diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index a353c79f12d45..837cb805700d2 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -887,7 +887,7 @@ fn validate_generic_param_order(dcx: DiagCtxtHandle<'_>, generics: &[GenericPara
 
 impl<'a> Visitor<'a> for AstValidator<'a> {
     fn visit_attribute(&mut self, attr: &Attribute) {
-        validate_attr::check_attr(&self.features, &self.session.psess, attr);
+        validate_attr::check_attr(&self.session.psess, attr);
     }
 
     fn visit_ty(&mut self, ty: &'a Ty) {
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 3ceb8e0711a21..214a37bca03e2 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -559,7 +559,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(mut_ref, "mutable by-reference bindings are experimental");
     gate_all!(precise_capturing, "precise captures on `impl Trait` are experimental");
     gate_all!(global_registration, "global registration is experimental");
-    gate_all!(unsafe_attributes, "`#[unsafe()]` markers for attributes are experimental");
     gate_all!(return_type_notation, "return type notation is experimental");
 
     if !visitor.features.never_patterns {
diff --git a/compiler/rustc_builtin_macros/src/cfg_accessible.rs b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
index 006b6aa823fbf..3d3bd3aea059c 100644
--- a/compiler/rustc_builtin_macros/src/cfg_accessible.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
@@ -47,7 +47,6 @@ impl MultiItemModifier for Expander {
     ) -> ExpandResult<Vec<Annotatable>, Annotatable> {
         let template = AttributeTemplate { list: Some("path"), ..Default::default() };
         validate_attr::check_builtin_meta_item(
-            &ecx.ecfg.features,
             &ecx.sess.psess,
             meta_item,
             ast::AttrStyle::Outer,
diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index 57bddf0ab60ad..e8704bc2f639d 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/compiler/rustc_builtin_macros/src/derive.rs
@@ -38,7 +38,6 @@ impl MultiItemModifier for Expander {
                 let template =
                     AttributeTemplate { list: Some("Trait1, Trait2, ..."), ..Default::default() };
                 validate_attr::check_builtin_meta_item(
-                    features,
                     &sess.psess,
                     meta_item,
                     ast::AttrStyle::Outer,
diff --git a/compiler/rustc_builtin_macros/src/util.rs b/compiler/rustc_builtin_macros/src/util.rs
index 73cc8ff547d51..0bcd5aef28bab 100644
--- a/compiler/rustc_builtin_macros/src/util.rs
+++ b/compiler/rustc_builtin_macros/src/util.rs
@@ -17,7 +17,6 @@ pub(crate) fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaI
     // All the built-in macro attributes are "words" at the moment.
     let template = AttributeTemplate { word: true, ..Default::default() };
     validate_attr::check_builtin_meta_item(
-        &ecx.ecfg.features,
         &ecx.sess.psess,
         meta_item,
         AttrStyle::Outer,
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index dd3f39eceadb6..1fd9f9e811671 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -1000,8 +1000,10 @@ impl<'ll> CodegenCx<'ll, '_> {
         ifn!("llvm.is.constant.i64", fn(t_i64) -> i1);
         ifn!("llvm.is.constant.i128", fn(t_i128) -> i1);
         ifn!("llvm.is.constant.isize", fn(t_isize) -> i1);
+        ifn!("llvm.is.constant.f16", fn(t_f16) -> i1);
         ifn!("llvm.is.constant.f32", fn(t_f32) -> i1);
         ifn!("llvm.is.constant.f64", fn(t_f64) -> i1);
+        ifn!("llvm.is.constant.f128", fn(t_f128) -> i1);
         ifn!("llvm.is.constant.ptr", fn(ptr) -> i1);
 
         ifn!("llvm.expect.i1", fn(i1, i1) -> i1);
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index f5558723d11bf..abfe38d4c0cc6 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -192,14 +192,22 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             }
             sym::is_val_statically_known => {
                 let intrinsic_type = args[0].layout.immediate_llvm_type(self.cx);
-                match self.type_kind(intrinsic_type) {
-                    TypeKind::Pointer | TypeKind::Integer | TypeKind::Float | TypeKind::Double => {
-                        self.call_intrinsic(
-                            &format!("llvm.is.constant.{:?}", intrinsic_type),
-                            &[args[0].immediate()],
-                        )
+                let kind = self.type_kind(intrinsic_type);
+                let intrinsic_name = match kind {
+                    TypeKind::Pointer | TypeKind::Integer => {
+                        Some(format!("llvm.is.constant.{intrinsic_type:?}"))
                     }
-                    _ => self.const_bool(false),
+                    // LLVM float types' intrinsic names differ from their type names.
+                    TypeKind::Half => Some(format!("llvm.is.constant.f16")),
+                    TypeKind::Float => Some(format!("llvm.is.constant.f32")),
+                    TypeKind::Double => Some(format!("llvm.is.constant.f64")),
+                    TypeKind::FP128 => Some(format!("llvm.is.constant.f128")),
+                    _ => None,
+                };
+                if let Some(intrinsic_name) = intrinsic_name {
+                    self.call_intrinsic(&intrinsic_name, &[args[0].immediate()])
+                } else {
+                    self.const_bool(false)
                 }
             }
             sym::unlikely => self
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index f6bf9f5e89f2f..b0d3fecbb479b 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -265,12 +265,7 @@ impl<'a> StripUnconfigured<'a> {
     /// is in the original source file. Gives a compiler error if the syntax of
     /// the attribute is incorrect.
     pub(crate) fn expand_cfg_attr(&self, cfg_attr: &Attribute, recursive: bool) -> Vec<Attribute> {
-        validate_attr::check_attribute_safety(
-            self.features.unwrap_or(&Features::default()),
-            &self.sess.psess,
-            AttributeSafety::Normal,
-            &cfg_attr,
-        );
+        validate_attr::check_attribute_safety(&self.sess.psess, AttributeSafety::Normal, &cfg_attr);
 
         let Some((cfg_predicate, expanded_attrs)) =
             rustc_parse::parse_cfg_attr(cfg_attr, &self.sess.psess)
@@ -395,11 +390,7 @@ impl<'a> StripUnconfigured<'a> {
             }
         };
 
-        validate_attr::deny_builtin_meta_unsafety(
-            self.features.unwrap_or(&Features::default()),
-            &self.sess.psess,
-            &meta_item,
-        );
+        validate_attr::deny_builtin_meta_unsafety(&self.sess.psess, &meta_item);
 
         (
             parse_cfg(&meta_item, self.sess).map_or(true, |meta_item| {
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 37679e17b90a8..cb6b13282a2ed 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -1882,7 +1882,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         let mut span: Option<Span> = None;
         while let Some(attr) = attrs.next() {
             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
-            validate_attr::check_attr(features, &self.cx.sess.psess, attr);
+            validate_attr::check_attr(&self.cx.sess.psess, attr);
 
             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
             span = Some(current_span);
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 03b40e28f8b4b..3d5ecbaae32a2 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -392,6 +392,8 @@ declare_features! (
     (accepted, universal_impl_trait, "1.26.0", Some(34511)),
     /// Allows arbitrary delimited token streams in non-macro attributes.
     (accepted, unrestricted_attribute_tokens, "1.34.0", Some(55208)),
+    /// Allows unsafe attributes.
+    (accepted, unsafe_attributes, "CURRENT_RUSTC_VERSION", Some(123757)),
     /// The `unsafe_op_in_unsafe_fn` lint (allowed by default): no longer treat an unsafe function as an unsafe block.
     (accepted, unsafe_block_in_unsafe_fn, "1.52.0", Some(71668)),
     /// Allows unsafe on extern declarations and safety qualifiers over internal items.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 24f691ea7fa20..459df9ea1b859 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -622,8 +622,6 @@ declare_features! (
     (unstable, type_changing_struct_update, "1.58.0", Some(86555)),
     /// Allows unnamed fields of struct and union type
     (incomplete, unnamed_fields, "1.74.0", Some(49804)),
-    /// Allows unsafe attributes.
-    (unstable, unsafe_attributes, "1.80.0", Some(123757)),
     /// Allows const generic parameters to be defined with types that
     /// are not `Sized`, e.g. `fn foo<const N: [u8]>() {`.
     (incomplete, unsized_const_params, "CURRENT_RUSTC_VERSION", Some(95174)),
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index c731b03a87590..56d77c9d1d04c 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -4971,7 +4971,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(unsafe_attributes)]
     /// #![warn(unsafe_attr_outside_unsafe)]
     ///
     /// #[no_mangle]
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index 3d06017fcf3c0..6391ff901cb74 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -4,7 +4,7 @@ use rustc_ast::token::{self, Delimiter};
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, PResult};
 use rustc_span::symbol::kw;
-use rustc_span::{sym, BytePos, Span};
+use rustc_span::{BytePos, Span};
 use thin_vec::ThinVec;
 use tracing::debug;
 
@@ -265,7 +265,6 @@ impl<'a> Parser<'a> {
             let is_unsafe = this.eat_keyword(kw::Unsafe);
             let unsafety = if is_unsafe {
                 let unsafe_span = this.prev_token.span;
-                this.psess.gated_spans.gate(sym::unsafe_attributes, unsafe_span);
                 this.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
                 ast::Safety::Unsafe(unsafe_span)
             } else {
@@ -406,7 +405,6 @@ impl<'a> Parser<'a> {
         };
         let unsafety = if is_unsafe {
             let unsafe_span = self.prev_token.span;
-            self.psess.gated_spans.gate(sym::unsafe_attributes, unsafe_span);
             self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
 
             ast::Safety::Unsafe(unsafe_span)
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index a64c00f3b6cbc..fce41bd90be7b 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -7,9 +7,7 @@ use rustc_ast::{
     NestedMetaItem, Safety,
 };
 use rustc_errors::{Applicability, FatalError, PResult};
-use rustc_feature::{
-    AttributeSafety, AttributeTemplate, BuiltinAttribute, Features, BUILTIN_ATTRIBUTE_MAP,
-};
+use rustc_feature::{AttributeSafety, AttributeTemplate, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
 use rustc_session::errors::report_lit_error;
 use rustc_session::lint::builtin::{ILL_FORMED_ATTRIBUTE_INPUT, UNSAFE_ATTR_OUTSIDE_UNSAFE};
 use rustc_session::lint::BuiltinLintDiag;
@@ -18,7 +16,7 @@ use rustc_span::{sym, BytePos, Span, Symbol};
 
 use crate::{errors, parse_in};
 
-pub fn check_attr(features: &Features, psess: &ParseSess, attr: &Attribute) {
+pub fn check_attr(psess: &ParseSess, attr: &Attribute) {
     if attr.is_doc_comment() {
         return;
     }
@@ -28,7 +26,7 @@ pub fn check_attr(features: &Features, psess: &ParseSess, attr: &Attribute) {
 
     // All non-builtin attributes are considered safe
     let safety = attr_info.map(|x| x.safety).unwrap_or(AttributeSafety::Normal);
-    check_attribute_safety(features, psess, safety, attr);
+    check_attribute_safety(psess, safety, attr);
 
     // Check input tokens for built-in and key-value attributes.
     match attr_info {
@@ -36,9 +34,9 @@ pub fn check_attr(features: &Features, psess: &ParseSess, attr: &Attribute) {
         Some(BuiltinAttribute { name, template, .. }) if *name != sym::rustc_dummy => {
             match parse_meta(psess, attr) {
                 // Don't check safety again, we just did that
-                Ok(meta) => check_builtin_meta_item(
-                    features, psess, &meta, attr.style, *name, *template, false,
-                ),
+                Ok(meta) => {
+                    check_builtin_meta_item(psess, &meta, attr.style, *name, *template, false)
+                }
                 Err(err) => {
                     err.emit();
                 }
@@ -157,16 +155,7 @@ fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaIte
     }
 }
 
-pub fn check_attribute_safety(
-    features: &Features,
-    psess: &ParseSess,
-    safety: AttributeSafety,
-    attr: &Attribute,
-) {
-    if !features.unsafe_attributes {
-        return;
-    }
-
+pub fn check_attribute_safety(psess: &ParseSess, safety: AttributeSafety, attr: &Attribute) {
     let attr_item = attr.get_normal_item();
 
     if safety == AttributeSafety::Unsafe {
@@ -215,21 +204,18 @@ pub fn check_attribute_safety(
 
 // Called by `check_builtin_meta_item` and code that manually denies
 // `unsafe(...)` in `cfg`
-pub fn deny_builtin_meta_unsafety(features: &Features, psess: &ParseSess, meta: &MetaItem) {
+pub fn deny_builtin_meta_unsafety(psess: &ParseSess, meta: &MetaItem) {
     // This only supports denying unsafety right now - making builtin attributes
     // support unsafety will requite us to thread the actual `Attribute` through
     // for the nice diagnostics.
-    if features.unsafe_attributes {
-        if let Safety::Unsafe(unsafe_span) = meta.unsafety {
-            psess
-                .dcx()
-                .emit_err(errors::InvalidAttrUnsafe { span: unsafe_span, name: meta.path.clone() });
-        }
+    if let Safety::Unsafe(unsafe_span) = meta.unsafety {
+        psess
+            .dcx()
+            .emit_err(errors::InvalidAttrUnsafe { span: unsafe_span, name: meta.path.clone() });
     }
 }
 
 pub fn check_builtin_meta_item(
-    features: &Features,
     psess: &ParseSess,
     meta: &MetaItem,
     style: ast::AttrStyle,
@@ -246,7 +232,7 @@ pub fn check_builtin_meta_item(
     }
 
     if deny_unsafety {
-        deny_builtin_meta_unsafety(features, psess, meta);
+        deny_builtin_meta_unsafety(psess, meta);
     }
 }
 
diff --git a/src/tools/rustfmt/tests/target/unsafe_attributes.rs b/src/tools/rustfmt/tests/target/unsafe_attributes.rs
index a05bedc751ae2..d79c56f21479f 100644
--- a/src/tools/rustfmt/tests/target/unsafe_attributes.rs
+++ b/src/tools/rustfmt/tests/target/unsafe_attributes.rs
@@ -1,4 +1,3 @@
-#![feature(unsafe_attributes)]
 // https://github.com/rust-lang/rust/issues/123757
 //
 #![simple_ident]
diff --git a/tests/codegen/is_val_statically_known.rs b/tests/codegen/is_val_statically_known.rs
index 6af4f353a481c..fe432d3bcc4de 100644
--- a/tests/codegen/is_val_statically_known.rs
+++ b/tests/codegen/is_val_statically_known.rs
@@ -1,6 +1,7 @@
 //@ compile-flags: --crate-type=lib -Zmerge-functions=disabled -O
 
 #![feature(core_intrinsics)]
+#![feature(f16, f128)]
 
 use std::intrinsics::is_val_statically_known;
 
@@ -49,7 +50,7 @@ pub fn _bool_false(b: bool) -> i32 {
 
 #[inline]
 pub fn _iref(a: &u8) -> i32 {
-    if unsafe { is_val_statically_known(a) } { 5 } else { 4 }
+    if is_val_statically_known(a) { 5 } else { 4 }
 }
 
 // CHECK-LABEL: @_iref_borrow(
@@ -68,7 +69,7 @@ pub fn _iref_arg(a: &u8) -> i32 {
 
 #[inline]
 pub fn _slice_ref(a: &[u8]) -> i32 {
-    if unsafe { is_val_statically_known(a) } { 7 } else { 6 }
+    if is_val_statically_known(a) { 7 } else { 6 }
 }
 
 // CHECK-LABEL: @_slice_ref_borrow(
@@ -84,3 +85,79 @@ pub fn _slice_ref_arg(a: &[u8]) -> i32 {
     // CHECK: ret i32 6
     _slice_ref(a)
 }
+
+#[inline]
+pub fn _f16(a: f16) -> i32 {
+    if is_val_statically_known(a) { 1 } else { 0 }
+}
+
+// CHECK-LABEL: @_f16_true(
+#[no_mangle]
+pub fn _f16_true() -> i32 {
+    // CHECK: ret i32 1
+    _f16(1.0)
+}
+
+// CHECK-LABEL: @_f16_false(
+#[no_mangle]
+pub fn _f16_false(a: f16) -> i32 {
+    // CHECK: ret i32 0
+    _f16(a)
+}
+
+#[inline]
+pub fn _f32(a: f32) -> i32 {
+    if is_val_statically_known(a) { 1 } else { 0 }
+}
+
+// CHECK-LABEL: @_f32_true(
+#[no_mangle]
+pub fn _f32_true() -> i32 {
+    // CHECK: ret i32 1
+    _f32(1.0)
+}
+
+// CHECK-LABEL: @_f32_false(
+#[no_mangle]
+pub fn _f32_false(a: f32) -> i32 {
+    // CHECK: ret i32 0
+    _f32(a)
+}
+
+#[inline]
+pub fn _f64(a: f64) -> i32 {
+    if is_val_statically_known(a) { 1 } else { 0 }
+}
+
+// CHECK-LABEL: @_f64_true(
+#[no_mangle]
+pub fn _f64_true() -> i32 {
+    // CHECK: ret i32 1
+    _f64(1.0)
+}
+
+// CHECK-LABEL: @_f64_false(
+#[no_mangle]
+pub fn _f64_false(a: f64) -> i32 {
+    // CHECK: ret i32 0
+    _f64(a)
+}
+
+#[inline]
+pub fn _f128(a: f128) -> i32 {
+    if is_val_statically_known(a) { 1 } else { 0 }
+}
+
+// CHECK-LABEL: @_f128_true(
+#[no_mangle]
+pub fn _f128_true() -> i32 {
+    // CHECK: ret i32 1
+    _f128(1.0)
+}
+
+// CHECK-LABEL: @_f128_false(
+#[no_mangle]
+pub fn _f128_false(a: f128) -> i32 {
+    // CHECK: ret i32 0
+    _f128(a)
+}
diff --git a/tests/debuginfo/drop-locations.rs b/tests/debuginfo/drop-locations.rs
index 0777313d19804..2db087dda7967 100644
--- a/tests/debuginfo/drop-locations.rs
+++ b/tests/debuginfo/drop-locations.rs
@@ -1,4 +1,3 @@
-//@ ignore-windows
 //@ ignore-android
 //@ min-lldb-version: 310
 //@ ignore-test: #128971
diff --git a/tests/debuginfo/embedded-visualizer.rs b/tests/debuginfo/embedded-visualizer.rs
index 69afd273f7735..959dbba7fd73c 100644
--- a/tests/debuginfo/embedded-visualizer.rs
+++ b/tests/debuginfo/embedded-visualizer.rs
@@ -1,7 +1,7 @@
 //@ compile-flags:-g
 //@ min-gdb-version: 8.1
 //@ ignore-lldb
-//@ ignore-windows-gnu // emit_debug_gdb_scripts is disabled on Windows
+//@ ignore-windows-gnu: #128981
 
 // === CDB TESTS ==================================================================================
 
diff --git a/tests/debuginfo/empty-string.rs b/tests/debuginfo/empty-string.rs
index 35b68ed91c0fc..eac3448bfd510 100644
--- a/tests/debuginfo/empty-string.rs
+++ b/tests/debuginfo/empty-string.rs
@@ -1,4 +1,4 @@
-//@ ignore-windows failing on win32 bot
+//@ ignore-windows-gnu: #128981
 //@ ignore-android: FIXME(#10381)
 //@ compile-flags:-g
 //@ min-gdb-version: 8.1
diff --git a/tests/debuginfo/issue-12886.rs b/tests/debuginfo/issue-12886.rs
index c6cf0dd4e05e3..48250e885374d 100644
--- a/tests/debuginfo/issue-12886.rs
+++ b/tests/debuginfo/issue-12886.rs
@@ -1,4 +1,3 @@
-//@ ignore-windows failing on 64-bit bots FIXME #17638
 //@ ignore-lldb
 //@ ignore-aarch64
 
@@ -6,7 +5,7 @@
 
 // gdb-command:run
 // gdb-command:next
-// gdb-check:[...]24[...]let s = Some(5).unwrap(); // #break
+// gdb-check:[...]23[...]let s = Some(5).unwrap(); // #break
 // gdb-command:continue
 
 #![feature(omit_gdb_pretty_printer_section)]
diff --git a/tests/debuginfo/macro-stepping.rs b/tests/debuginfo/macro-stepping.rs
index 3edac3c7832f9..35bb6de4fef38 100644
--- a/tests/debuginfo/macro-stepping.rs
+++ b/tests/debuginfo/macro-stepping.rs
@@ -1,4 +1,3 @@
-//@ ignore-windows
 //@ ignore-android
 //@ ignore-aarch64
 //@ min-lldb-version: 1800
diff --git a/tests/debuginfo/numeric-types.rs b/tests/debuginfo/numeric-types.rs
index 98bc31e88557a..6f45b69e5e34c 100644
--- a/tests/debuginfo/numeric-types.rs
+++ b/tests/debuginfo/numeric-types.rs
@@ -1,7 +1,7 @@
 //@ compile-flags:-g
 
 //@ min-gdb-version: 8.1
-//@ ignore-windows-gnu // emit_debug_gdb_scripts is disabled on Windows
+//@ ignore-windows-gnu: #128981
 
 // Tests the visualizations for `NonZero<T>`, `Wrapping<T>` and
 // `Atomic{Bool,I8,I16,I32,I64,Isize,U8,U16,U32,U64,Usize}` located in `libcore.natvis`.
diff --git a/tests/debuginfo/pretty-huge-vec.rs b/tests/debuginfo/pretty-huge-vec.rs
index dcf3521175d4c..b88e5db1acb8c 100644
--- a/tests/debuginfo/pretty-huge-vec.rs
+++ b/tests/debuginfo/pretty-huge-vec.rs
@@ -1,4 +1,4 @@
-//@ ignore-windows failing on win32 bot
+//@ ignore-windows-gnu: #128981
 //@ ignore-android: FIXME(#10381)
 //@ compile-flags:-g
 //@ min-gdb-version: 8.1
diff --git a/tests/debuginfo/pretty-slices.rs b/tests/debuginfo/pretty-slices.rs
index 9defa344be03e..44335f5c83b3f 100644
--- a/tests/debuginfo/pretty-slices.rs
+++ b/tests/debuginfo/pretty-slices.rs
@@ -1,5 +1,5 @@
 //@ ignore-android: FIXME(#10381)
-//@ ignore-windows
+//@ ignore-windows-gnu: #128981
 //@ compile-flags:-g
 
 // gdb-command: run
diff --git a/tests/debuginfo/pretty-std-collections.rs b/tests/debuginfo/pretty-std-collections.rs
index 3d5a30d19a9ce..3ec00886e2f40 100644
--- a/tests/debuginfo/pretty-std-collections.rs
+++ b/tests/debuginfo/pretty-std-collections.rs
@@ -1,4 +1,3 @@
-//@ ignore-windows failing on win32 bot
 //@ ignore-android: FIXME(#10381)
 //@ ignore-windows-gnu: #128981
 //@ compile-flags:-g
diff --git a/tests/debuginfo/pretty-uninitialized-vec.rs b/tests/debuginfo/pretty-uninitialized-vec.rs
index 5206ff23fd5ba..ddb751161d8ce 100644
--- a/tests/debuginfo/pretty-uninitialized-vec.rs
+++ b/tests/debuginfo/pretty-uninitialized-vec.rs
@@ -1,4 +1,4 @@
-//@ ignore-windows failing on win32 bot
+//@ ignore-windows-gnu: #128981
 //@ ignore-android: FIXME(#10381)
 //@ compile-flags:-g
 //@ min-gdb-version: 8.1
diff --git a/tests/debuginfo/thread-names.rs b/tests/debuginfo/thread-names.rs
index 6b3b0c7f4b231..265b9271cf306 100644
--- a/tests/debuginfo/thread-names.rs
+++ b/tests/debuginfo/thread-names.rs
@@ -4,7 +4,7 @@
 //@[macos] only-macos
 //@[win] only-windows
 //@ ignore-sgx
-//@ ignore-windows-gnu
+//@ ignore-windows-gnu: gdb on windows-gnu does not print thread names
 
 // === GDB TESTS ==================================================================================
 //
diff --git a/tests/run-make/dump-ice-to-disk/rmake.rs b/tests/run-make/dump-ice-to-disk/rmake.rs
index 48b4071e06541..08767246b90d0 100644
--- a/tests/run-make/dump-ice-to-disk/rmake.rs
+++ b/tests/run-make/dump-ice-to-disk/rmake.rs
@@ -14,11 +14,14 @@
 //!       that `RUSTC_ICE_PATH` takes precedence and no ICE dump is emitted under `METRICS_PATH`.
 //!
 //! See <https://github.com/rust-lang/rust/pull/108714>.
-
-//@ ignore-windows
-// FIXME(#128911): @jieyouxu: This test is sometimes for whatever forsaken reason flakey in
-// `i686-mingw`, and I cannot reproduce it locally. The error messages upon assertion failure in
-// this test is intentionally extremely verbose to aid debugging that issue.
+//!
+//! # Test history
+//!
+//! - The previous rmake.rs iteration of this test was flakey for unknown reason on `i686-mingw`
+//!   *specifically*, so assertion failures in this test was made extremely verbose to help
+//!   diagnose why the ICE messages was different *specifically* on `i686-mingw`.
+//! - An attempt is made to re-enable this test on `i686-mingw` (by removing `ignore-windows`). If
+//!   this test is still flakey, please restore the `ignore-windows` directive.
 
 use std::cell::OnceCell;
 use std::path::{Path, PathBuf};
diff --git a/tests/run-make/libtest-json/rmake.rs b/tests/run-make/libtest-json/rmake.rs
index acbd88dc46cb9..c31f4a79b641f 100644
--- a/tests/run-make/libtest-json/rmake.rs
+++ b/tests/run-make/libtest-json/rmake.rs
@@ -3,7 +3,7 @@
 //@ ignore-cross-compile
 //@ needs-unwind (test file contains #[should_panic] test)
 
-use run_make_support::{cmd, diff, python_command, rustc};
+use run_make_support::{cmd, diff, rustc, serde_json};
 
 fn main() {
     rustc().arg("--test").input("f.rs").run();
@@ -21,7 +21,18 @@ fn run_tests(extra_args: &[&str], expected_file: &str) {
         .run_fail();
     let test_stdout = &cmd_out.stdout_utf8();
 
-    python_command().arg("validate_json.py").stdin(test_stdout).run();
+    // Verify that the test process output is JSON Lines, i.e. each line is valid JSON.
+    for (line, n) in test_stdout.lines().zip(1..) {
+        if let Err(e) = serde_json::from_str::<serde_json::Value>(line) {
+            panic!(
+                "could not parse JSON on line {n}: {e}\n\
+                \n\
+                === STDOUT ===\n\
+                {test_stdout}\
+                =============="
+            );
+        }
+    }
 
     diff()
         .expected_file(expected_file)
diff --git a/tests/run-make/libtest-json/validate_json.py b/tests/run-make/libtest-json/validate_json.py
deleted file mode 100755
index 657f732f2bffd..0000000000000
--- a/tests/run-make/libtest-json/validate_json.py
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/usr/bin/env python
-
-import sys
-import json
-
-# Try to decode line in order to ensure it is a valid JSON document
-for line in sys.stdin:
-    json.loads(line)
diff --git a/tests/ui/attributes/unsafe/cfg-unsafe-attributes.rs b/tests/ui/attributes/unsafe/cfg-unsafe-attributes.rs
index ce365d1a8b1c8..6a9853b2f6fc6 100644
--- a/tests/ui/attributes/unsafe/cfg-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/cfg-unsafe-attributes.rs
@@ -1,5 +1,4 @@
 //@ build-pass
-#![feature(unsafe_attributes)]
 
 #[cfg_attr(all(), unsafe(no_mangle))]
 fn a() {}
diff --git a/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs b/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
index b8edb4aab907b..95fc19f506b24 100644
--- a/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
@@ -1,5 +1,3 @@
-#![feature(unsafe_attributes)]
-
 #[derive(unsafe(Debug))]
 //~^ ERROR: expected identifier, found keyword `unsafe`
 //~| ERROR: traits in `#[derive(...)]` don't accept arguments
diff --git a/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
index c40a5512fd5cd..4002c930b63e5 100644
--- a/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
@@ -1,5 +1,5 @@
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/derive-unsafe-attributes.rs:3:10
+  --> $DIR/derive-unsafe-attributes.rs:1:10
    |
 LL | #[derive(unsafe(Debug))]
    |          ^^^^^^ expected identifier, found keyword
@@ -10,13 +10,13 @@ LL | #[derive(r#unsafe(Debug))]
    |          ++
 
 error: traits in `#[derive(...)]` don't accept arguments
-  --> $DIR/derive-unsafe-attributes.rs:3:16
+  --> $DIR/derive-unsafe-attributes.rs:1:16
    |
 LL | #[derive(unsafe(Debug))]
    |                ^^^^^^^ help: remove the arguments
 
 error: `derive` is not an unsafe attribute
-  --> $DIR/derive-unsafe-attributes.rs:12:3
+  --> $DIR/derive-unsafe-attributes.rs:10:3
    |
 LL | #[unsafe(derive(Debug))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -24,7 +24,7 @@ LL | #[unsafe(derive(Debug))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/derive-unsafe-attributes.rs:3:10
+  --> $DIR/derive-unsafe-attributes.rs:1:10
    |
 LL | #[derive(unsafe(Debug))]
    |          ^^^^^^ expected identifier, found keyword
@@ -36,7 +36,7 @@ LL | #[derive(r#unsafe(Debug))]
    |          ++
 
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/derive-unsafe-attributes.rs:3:10
+  --> $DIR/derive-unsafe-attributes.rs:1:10
    |
 LL | #[derive(unsafe(Debug))]
    |          ^^^^^^ expected identifier, found keyword
@@ -48,13 +48,13 @@ LL | #[derive(r#unsafe(Debug))]
    |          ++
 
 error: cannot find derive macro `r#unsafe` in this scope
-  --> $DIR/derive-unsafe-attributes.rs:3:10
+  --> $DIR/derive-unsafe-attributes.rs:1:10
    |
 LL | #[derive(unsafe(Debug))]
    |          ^^^^^^
 
 error: cannot find derive macro `r#unsafe` in this scope
-  --> $DIR/derive-unsafe-attributes.rs:3:10
+  --> $DIR/derive-unsafe-attributes.rs:1:10
    |
 LL | #[derive(unsafe(Debug))]
    |          ^^^^^^
diff --git a/tests/ui/attributes/unsafe/double-unsafe-attributes.rs b/tests/ui/attributes/unsafe/double-unsafe-attributes.rs
index a6c0ea578f25a..894d1327da799 100644
--- a/tests/ui/attributes/unsafe/double-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/double-unsafe-attributes.rs
@@ -1,5 +1,3 @@
-#![feature(unsafe_attributes)]
-
 #[unsafe(unsafe(no_mangle))]
 //~^ ERROR expected identifier, found keyword `unsafe`
 //~| ERROR cannot find attribute `r#unsafe` in this scope
diff --git a/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
index 950b2636993c1..0825cf794083d 100644
--- a/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
@@ -1,5 +1,5 @@
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/double-unsafe-attributes.rs:3:10
+  --> $DIR/double-unsafe-attributes.rs:1:10
    |
 LL | #[unsafe(unsafe(no_mangle))]
    |          ^^^^^^ expected identifier, found keyword
@@ -10,7 +10,7 @@ LL | #[unsafe(r#unsafe(no_mangle))]
    |          ++
 
 error: `r#unsafe` is not an unsafe attribute
-  --> $DIR/double-unsafe-attributes.rs:3:3
+  --> $DIR/double-unsafe-attributes.rs:1:3
    |
 LL | #[unsafe(unsafe(no_mangle))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -18,7 +18,7 @@ LL | #[unsafe(unsafe(no_mangle))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: cannot find attribute `r#unsafe` in this scope
-  --> $DIR/double-unsafe-attributes.rs:3:10
+  --> $DIR/double-unsafe-attributes.rs:1:10
    |
 LL | #[unsafe(unsafe(no_mangle))]
    |          ^^^^^^
diff --git a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.rs b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.rs
index 0181add843bcd..b561550c19843 100644
--- a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.rs
@@ -1,6 +1,5 @@
 //@ edition: 2024
 //@ compile-flags: -Zunstable-options
-#![feature(unsafe_attributes)]
 
 #[unsafe(cfg(any()))] //~ ERROR: is not an unsafe attribute
 fn a() {}
diff --git a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
index f39074b613d40..9fb7f062b912b 100644
--- a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
@@ -1,5 +1,5 @@
 error: `cfg` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:5:3
+  --> $DIR/extraneous-unsafe-attributes.rs:4:3
    |
 LL | #[unsafe(cfg(any()))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -7,7 +7,7 @@ LL | #[unsafe(cfg(any()))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `cfg_attr` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:8:3
+  --> $DIR/extraneous-unsafe-attributes.rs:7:3
    |
 LL | #[unsafe(cfg_attr(any(), allow(dead_code)))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -15,7 +15,7 @@ LL | #[unsafe(cfg_attr(any(), allow(dead_code)))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `test` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:11:3
+  --> $DIR/extraneous-unsafe-attributes.rs:10:3
    |
 LL | #[unsafe(test)]
    |   ^^^^^^ this is not an unsafe attribute
@@ -23,7 +23,7 @@ LL | #[unsafe(test)]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `ignore` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:14:3
+  --> $DIR/extraneous-unsafe-attributes.rs:13:3
    |
 LL | #[unsafe(ignore = "test")]
    |   ^^^^^^ this is not an unsafe attribute
@@ -31,7 +31,7 @@ LL | #[unsafe(ignore = "test")]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `should_panic` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:17:3
+  --> $DIR/extraneous-unsafe-attributes.rs:16:3
    |
 LL | #[unsafe(should_panic(expected = "test"))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -39,7 +39,7 @@ LL | #[unsafe(should_panic(expected = "test"))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `macro_use` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:20:3
+  --> $DIR/extraneous-unsafe-attributes.rs:19:3
    |
 LL | #[unsafe(macro_use)]
    |   ^^^^^^ this is not an unsafe attribute
@@ -47,7 +47,7 @@ LL | #[unsafe(macro_use)]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `macro_export` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:22:7
+  --> $DIR/extraneous-unsafe-attributes.rs:21:7
    |
 LL |     #[unsafe(macro_export)]
    |       ^^^^^^ this is not an unsafe attribute
@@ -55,7 +55,7 @@ LL |     #[unsafe(macro_export)]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `used` is not an unsafe attribute
-  --> $DIR/extraneous-unsafe-attributes.rs:28:3
+  --> $DIR/extraneous-unsafe-attributes.rs:27:3
    |
 LL | #[unsafe(used)]
    |   ^^^^^^ this is not an unsafe attribute
diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs b/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
index f29a5b3252b0a..eaf8706369a5a 100644
--- a/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
@@ -1,5 +1,3 @@
-#![feature(unsafe_attributes)]
-
 #[unsafe(proc_macro)]
 //~^ ERROR: is not an unsafe attribute
 //~| ERROR attribute is only usable with crates of the `proc-macro` crate type
diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
index 79d34d458bd6c..9c5751c82e4c4 100644
--- a/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
@@ -1,11 +1,11 @@
 error[E0452]: malformed lint attribute input
-  --> $DIR/proc-unsafe-attributes.rs:28:16
+  --> $DIR/proc-unsafe-attributes.rs:26:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |                ^^^^^^^^^^^^^^^^^ bad attribute argument
 
 error[E0452]: malformed lint attribute input
-  --> $DIR/proc-unsafe-attributes.rs:28:16
+  --> $DIR/proc-unsafe-attributes.rs:26:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |                ^^^^^^^^^^^^^^^^^ bad attribute argument
@@ -13,7 +13,7 @@ LL | #[unsafe(allow(unsafe(dead_code)))]
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `proc_macro` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:3:3
+  --> $DIR/proc-unsafe-attributes.rs:1:3
    |
 LL | #[unsafe(proc_macro)]
    |   ^^^^^^ this is not an unsafe attribute
@@ -21,7 +21,7 @@ LL | #[unsafe(proc_macro)]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `proc_macro_derive` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:9:3
+  --> $DIR/proc-unsafe-attributes.rs:7:3
    |
 LL | #[unsafe(proc_macro_derive(Foo))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -29,7 +29,7 @@ LL | #[unsafe(proc_macro_derive(Foo))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/proc-unsafe-attributes.rs:14:21
+  --> $DIR/proc-unsafe-attributes.rs:12:21
    |
 LL | #[proc_macro_derive(unsafe(Foo))]
    |                     ^^^^^^ expected identifier, found keyword
@@ -40,7 +40,7 @@ LL | #[proc_macro_derive(r#unsafe(Foo))]
    |                     ++
 
 error: `proc_macro_attribute` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:19:3
+  --> $DIR/proc-unsafe-attributes.rs:17:3
    |
 LL | #[unsafe(proc_macro_attribute)]
    |   ^^^^^^ this is not an unsafe attribute
@@ -48,7 +48,7 @@ LL | #[unsafe(proc_macro_attribute)]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `allow` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:24:3
+  --> $DIR/proc-unsafe-attributes.rs:22:3
    |
 LL | #[unsafe(allow(dead_code))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -56,7 +56,7 @@ LL | #[unsafe(allow(dead_code))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: `allow` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:28:3
+  --> $DIR/proc-unsafe-attributes.rs:26:3
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |   ^^^^^^ this is not an unsafe attribute
@@ -64,7 +64,7 @@ LL | #[unsafe(allow(unsafe(dead_code)))]
    = note: extraneous unsafe is not allowed in attributes
 
 error: expected identifier, found keyword `unsafe`
-  --> $DIR/proc-unsafe-attributes.rs:28:16
+  --> $DIR/proc-unsafe-attributes.rs:26:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |                ^^^^^^ expected identifier, found keyword
@@ -75,31 +75,31 @@ LL | #[unsafe(allow(r#unsafe(dead_code)))]
    |                ++
 
 error: the `#[proc_macro]` attribute is only usable with crates of the `proc-macro` crate type
-  --> $DIR/proc-unsafe-attributes.rs:3:1
+  --> $DIR/proc-unsafe-attributes.rs:1:1
    |
 LL | #[unsafe(proc_macro)]
    | ^^^^^^^^^^^^^^^^^^^^^
 
 error: the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type
-  --> $DIR/proc-unsafe-attributes.rs:9:1
+  --> $DIR/proc-unsafe-attributes.rs:7:1
    |
 LL | #[unsafe(proc_macro_derive(Foo))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type
-  --> $DIR/proc-unsafe-attributes.rs:14:1
+  --> $DIR/proc-unsafe-attributes.rs:12:1
    |
 LL | #[proc_macro_derive(unsafe(Foo))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: the `#[proc_macro_attribute]` attribute is only usable with crates of the `proc-macro` crate type
-  --> $DIR/proc-unsafe-attributes.rs:19:1
+  --> $DIR/proc-unsafe-attributes.rs:17:1
    |
 LL | #[unsafe(proc_macro_attribute)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0452]: malformed lint attribute input
-  --> $DIR/proc-unsafe-attributes.rs:28:16
+  --> $DIR/proc-unsafe-attributes.rs:26:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |                ^^^^^^^^^^^^^^^^^ bad attribute argument
@@ -107,7 +107,7 @@ LL | #[unsafe(allow(unsafe(dead_code)))]
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0452]: malformed lint attribute input
-  --> $DIR/proc-unsafe-attributes.rs:28:16
+  --> $DIR/proc-unsafe-attributes.rs:26:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
    |                ^^^^^^^^^^^^^^^^^ bad attribute argument
diff --git a/tests/ui/attributes/unsafe/unsafe-attributes.rs b/tests/ui/attributes/unsafe/unsafe-attributes.rs
index 33a412add500c..5c57767b3b964 100644
--- a/tests/ui/attributes/unsafe/unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/unsafe-attributes.rs
@@ -1,5 +1,4 @@
 //@ build-pass
-#![feature(unsafe_attributes)]
 
 #[unsafe(no_mangle)]
 fn a() {}
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute.rs b/tests/ui/attributes/unsafe/unsafe-safe-attribute.rs
index 67db36afd2e69..5af03a2b8d137 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute.rs
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute.rs
@@ -1,5 +1,3 @@
-#![feature(unsafe_attributes)]
-
 #[unsafe(repr(C))] //~ ERROR: is not an unsafe attribute
 struct Foo {}
 
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr b/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
index 584b0ea797d0a..55172c91aaeef 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
@@ -1,5 +1,5 @@
 error: `repr` is not an unsafe attribute
-  --> $DIR/unsafe-safe-attribute.rs:3:3
+  --> $DIR/unsafe-safe-attribute.rs:1:3
    |
 LL | #[unsafe(repr(C))]
    |   ^^^^^^ this is not an unsafe attribute
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.rs b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.rs
index ff2eb61b40538..0f241cc439f34 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.rs
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.rs
@@ -1,5 +1,3 @@
-#![feature(unsafe_attributes)]
-
 #[unsafe(diagnostic::on_unimplemented( //~ ERROR: is not an unsafe attribute
     message = "testing",
 ))]
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
index 26b5e4e37b931..3bc291db5acf8 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
@@ -1,5 +1,5 @@
 error: `diagnostic::on_unimplemented` is not an unsafe attribute
-  --> $DIR/unsafe-safe-attribute_diagnostic.rs:3:3
+  --> $DIR/unsafe-safe-attribute_diagnostic.rs:1:3
    |
 LL | #[unsafe(diagnostic::on_unimplemented(
    |   ^^^^^^ this is not an unsafe attribute
diff --git a/tests/ui/consts/const-float-bits-conv.rs b/tests/ui/consts/const-float-bits-conv.rs
index 45e8ea570ed73..2c4df96562a9d 100644
--- a/tests/ui/consts/const-float-bits-conv.rs
+++ b/tests/ui/consts/const-float-bits-conv.rs
@@ -3,8 +3,9 @@
 
 #![feature(const_float_bits_conv)]
 #![feature(const_float_classify)]
+#![feature(f16)]
+#![feature(f128)]
 #![allow(unused_macro_rules)]
-
 // Don't promote
 const fn nop<T>(x: T) -> T { x }
 
@@ -28,6 +29,36 @@ fn has_broken_floats() -> bool {
     std::env::var("TARGET").is_ok_and(|v| v.contains("i586"))
 }
 
+fn f16(){
+    const_assert!((1f16).to_bits(), 0x3c00);
+    const_assert!(u16::from_be_bytes(1f16.to_be_bytes()), 0x3c00);
+    const_assert!((12.5f16).to_bits(), 0x4a40);
+    const_assert!(u16::from_le_bytes(12.5f16.to_le_bytes()), 0x4a40);
+    const_assert!((1337f16).to_bits(), 0x6539);
+    const_assert!(u16::from_ne_bytes(1337f16.to_ne_bytes()), 0x6539);
+    const_assert!((-14.25f16).to_bits(), 0xcb20);
+    const_assert!(f16::from_bits(0x3c00), 1.0);
+    const_assert!(f16::from_be_bytes(0x3c00u16.to_be_bytes()), 1.0);
+    const_assert!(f16::from_bits(0x4a40), 12.5);
+    const_assert!(f16::from_le_bytes(0x4a40u16.to_le_bytes()), 12.5);
+    const_assert!(f16::from_bits(0x5be0), 252.0);
+    const_assert!(f16::from_ne_bytes(0x5be0u16.to_ne_bytes()), 252.0);
+    const_assert!(f16::from_bits(0xcb20), -14.25);
+
+    // Check that NaNs roundtrip their bits regardless of signalingness
+    // 0xA is 0b1010; 0x5 is 0b0101 -- so these two together clobbers all the mantissa bits
+    // NOTE: These names assume `f{BITS}::NAN` is a quiet NAN and IEEE754-2008's NaN rules apply!
+    const QUIET_NAN: u16 = f16::NAN.to_bits() ^ 0x0155;
+    const SIGNALING_NAN: u16 = f16::NAN.to_bits() ^ 0x02AA;
+
+    const_assert!(f16::from_bits(QUIET_NAN).is_nan());
+    const_assert!(f16::from_bits(SIGNALING_NAN).is_nan());
+    const_assert!(f16::from_bits(QUIET_NAN).to_bits(), QUIET_NAN);
+    if !has_broken_floats() {
+        const_assert!(f16::from_bits(SIGNALING_NAN).to_bits(), SIGNALING_NAN);
+    }
+}
+
 fn f32() {
     const_assert!((1f32).to_bits(), 0x3f800000);
     const_assert!(u32::from_be_bytes(1f32.to_be_bytes()), 0x3f800000);
@@ -88,7 +119,39 @@ fn f64() {
     }
 }
 
+fn f128() {
+    const_assert!((1f128).to_bits(), 0x3fff0000000000000000000000000000);
+    const_assert!(u128::from_be_bytes(1f128.to_be_bytes()), 0x3fff0000000000000000000000000000);
+    const_assert!((12.5f128).to_bits(), 0x40029000000000000000000000000000);
+    const_assert!(u128::from_le_bytes(12.5f128.to_le_bytes()), 0x40029000000000000000000000000000);
+    const_assert!((1337f128).to_bits(), 0x40094e40000000000000000000000000);
+    const_assert!(u128::from_ne_bytes(1337f128.to_ne_bytes()), 0x40094e40000000000000000000000000);
+    const_assert!((-14.25f128).to_bits(), 0xc002c800000000000000000000000000);
+    const_assert!(f128::from_bits(0x3fff0000000000000000000000000000), 1.0);
+    const_assert!(f128::from_be_bytes(0x3fff0000000000000000000000000000u128.to_be_bytes()), 1.0);
+    const_assert!(f128::from_bits(0x40029000000000000000000000000000), 12.5);
+    const_assert!(f128::from_le_bytes(0x40029000000000000000000000000000u128.to_le_bytes()), 12.5);
+    const_assert!(f128::from_bits(0x40094e40000000000000000000000000), 1337.0);
+    assert_eq!(f128::from_ne_bytes(0x40094e40000000000000000000000000u128.to_ne_bytes()), 1337.0);
+    const_assert!(f128::from_bits(0xc002c800000000000000000000000000), -14.25);
+
+    // Check that NaNs roundtrip their bits regardless of signalingness
+    // 0xA is 0b1010; 0x5 is 0b0101 -- so these two together clobbers all the mantissa bits
+    // NOTE: These names assume `f{BITS}::NAN` is a quiet NAN and IEEE754-2008's NaN rules apply!
+    const QUIET_NAN: u128 = f128::NAN.to_bits() | 0x0000_AAAA_AAAA_AAAA_AAAA_AAAA_AAAA_AAAA;
+    const SIGNALING_NAN: u128 = f128::NAN.to_bits() ^ 0x0000_5555_5555_5555_5555_5555_5555_5555;
+
+    const_assert!(f128::from_bits(QUIET_NAN).is_nan());
+    const_assert!(f128::from_bits(SIGNALING_NAN).is_nan());
+    const_assert!(f128::from_bits(QUIET_NAN).to_bits(), QUIET_NAN);
+    if !has_broken_floats() {
+        const_assert!(f128::from_bits(SIGNALING_NAN).to_bits(), SIGNALING_NAN);
+    }
+}
+
 fn main() {
+    f16();
     f32();
     f64();
+    f128();
 }
diff --git a/tests/ui/feature-gates/feature-gate-unsafe-attributes.rs b/tests/ui/feature-gates/feature-gate-unsafe-attributes.rs
deleted file mode 100644
index 9eba415dda0e5..0000000000000
--- a/tests/ui/feature-gates/feature-gate-unsafe-attributes.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-#[unsafe(no_mangle)] //~ ERROR [E0658]
-extern "C" fn foo() {
-
-}
-
-fn main() {
-    foo();
-}
diff --git a/tests/ui/feature-gates/feature-gate-unsafe-attributes.stderr b/tests/ui/feature-gates/feature-gate-unsafe-attributes.stderr
deleted file mode 100644
index dfcea756b02b6..0000000000000
--- a/tests/ui/feature-gates/feature-gate-unsafe-attributes.stderr
+++ /dev/null
@@ -1,13 +0,0 @@
-error[E0658]: `#[unsafe()]` markers for attributes are experimental
-  --> $DIR/feature-gate-unsafe-attributes.rs:1:3
-   |
-LL | #[unsafe(no_mangle)]
-   |   ^^^^^^
-   |
-   = note: see issue #123757 <https://github.com/rust-lang/rust/issues/123757> for more information
-   = help: add `#![feature(unsafe_attributes)]` 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`.
diff --git a/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.rs b/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.rs
index c6f9115cde750..f3b8645abaf89 100644
--- a/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.rs
+++ b/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.rs
@@ -1,5 +1,4 @@
 #![deny(rust_2024_compatibility)]
-#![feature(unsafe_attributes)]
 
 #[no_mangle]
 //~^ ERROR: unsafe attribute used without unsafe
diff --git a/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.stderr b/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.stderr
index f0689d9883c9e..4629a154ac3ce 100644
--- a/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.stderr
+++ b/tests/ui/rust-2024/unsafe-attributes/in_2024_compatibility.stderr
@@ -1,5 +1,5 @@
 error: unsafe attribute used without unsafe
-  --> $DIR/in_2024_compatibility.rs:4:3
+  --> $DIR/in_2024_compatibility.rs:3:3
    |
 LL | #[no_mangle]
    |   ^^^^^^^^^ usage of unsafe attribute
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attribute-marked.rs b/tests/ui/rust-2024/unsafe-attributes/unsafe-attribute-marked.rs
index 279ced2525a23..7c919fed976f5 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attribute-marked.rs
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attribute-marked.rs
@@ -4,7 +4,6 @@
 //@[edition2024] compile-flags: -Zunstable-options
 //@ check-pass
 
-#![feature(unsafe_attributes)]
 
 #[unsafe(no_mangle)]
 extern "C" fn foo() {}
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.fixed b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.fixed
index 6ebdff0334c8b..586881d180767 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.fixed
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.fixed
@@ -1,5 +1,4 @@
 //@ run-rustfix
-#![feature(unsafe_attributes)]
 #![deny(unsafe_attr_outside_unsafe)]
 
 macro_rules! tt {
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.rs b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.rs
index c78ff45ea4cdf..03e122c7d57e7 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.rs
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.rs
@@ -1,5 +1,4 @@
 //@ run-rustfix
-#![feature(unsafe_attributes)]
 #![deny(unsafe_attr_outside_unsafe)]
 
 macro_rules! tt {
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.stderr b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.stderr
index c95984f58ecf7..64debc58905c3 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.stderr
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-fix.stderr
@@ -1,5 +1,5 @@
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:44:6
+  --> $DIR/unsafe-attributes-fix.rs:43:6
    |
 LL | tt!([no_mangle]);
    |      ^^^^^^^^^ usage of unsafe attribute
@@ -7,7 +7,7 @@ LL | tt!([no_mangle]);
    = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2024!
    = note: for more information, see issue #123757 <https://github.com/rust-lang/rust/issues/123757>
 note: the lint level is defined here
-  --> $DIR/unsafe-attributes-fix.rs:3:9
+  --> $DIR/unsafe-attributes-fix.rs:2:9
    |
 LL | #![deny(unsafe_attr_outside_unsafe)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -17,7 +17,7 @@ LL | tt!([unsafe(no_mangle)]);
    |      +++++++         +
 
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:14:11
+  --> $DIR/unsafe-attributes-fix.rs:13:11
    |
 LL |         #[$e]
    |           ^^ usage of unsafe attribute
@@ -34,7 +34,7 @@ LL |         #[unsafe($e)]
    |           +++++++  +
 
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:48:7
+  --> $DIR/unsafe-attributes-fix.rs:47:7
    |
 LL | meta!(no_mangle);
    |       ^^^^^^^^^ usage of unsafe attribute
@@ -47,7 +47,7 @@ LL | meta!(unsafe(no_mangle));
    |       +++++++         +
 
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:51:8
+  --> $DIR/unsafe-attributes-fix.rs:50:8
    |
 LL | meta2!(export_name = "baw");
    |        ^^^^^^^^^^^ usage of unsafe attribute
@@ -60,7 +60,7 @@ LL | meta2!(unsafe(export_name = "baw"));
    |        +++++++                   +
 
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:23:11
+  --> $DIR/unsafe-attributes-fix.rs:22:11
    |
 LL |         #[$e = $l]
    |           ^^ usage of unsafe attribute
@@ -77,7 +77,7 @@ LL |         #[unsafe($e = $l)]
    |           +++++++       +
 
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes-fix.rs:56:3
+  --> $DIR/unsafe-attributes-fix.rs:55:3
    |
 LL | #[no_mangle]
    |   ^^^^^^^^^ usage of unsafe attribute
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.edition2024.stderr b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.edition2024.stderr
index 35475d6671626..fb697e14ef1c7 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.edition2024.stderr
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.edition2024.stderr
@@ -1,5 +1,5 @@
 error: unsafe attribute used without unsafe
-  --> $DIR/unsafe-attributes.rs:9:3
+  --> $DIR/unsafe-attributes.rs:8:3
    |
 LL | #[no_mangle]
    |   ^^^^^^^^^ usage of unsafe attribute
diff --git a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.rs b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.rs
index 3a6af9dfb2b0f..f6f2994bb6def 100644
--- a/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.rs
+++ b/tests/ui/rust-2024/unsafe-attributes/unsafe-attributes.rs
@@ -4,7 +4,6 @@
 //@[edition2024] edition:2024
 //@[edition2024] compile-flags: -Zunstable-options
 
-#![feature(unsafe_attributes)]
 
 #[no_mangle] //[edition2024]~ ERROR: unsafe attribute used without unsafe
 extern "C" fn foo() {}