tests/codegen/align-fn.rs b/tests/codegen/align-fn.rs
index 660d8cd2bbf..267da060240 100644
--- a/tests/codegen/align-fn.rs
+++ b/tests/codegen/align-fn.rs
@@ -5,7 +5,7 @@
 
 // CHECK: align 16
 #[no_mangle]
-#[repr(align(16))]
+#[align(16)]
 pub fn fn_align() {}
 
 pub struct A;
@@ -13,12 +13,12 @@ pub struct A;
 impl A {
     // CHECK: align 16
     #[no_mangle]
-    #[repr(align(16))]
+    #[align(16)]
     pub fn method_align(self) {}
 
     // CHECK: align 16
     #[no_mangle]
-    #[repr(align(16))]
+    #[align(16)]
     pub fn associated_fn() {}
 }
 
@@ -26,19 +26,19 @@ trait T: Sized {
     fn trait_fn() {}
 
     // CHECK: align 32
-    #[repr(align(32))]
+    #[align(32)]
     fn trait_method(self) {}
 }
 
 impl T for A {
     // CHECK: align 16
     #[no_mangle]
-    #[repr(align(16))]
+    #[align(16)]
     fn trait_fn() {}
 
     // CHECK: align 16
     #[no_mangle]
-    #[repr(align(16))]
+    #[align(16)]
     fn trait_method(self) {}
 }
 
@@ -51,18 +51,20 @@ pub fn foo() {
 // CHECK-LABEL: align_specified_twice_1
 // CHECK-SAME: align 64
 #[no_mangle]
-#[repr(align(32), align(64))]
+#[align(32)]
+#[align(64)]
 pub fn align_specified_twice_1() {}
 
 // CHECK-LABEL: align_specified_twice_2
 // CHECK-SAME: align 128
 #[no_mangle]
-#[repr(align(128), align(32))]
+#[align(128)]
+#[align(32)]
 pub fn align_specified_twice_2() {}
 
 // CHECK-LABEL: align_specified_twice_3
 // CHECK-SAME: align 256
 #[no_mangle]
-#[repr(align(32))]
-#[repr(align(256))]
+#[align(32)]
+#[align(256)]
 pub fn align_specified_twice_3() {}
diff --git a/tests/codegen/min-function-alignment.rs b/tests/codegen/min-function-alignment.rs
index 7c0ad12402a..75f845572a4 100644
--- a/tests/codegen/min-function-alignment.rs
+++ b/tests/codegen/min-function-alignment.rs
@@ -18,16 +18,16 @@ pub fn no_explicit_align() {}
 // align16: align 16
 // align1024: align 1024
 #[no_mangle]
-#[repr(align(8))]
+#[align(8)]
 pub fn lower_align() {}
 
-// the higher value of min-function-alignment and repr(align) wins out
+// the higher value of min-function-alignment and the align attribute wins out
 //
 // CHECK-LABEL: @higher_align
 // align16: align 32
 // align1024: align 1024
 #[no_mangle]
-#[repr(align(32))]
+#[align(32)]
 pub fn higher_align() {}
 
 // cold functions follow the same rules as other functions
diff --git a/tests/codegen/naked-fn/aligned.rs b/tests/codegen/naked-fn/aligned.rs
index 47ef779f1b2..f9fce8e5a5d 100644
--- a/tests/codegen/naked-fn/aligned.rs
+++ b/tests/codegen/naked-fn/aligned.rs
@@ -8,7 +8,7 @@ use std::arch::naked_asm;
 
 // CHECK: .balign 16
 // CHECK-LABEL: naked_empty:
-#[repr(align(16))]
+#[align(16)]
 #[no_mangle]
 #[unsafe(naked)]
 pub extern "C" fn naked_empty() {
diff --git a/tests/codegen/naked-fn/min-function-alignment.rs b/tests/codegen/naked-fn/min-function-alignment.rs
index 1d778be8c90..59554c1cae5 100644
--- a/tests/codegen/naked-fn/min-function-alignment.rs
+++ b/tests/codegen/naked-fn/min-function-alignment.rs
@@ -16,7 +16,7 @@ pub extern "C" fn naked_no_explicit_align() {
 
 // CHECK: .balign 16
 #[no_mangle]
-#[repr(align(8))]
+#[align(8)]
 #[unsafe(naked)]
 pub extern "C" fn naked_lower_align() {
     core::arch::naked_asm!("ret")
@@ -24,7 +24,7 @@ pub extern "C" fn naked_lower_align() {
 
 // CHECK: .balign 32
 #[no_mangle]
-#[repr(align(32))]
+#[align(32)]
 #[unsafe(naked)]
 pub extern "C" fn naked_higher_align() {
     core::arch::naked_asm!("ret")
diff --git a/tests/ui/asm/naked-with-invalid-repr-attr.rs b/tests/ui/asm/naked-with-invalid-repr-attr.rs
index 96eed70dc55..bfbbf29a69e 100644
--- a/tests/ui/asm/naked-with-invalid-repr-attr.rs
+++ b/tests/ui/asm/naked-with-invalid-repr-attr.rs
@@ -19,8 +19,9 @@ extern "C" fn example2() {
     naked_asm!("")
 }
 
-#[repr(align(16), C)]
+#[repr(C)]
 //~^ ERROR attribute should be applied to a struct, enum, or union [E0517]
+#[align(16)]
 #[unsafe(naked)]
 extern "C" fn example3() {
     //~^ NOTE not a struct, enum, or union
diff --git a/tests/ui/asm/naked-with-invalid-repr-attr.stderr b/tests/ui/asm/naked-with-invalid-repr-attr.stderr
index f173a39e5bf..4eb4a4e5a04 100644
--- a/tests/ui/asm/naked-with-invalid-repr-attr.stderr
+++ b/tests/ui/asm/naked-with-invalid-repr-attr.stderr
@@ -23,10 +23,10 @@ LL | | }
    | |_- not a struct, enum, or union
 
 error[E0517]: attribute should be applied to a struct, enum, or union
-  --> $DIR/naked-with-invalid-repr-attr.rs:22:19
+  --> $DIR/naked-with-invalid-repr-attr.rs:22:8
    |
-LL |   #[repr(align(16), C)]
-   |                     ^
+LL |   #[repr(C)]
+   |          ^
 ...
 LL | / extern "C" fn example3() {
 LL | |
@@ -35,7 +35,7 @@ LL | | }
    | |_- not a struct, enum, or union
 
 error[E0517]: attribute should be applied to a struct, enum, or union
-  --> $DIR/naked-with-invalid-repr-attr.rs:31:8
+  --> $DIR/naked-with-invalid-repr-attr.rs:32:8
    |
 LL |   #[repr(C, packed)]
    |          ^
@@ -48,7 +48,7 @@ LL | | }
    | |_- not a struct, enum, or union
 
 error[E0517]: attribute should be applied to a struct or union
-  --> $DIR/naked-with-invalid-repr-attr.rs:31:11
+  --> $DIR/naked-with-invalid-repr-attr.rs:32:11
    |
 LL |   #[repr(C, packed)]
    |             ^^^^^^
@@ -61,7 +61,7 @@ LL | | }
    | |_- not a struct or union
 
 error[E0517]: attribute should be applied to an enum
-  --> $DIR/naked-with-invalid-repr-attr.rs:41:8
+  --> $DIR/naked-with-invalid-repr-attr.rs:42:8
    |
 LL |   #[repr(u8)]
    |          ^^
diff --git a/tests/ui/attributes/arg-error-issue-121425.stderr b/tests/ui/attributes/arg-error-issue-121425.stderr
index 6e71f15fdc8..1beb99b1703 100644
--- a/tests/ui/attributes/arg-error-issue-121425.stderr
+++ b/tests/ui/attributes/arg-error-issue-121425.stderr
@@ -1,9 +1,3 @@
-error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
-  --> $DIR/arg-error-issue-121425.rs:16:8
-   |
-LL | #[repr(align())]
-   |        ^^^^^^^
-
 error[E0693]: incorrect `repr(align)` attribute format: `align` expects a literal integer as argument
   --> $DIR/arg-error-issue-121425.rs:4:14
    |
@@ -22,6 +16,12 @@ error[E0589]: invalid `repr(align)` attribute: not an unsuffixed integer
 LL | #[repr(align("str"))]
    |              ^^^^^
 
+error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
+  --> $DIR/arg-error-issue-121425.rs:16:8
+   |
+LL | #[repr(align())]
+   |        ^^^^^^^
+
 error[E0552]: incorrect `repr(packed)` attribute format: `packed` expects a literal integer as argument
   --> $DIR/arg-error-issue-121425.rs:21:15
    |
diff --git a/tests/ui/attributes/invalid-repr.rs b/tests/ui/attributes/invalid-repr.rs
index 10a487c127e..d7933533405 100644
--- a/tests/ui/attributes/invalid-repr.rs
+++ b/tests/ui/attributes/invalid-repr.rs
@@ -1,5 +1,5 @@
 #[repr(align(16))]
-//~^ ERROR attribute should be applied to a struct, enum, function, associated function, or union
+//~^ ERROR attribute should be applied to a struct, enum, or union
 pub type Foo = i32;
 
 fn main() {}
diff --git a/tests/ui/attributes/invalid-repr.stderr b/tests/ui/attributes/invalid-repr.stderr
index 681460ad081..3f5a305c6b7 100644
--- a/tests/ui/attributes/invalid-repr.stderr
+++ b/tests/ui/attributes/invalid-repr.stderr
@@ -1,11 +1,11 @@
-error[E0517]: attribute should be applied to a struct, enum, function, associated function, or union
+error[E0517]: attribute should be applied to a struct, enum, or union
   --> $DIR/invalid-repr.rs:1:8
    |
 LL | #[repr(align(16))]
    |        ^^^^^^^^^
 LL |
 LL | pub type Foo = i32;
-   | ------------------- not a struct, enum, function, associated function, or union
+   | ------------------- not a struct, enum, or union
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/attributes/malformed-fn-align.rs b/tests/ui/attributes/malformed-fn-align.rs
index 4aaad01b723..35ffd6d8acc 100644
--- a/tests/ui/attributes/malformed-fn-align.rs
+++ b/tests/ui/attributes/malformed-fn-align.rs
@@ -2,6 +2,21 @@
 #![crate_type = "lib"]
 
 trait MyTrait {
-    #[repr(align)] //~ ERROR invalid `repr(align)` attribute: `align` needs an argument
+    #[align] //~ ERROR malformed `align` attribute input
     fn myfun();
 }
+
+#[align = 16] //~ ERROR malformed `align` attribute input
+fn f1() {}
+
+#[align("hello")] //~ ERROR invalid alignment value: not an unsuffixed integer
+fn f2() {}
+
+#[align(0)] //~ ERROR invalid alignment value: not a power of two
+fn f3() {}
+
+#[repr(align(16))] //~ ERROR `#[repr(align(...))]` is not supported on function items
+fn f4() {}
+
+#[align(16)] //~ ERROR `#[align(...)]` is not supported on struct items
+struct S1;
diff --git a/tests/ui/attributes/malformed-fn-align.stderr b/tests/ui/attributes/malformed-fn-align.stderr
index 57913c48ef7..765255c2c3a 100644
--- a/tests/ui/attributes/malformed-fn-align.stderr
+++ b/tests/ui/attributes/malformed-fn-align.stderr
@@ -1,9 +1,66 @@
-error[E0589]: invalid `repr(align)` attribute: `align` needs an argument
-  --> $DIR/malformed-fn-align.rs:5:12
+error[E0539]: malformed `align` attribute input
+  --> $DIR/malformed-fn-align.rs:5:5
+   |
+LL |     #[align]
+   |     ^^^^^^^^ expected this to be a list
+   |
+help: try changing it to one of the following valid forms of the attribute
+   |
+LL |     #[align(<alignment in bytes>)]
+   |            ++++++++++++++++++++++
+
+error[E0539]: malformed `align` attribute input
+  --> $DIR/malformed-fn-align.rs:9:1
+   |
+LL | #[align = 16]
+   | ^^^^^^^^^^^^^ expected this to be a list
+   |
+help: try changing it to one of the following valid forms of the attribute
+   |
+LL - #[align = 16]
+LL + #[align(<alignment in bytes>)]
+   |
+LL - #[align = 16]
+LL + #[align]
+   |
+
+error[E0589]: invalid alignment value: not an unsuffixed integer
+  --> $DIR/malformed-fn-align.rs:12:9
+   |
+LL | #[align("hello")]
+   |         ^^^^^^^
+
+error[E0589]: invalid alignment value: not a power of two
+  --> $DIR/malformed-fn-align.rs:15:9
+   |
+LL | #[align(0)]
+   |         ^
+
+error: `#[repr(align(...))]` is not supported on function items
+  --> $DIR/malformed-fn-align.rs:18:8
+   |
+LL | #[repr(align(16))]
+   |        ^^^^^^^^^
+   |
+help: use `#[align(...)]` instead
+  --> $DIR/malformed-fn-align.rs:18:8
+   |
+LL | #[repr(align(16))]
+   |        ^^^^^^^^^
+
+error: `#[align(...)]` is not supported on struct items
+  --> $DIR/malformed-fn-align.rs:21:1
+   |
+LL | #[align(16)]
+   | ^^^^^^^^^^^^
+   |
+help: use `#[repr(align(...))]` instead
+   |
+LL - #[align(16)]
+LL + #[repr(align(16))]
    |
-LL |     #[repr(align)]
-   |            ^^^^^ help: supply an argument here: `align(...)`
 
-error: aborting due to 1 previous error
+error: aborting due to 6 previous errors
 
-For more information about this error, try `rustc --explain E0589`.
+Some errors have detailed explanations: E0539, E0589.
+For more information about an error, try `rustc --explain E0539`.
diff --git a/tests/ui/feature-gates/feature-gate-fn_align.rs b/tests/ui/feature-gates/feature-gate-fn_align.rs
index 744877704dd..b6c300e5cbe 100644
--- a/tests/ui/feature-gates/feature-gate-fn_align.rs
+++ b/tests/ui/feature-gates/feature-gate-fn_align.rs
@@ -1,9 +1,12 @@
 #![crate_type = "lib"]
 
-#[repr(align(16))] //~ ERROR `repr(align)` attributes on functions are unstable
+#[align(16)]
+//~^ ERROR the `#[align]` attribute is an experimental feature
 fn requires_alignment() {}
 
 trait MyTrait {
-    #[repr(align)] //~ ERROR invalid `repr(align)` attribute: `align` needs an argument
+    #[align]
+    //~^ ERROR the `#[align]` attribute is an experimental feature
+    //~| ERROR malformed `align` attribute input
     fn myfun();
 }
diff --git a/tests/ui/feature-gates/feature-gate-fn_align.stderr b/tests/ui/feature-gates/feature-gate-fn_align.stderr
index ff17c29fe02..93ef136dc73 100644
--- a/tests/ui/feature-gates/feature-gate-fn_align.stderr
+++ b/tests/ui/feature-gates/feature-gate-fn_align.stderr
@@ -1,20 +1,35 @@
-error[E0589]: invalid `repr(align)` attribute: `align` needs an argument
-  --> $DIR/feature-gate-fn_align.rs:7:12
+error[E0658]: the `#[align]` attribute is an experimental feature
+  --> $DIR/feature-gate-fn_align.rs:3:1
    |
-LL |     #[repr(align)]
-   |            ^^^^^ help: supply an argument here: `align(...)`
+LL | #[align(16)]
+   | ^^^^^^^^^^^^
+   |
+   = note: see issue #82232 <https://github.com/rust-lang/rust/issues/82232> for more information
+   = help: add `#![feature(fn_align)]` 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[E0658]: `repr(align)` attributes on functions are unstable
-  --> $DIR/feature-gate-fn_align.rs:3:8
+error[E0658]: the `#[align]` attribute is an experimental feature
+  --> $DIR/feature-gate-fn_align.rs:8:5
    |
-LL | #[repr(align(16))]
-   |        ^^^^^^^^^
+LL |     #[align]
+   |     ^^^^^^^^
    |
    = note: see issue #82232 <https://github.com/rust-lang/rust/issues/82232> for more information
    = help: add `#![feature(fn_align)]` 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 2 previous errors
+error[E0539]: malformed `align` attribute input
+  --> $DIR/feature-gate-fn_align.rs:8:5
+   |
+LL |     #[align]
+   |     ^^^^^^^^ expected this to be a list
+   |
+help: try changing it to one of the following valid forms of the attribute
+   |
+LL |     #[align(<alignment in bytes>)]
+   |            ++++++++++++++++++++++
+
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0589, E0658.
-For more information about an error, try `rustc --explain E0589`.
+Some errors have detailed explanations: E0539, E0658.
+For more information about an error, try `rustc --explain E0539`.
diff --git a/tests/ui/repr/attr-usage-repr.rs b/tests/ui/repr/attr-usage-repr.rs
index cbf99f16e03..ca63ac564fc 100644
--- a/tests/ui/repr/attr-usage-repr.rs
+++ b/tests/ui/repr/attr-usage-repr.rs
@@ -45,7 +45,7 @@ enum EInt {
     B,
 }
 
-#[repr()] //~ ERROR attribute should be applied to a struct, enum, function, associated function, or union [E0517]
+#[repr()] //~ ERROR attribute should be applied to a struct, enum, or union [E0517]
 type SirThisIsAType = i32;
 
 #[repr()]
diff --git a/tests/ui/repr/attr-usage-repr.stderr b/tests/ui/repr/attr-usage-repr.stderr
index a25e68c483f..a62992c597a 100644
--- a/tests/ui/repr/attr-usage-repr.stderr
+++ b/tests/ui/repr/attr-usage-repr.stderr
@@ -36,13 +36,13 @@ LL | |     B,
 LL | | }
    | |_- not a struct
 
-error[E0517]: attribute should be applied to a struct, enum, function, associated function, or union
+error[E0517]: attribute should be applied to a struct, enum, or union
   --> $DIR/attr-usage-repr.rs:48:1
    |
 LL | #[repr()]
    | ^^^^^^^^^
 LL | type SirThisIsAType = i32;
-   | -------------------------- not a struct, enum, function, associated function, or union
+   | -------------------------- not a struct, enum, or union
 
 error: aborting due to 5 previous errors
 
diff --git a/tests/ui/repr/malformed-repr-hints.stderr b/tests/ui/repr/malformed-repr-hints.stderr
index 7a6e9ccc73e..6fb92755761 100644
--- a/tests/ui/repr/malformed-repr-hints.stderr
+++ b/tests/ui/repr/malformed-repr-hints.stderr
@@ -1,15 +1,3 @@
-error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
-  --> $DIR/malformed-repr-hints.rs:14:8
-   |
-LL | #[repr(align(2, 4))]
-   |        ^^^^^^^^^^^
-
-error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
-  --> $DIR/malformed-repr-hints.rs:18:8
-   |
-LL | #[repr(align())]
-   |        ^^^^^^^
-
 error[E0552]: incorrect `repr(packed)` attribute format: `packed` takes exactly one parenthesized argument, or no parentheses at all
   --> $DIR/malformed-repr-hints.rs:6:8
    |
@@ -22,6 +10,18 @@ error[E0589]: invalid `repr(align)` attribute: `align` needs an argument
 LL | #[repr(align)]
    |        ^^^^^ help: supply an argument here: `align(...)`
 
+error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
+  --> $DIR/malformed-repr-hints.rs:14:8
+   |
+LL | #[repr(align(2, 4))]
+   |        ^^^^^^^^^^^
+
+error[E0693]: incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
+  --> $DIR/malformed-repr-hints.rs:18:8
+   |
+LL | #[repr(align())]
+   |        ^^^^^^^
+
 error[E0552]: invalid representation hint: `Rust` does not take a parenthesized argument list
   --> $DIR/malformed-repr-hints.rs:23:8
    |