diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 7c76392858cd5..08b2115b79406 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -80,6 +80,8 @@ declare_features! (
     (accepted, braced_empty_structs, "1.8.0", Some(29720)),
     /// Allows `c"foo"` literals.
     (accepted, c_str_literals, "1.77.0", Some(105723)),
+    /// Allows `extern "C-unwind" fn` to enable unwinding across ABI boundaries and treat `extern "C" fn` as nounwind.
+    (accepted, c_unwind, "CURRENT_RUSTC_VERSION", Some(74990)),
     /// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
     (accepted, cfg_attr_multi, "1.33.0", Some(54881)),
     /// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 8add2b9276142..5252f91ccf37b 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -363,8 +363,6 @@ declare_features! (
     (unstable, async_for_loop, "1.77.0", Some(118898)),
     /// Allows builtin # foo() syntax
     (unstable, builtin_syntax, "1.71.0", Some(110680)),
-    /// Treat `extern "C"` function as nounwind.
-    (unstable, c_unwind, "1.52.0", Some(74990)),
     /// Allows using C-variadics.
     (unstable, c_variadic, "1.34.0", Some(44930)),
     /// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour.
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 142872009bf21..596f423fc92bf 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1181,37 +1181,6 @@ pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: SpecAbi) ->
     // ABIs have such an option. Otherwise the only other thing here is Rust
     // itself, and those ABIs are determined by the panic strategy configured
     // for this compilation.
-    //
-    // Unfortunately at this time there's also another caveat. Rust [RFC
-    // 2945][rfc] has been accepted and is in the process of being implemented
-    // and stabilized. In this interim state we need to deal with historical
-    // rustc behavior as well as plan for future rustc behavior.
-    //
-    // Historically functions declared with `extern "C"` were marked at the
-    // codegen layer as `nounwind`. This happened regardless of `panic=unwind`
-    // or not. This is UB for functions in `panic=unwind` mode that then
-    // actually panic and unwind. Note that this behavior is true for both
-    // externally declared functions as well as Rust-defined function.
-    //
-    // To fix this UB rustc would like to change in the future to catch unwinds
-    // from function calls that may unwind within a Rust-defined `extern "C"`
-    // function and forcibly abort the process, thereby respecting the
-    // `nounwind` attribute emitted for `extern "C"`. This behavior change isn't
-    // ready to roll out, so determining whether or not the `C` family of ABIs
-    // unwinds is conditional not only on their definition but also whether the
-    // `#![feature(c_unwind)]` feature gate is active.
-    //
-    // Note that this means that unlike historical compilers rustc now, by
-    // default, unconditionally thinks that the `C` ABI may unwind. This will
-    // prevent some optimization opportunities, however, so we try to scope this
-    // change and only assume that `C` unwinds with `panic=unwind` (as opposed
-    // to `panic=abort`).
-    //
-    // Eventually the check against `c_unwind` here will ideally get removed and
-    // this'll be a little cleaner as it'll be a straightforward check of the
-    // ABI.
-    //
-    // [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
     use SpecAbi::*;
     match abi {
         C { unwind }
@@ -1223,10 +1192,7 @@ pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: SpecAbi) ->
         | Thiscall { unwind }
         | Aapcs { unwind }
         | Win64 { unwind }
-        | SysV64 { unwind } => {
-            unwind
-                || (!tcx.features().c_unwind && tcx.sess.panic_strategy() == PanicStrategy::Unwind)
-        }
+        | SysV64 { unwind } => unwind,
         PtxKernel
         | Msp430Interrupt
         | X86Interrupt
diff --git a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
index 5e3cd85367508..0cb304da80a10 100644
--- a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
+++ b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
@@ -11,38 +11,6 @@ use rustc_target::spec::PanicStrategy;
 
 use crate::errors;
 
-/// Some of the functions declared as "may unwind" by `fn_can_unwind` can't actually unwind. In
-/// particular, `extern "C"` is still considered as can-unwind on stable, but we need to consider
-/// it cannot-unwind here. So below we check `fn_can_unwind() && abi_can_unwind()` before concluding
-/// that a function call can unwind.
-fn abi_can_unwind(abi: Abi) -> bool {
-    use Abi::*;
-    match abi {
-        C { unwind }
-        | System { unwind }
-        | Cdecl { unwind }
-        | Stdcall { unwind }
-        | Fastcall { unwind }
-        | Vectorcall { unwind }
-        | Thiscall { unwind }
-        | Aapcs { unwind }
-        | Win64 { unwind }
-        | SysV64 { unwind } => unwind,
-        PtxKernel
-        | Msp430Interrupt
-        | X86Interrupt
-        | EfiApi
-        | AvrInterrupt
-        | AvrNonBlockingInterrupt
-        | RiscvInterruptM
-        | RiscvInterruptS
-        | CCmseNonSecureCall
-        | Wasm
-        | Unadjusted => false,
-        RustIntrinsic | Rust | RustCall | RustCold => unreachable!(), // these ABIs are already skipped earlier
-    }
-}
-
 // Check if the body of this def_id can possibly leak a foreign unwind into Rust code.
 fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
     debug!("has_ffi_unwind_calls({local_def_id:?})");
@@ -103,7 +71,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
             _ => bug!("invalid callee of type {:?}", ty),
         };
 
-        if layout::fn_can_unwind(tcx, fn_def_id, sig.abi()) && abi_can_unwind(sig.abi()) {
+        if layout::fn_can_unwind(tcx, fn_def_id, sig.abi()) {
             // We have detected a call that can possibly leak foreign unwind.
             //
             // Because the function body itself can unwind, we are not aborting this function call
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 4ac0c9b15be7a..ab18814bb8176 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -166,13 +166,13 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![cfg_attr(bootstrap, feature(exclusive_range_pattern))]
 #![cfg_attr(not(test), feature(coroutine_trait))]
 #![cfg_attr(test, feature(panic_update_hook))]
 #![cfg_attr(test, feature(test))]
 #![feature(allocator_internals)]
 #![feature(allow_internal_unstable)]
-#![feature(c_unwind)]
 #![feature(cfg_sanitize)]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 89642d6226a24..bd467437281c1 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -199,13 +199,13 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
 #![feature(asm_const)]
 #![feature(auto_traits)]
-#![feature(c_unwind)]
 #![feature(cfg_sanitize)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_has_atomic_equal_alignment)]
diff --git a/library/panic_abort/src/lib.rs b/library/panic_abort/src/lib.rs
index 353de8c5c5743..14ba4af2bb575 100644
--- a/library/panic_abort/src/lib.rs
+++ b/library/panic_abort/src/lib.rs
@@ -14,7 +14,7 @@
 #![feature(std_internals)]
 #![feature(staged_api)]
 #![feature(rustc_attrs)]
-#![feature(c_unwind)]
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![allow(internal_features)]
 
 #[cfg(target_os = "android")]
diff --git a/library/panic_unwind/src/lib.rs b/library/panic_unwind/src/lib.rs
index b0245de501e7e..4dc3612060848 100644
--- a/library/panic_unwind/src/lib.rs
+++ b/library/panic_unwind/src/lib.rs
@@ -24,7 +24,7 @@
 #![feature(rustc_attrs)]
 #![panic_runtime]
 #![feature(panic_runtime)]
-#![feature(c_unwind)]
+#![cfg_attr(bootstrap, feature(c_unwind))]
 // `real_imp` is unused with Miri, so silence warnings.
 #![cfg_attr(miri, allow(dead_code))]
 #![allow(internal_features)]
diff --git a/library/proc_macro/src/bridge/buffer.rs b/library/proc_macro/src/bridge/buffer.rs
index 48030f8d82dca..149767bf70521 100644
--- a/library/proc_macro/src/bridge/buffer.rs
+++ b/library/proc_macro/src/bridge/buffer.rs
@@ -119,7 +119,9 @@ impl Write for Buffer {
 }
 
 impl Drop for Buffer {
-    #[inline]
+    // HACK(nbdd0121): Hack to prevent LLVM < 17.0.4 from misoptimising,
+    // change to `#[inline]` if fixed.
+    #[inline(never)]
     fn drop(&mut self) {
         let b = self.take();
         (b.drop)(b);
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 9d6576fa84117..ae444836efa48 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -273,12 +273,12 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![feature(alloc_error_handler)]
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
 #![feature(asm_experimental_arch)]
-#![feature(c_unwind)]
 #![feature(cfg_sanitizer_cfi)]
 #![feature(cfg_target_thread_local)]
 #![feature(cfi_encoding)]
diff --git a/library/unwind/src/lib.rs b/library/unwind/src/lib.rs
index 544d9fbf1ae0f..45a1c334a44dd 100644
--- a/library/unwind/src/lib.rs
+++ b/library/unwind/src/lib.rs
@@ -2,7 +2,7 @@
 #![unstable(feature = "panic_unwind", issue = "32837")]
 #![feature(link_cfg)]
 #![feature(staged_api)]
-#![feature(c_unwind)]
+#![cfg_attr(bootstrap, feature(c_unwind))]
 #![feature(strict_provenance)]
 #![cfg_attr(target_arch = "wasm64", feature(simd_wasm64))]
 #![cfg_attr(not(target_env = "msvc"), feature(libc))]
diff --git a/src/doc/unstable-book/src/language-features/c-unwind.md b/src/doc/unstable-book/src/language-features/c-unwind.md
deleted file mode 100644
index fb32918d5e439..0000000000000
--- a/src/doc/unstable-book/src/language-features/c-unwind.md
+++ /dev/null
@@ -1,26 +0,0 @@
-# `c_unwind`
-
-The tracking issue for this feature is: [#74990]
-
-[#74990]: https://github.com/rust-lang/rust/issues/74990
-
-------------------------
-
-Introduces new ABI strings:
-- "C-unwind"
-- "cdecl-unwind"
-- "stdcall-unwind"
-- "fastcall-unwind"
-- "vectorcall-unwind"
-- "thiscall-unwind"
-- "aapcs-unwind"
-- "win64-unwind"
-- "sysv64-unwind"
-- "system-unwind"
-
-These enable unwinding from other languages (such as C++) into Rust frames and
-from Rust into other languages.
-
-See [RFC 2945] for more information.
-
-[RFC 2945]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.rs b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.rs
index 6d68b9a46d9e3..dc192d0319636 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.rs
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.rs
@@ -1,5 +1,3 @@
-#![feature(c_unwind)]
-
 #[no_mangle]
 extern "C-unwind" fn unwind() {
     panic!();
diff --git a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.rs b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.rs
index e6aff19b02d49..1382e9571f316 100644
--- a/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.rs
+++ b/src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.rs
@@ -4,7 +4,7 @@
 //@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
 //@normalize-stderr-test: "\n +at [^\n]+" -> ""
 //@[definition,both]error-in-other-file: aborted execution
-#![feature(rustc_attrs, c_unwind)]
+#![feature(rustc_attrs)]
 
 #[cfg_attr(any(definition, both), rustc_nounwind)]
 #[no_mangle]
diff --git a/src/tools/miri/tests/fail/panic/bad_unwind.rs b/src/tools/miri/tests/fail/panic/bad_unwind.rs
index 8c8a9f18cdc63..5370485b2a623 100644
--- a/src/tools/miri/tests/fail/panic/bad_unwind.rs
+++ b/src/tools/miri/tests/fail/panic/bad_unwind.rs
@@ -1,5 +1,3 @@
-#![feature(c_unwind)]
-
 //! Unwinding when the caller ABI is "C" (without "-unwind") is UB.
 // The opposite version (callee does not allow unwinding) is impossible to
 // even write: MIR validation catches functions that have `UnwindContinue` but
diff --git a/src/tools/miri/tests/fail/terminate-terminator.rs b/src/tools/miri/tests/fail/terminate-terminator.rs
index 7c6728280305d..465625c757251 100644
--- a/src/tools/miri/tests/fail/terminate-terminator.rs
+++ b/src/tools/miri/tests/fail/terminate-terminator.rs
@@ -7,8 +7,6 @@
 // Enable MIR inlining to ensure that `TerminatorKind::UnwindTerminate` is generated
 // instead of just `UnwindAction::Terminate`.
 
-#![feature(c_unwind)]
-
 struct Foo;
 
 impl Drop for Foo {
diff --git a/src/tools/miri/tests/fail/unwind-action-terminate.rs b/src/tools/miri/tests/fail/unwind-action-terminate.rs
index 86406872c5991..465e07c8db4b8 100644
--- a/src/tools/miri/tests/fail/unwind-action-terminate.rs
+++ b/src/tools/miri/tests/fail/unwind-action-terminate.rs
@@ -3,8 +3,6 @@
 //@normalize-stderr-test: "\| +\^+" -> "| ^"
 //@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
 //@normalize-stderr-test: "\n +at [^\n]+" -> ""
-#![feature(c_unwind)]
-
 extern "C" fn panic_abort() {
     panic!()
 }
diff --git a/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.rs b/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.rs
index 71b799a1f12ba..0e8d45af27fdf 100644
--- a/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.rs
+++ b/src/tools/miri/tests/panic/function_calls/exported_symbol_good_unwind.rs
@@ -2,7 +2,7 @@
 // found in this form" errors works without `-C prefer-dynamic` (`panic!` calls foreign function
 // `__rust_start_panic`).
 // no-prefer-dynamic
-#![feature(c_unwind, unboxed_closures)]
+#![feature(unboxed_closures)]
 
 use std::panic;
 
diff --git a/tests/assembly/asm/aarch64-modifiers.rs b/tests/assembly/asm/aarch64-modifiers.rs
index ffba06ae47bb4..b7ef1d77ea023 100644
--- a/tests/assembly/asm/aarch64-modifiers.rs
+++ b/tests/assembly/asm/aarch64-modifiers.rs
@@ -1,5 +1,5 @@
 //@ assembly-output: emit-asm
-//@ compile-flags: -O
+//@ compile-flags: -O -C panic=abort
 //@ compile-flags: --target aarch64-unknown-linux-gnu
 //@ needs-llvm-components: aarch64
 
diff --git a/tests/assembly/asm/arm-modifiers.rs b/tests/assembly/asm/arm-modifiers.rs
index fa2e75eb35b04..0674e169d72e6 100644
--- a/tests/assembly/asm/arm-modifiers.rs
+++ b/tests/assembly/asm/arm-modifiers.rs
@@ -1,5 +1,5 @@
 //@ assembly-output: emit-asm
-//@ compile-flags: -O
+//@ compile-flags: -O -C panic=abort
 //@ compile-flags: --target armv7-unknown-linux-gnueabihf
 //@ compile-flags: -C target-feature=+neon
 //@ needs-llvm-components: arm
diff --git a/tests/assembly/asm/x86-modifiers.rs b/tests/assembly/asm/x86-modifiers.rs
index 1a92585298d94..c5e393b10564e 100644
--- a/tests/assembly/asm/x86-modifiers.rs
+++ b/tests/assembly/asm/x86-modifiers.rs
@@ -1,6 +1,6 @@
 //@ revisions: x86_64 i686
 //@ assembly-output: emit-asm
-//@ compile-flags: -O
+//@ compile-flags: -O -C panic=abort
 //@[x86_64] compile-flags: --target x86_64-unknown-linux-gnu
 //@[x86_64] needs-llvm-components: x86
 //@[i686] compile-flags: --target i686-unknown-linux-gnu
diff --git a/tests/assembly/simd-bitmask.rs b/tests/assembly/simd-bitmask.rs
index 8264a70685207..cd22ca067061f 100644
--- a/tests/assembly/simd-bitmask.rs
+++ b/tests/assembly/simd-bitmask.rs
@@ -11,7 +11,7 @@
 //@ [aarch64] needs-llvm-components: aarch64
 //@ [aarch64] min-llvm-version: 18.0
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-gather.rs b/tests/assembly/simd-intrinsic-gather.rs
index ef6b597c25f1e..83015f05ab3ee 100644
--- a/tests/assembly/simd-intrinsic-gather.rs
+++ b/tests/assembly/simd-intrinsic-gather.rs
@@ -4,7 +4,7 @@
 //@ [x86-avx512] needs-llvm-components: x86
 //@ [x86-avx512] min-llvm-version: 18.0
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-mask-load.rs b/tests/assembly/simd-intrinsic-mask-load.rs
index 49d231c45f858..d537c143d365b 100644
--- a/tests/assembly/simd-intrinsic-mask-load.rs
+++ b/tests/assembly/simd-intrinsic-mask-load.rs
@@ -6,7 +6,7 @@
 //@ [x86-avx512] compile-flags: -C target-feature=+avx512f,+avx512vl,+avx512bw,+avx512dq
 //@ [x86-avx512] needs-llvm-components: x86
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-mask-reduce.rs b/tests/assembly/simd-intrinsic-mask-reduce.rs
index 72c3f6376e807..dd4dbaeda76c0 100644
--- a/tests/assembly/simd-intrinsic-mask-reduce.rs
+++ b/tests/assembly/simd-intrinsic-mask-reduce.rs
@@ -8,7 +8,7 @@
 //@ [aarch64] needs-llvm-components: aarch64
 //@ [aarch64] min-llvm-version: 18.0
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-mask-store.rs b/tests/assembly/simd-intrinsic-mask-store.rs
index a6611e1c23d5c..5d4c00c382337 100644
--- a/tests/assembly/simd-intrinsic-mask-store.rs
+++ b/tests/assembly/simd-intrinsic-mask-store.rs
@@ -6,7 +6,7 @@
 //@ [x86-avx512] compile-flags: -C target-feature=+avx512f,+avx512vl,+avx512bw,+avx512dq
 //@ [x86-avx512] needs-llvm-components: x86
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-scatter.rs b/tests/assembly/simd-intrinsic-scatter.rs
index 6ffefb0801aec..55095e4cb681f 100644
--- a/tests/assembly/simd-intrinsic-scatter.rs
+++ b/tests/assembly/simd-intrinsic-scatter.rs
@@ -4,7 +4,7 @@
 //@ [x86-avx512] needs-llvm-components: x86
 //@ [x86-avx512] min-llvm-version: 18.0
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/assembly/simd-intrinsic-select.rs b/tests/assembly/simd-intrinsic-select.rs
index 3f36402e3d0d5..4dfc2f9ed1fb2 100644
--- a/tests/assembly/simd-intrinsic-select.rs
+++ b/tests/assembly/simd-intrinsic-select.rs
@@ -9,7 +9,7 @@
 //@ [aarch64] needs-llvm-components: aarch64
 //@ [aarch64] min-llvm-version: 18.0
 //@ assembly-output: emit-asm
-//@ compile-flags: --crate-type=lib -O
+//@ compile-flags: --crate-type=lib -O -C panic=abort
 
 #![feature(no_core, lang_items, repr_simd, intrinsics)]
 #![no_core]
diff --git a/tests/codegen/align-byval-alignment-mismatch.rs b/tests/codegen/align-byval-alignment-mismatch.rs
index 71f2dd42ec222..835cc7393e51e 100644
--- a/tests/codegen/align-byval-alignment-mismatch.rs
+++ b/tests/codegen/align-byval-alignment-mismatch.rs
@@ -1,9 +1,9 @@
 // ignore-tidy-linelength
 //@ revisions:i686-linux x86_64-linux
 
-//@[i686-linux] compile-flags: --target i686-unknown-linux-gnu
+//@[i686-linux] compile-flags: --target i686-unknown-linux-gnu -C panic=abort
 //@[i686-linux] needs-llvm-components: x86
-//@[x86_64-linux] compile-flags: --target x86_64-unknown-linux-gnu
+//@[x86_64-linux] compile-flags: --target x86_64-unknown-linux-gnu -C panic=abort
 //@[x86_64-linux] needs-llvm-components: x86
 
 // Tests that we correctly copy arguments into allocas when the alignment of the byval argument
diff --git a/tests/codegen/avr/avr-func-addrspace.rs b/tests/codegen/avr/avr-func-addrspace.rs
index 2d9efb52c7cfa..708347075640b 100644
--- a/tests/codegen/avr/avr-func-addrspace.rs
+++ b/tests/codegen/avr/avr-func-addrspace.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -O --target=avr-unknown-gnu-atmega328 --crate-type=rlib
+//@ compile-flags: -O --target=avr-unknown-gnu-atmega328 --crate-type=rlib -C panic=abort
 //@ needs-llvm-components: avr
 
 // This test validates that function pointers can be stored in global variables
diff --git a/tests/codegen/catch-unwind.rs b/tests/codegen/catch-unwind.rs
index 4e1f9a88e9573..48ad486fa03a6 100644
--- a/tests/codegen/catch-unwind.rs
+++ b/tests/codegen/catch-unwind.rs
@@ -14,7 +14,6 @@
 //@ ignore-loongarch64 FIXME
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 extern "C" {
     fn bar();
diff --git a/tests/codegen/cffi/c-variadic.rs b/tests/codegen/cffi/c-variadic.rs
index 914d1623ed230..140d2f37f4693 100644
--- a/tests/codegen/cffi/c-variadic.rs
+++ b/tests/codegen/cffi/c-variadic.rs
@@ -4,7 +4,6 @@
 
 #![crate_type = "lib"]
 #![feature(c_variadic)]
-#![feature(c_unwind)]
 #![no_std]
 use core::ffi::VaList;
 
diff --git a/tests/codegen/debuginfo-inline-callsite-location.rs b/tests/codegen/debuginfo-inline-callsite-location.rs
index f690c9c0937ff..aee07b4eb8c68 100644
--- a/tests/codegen/debuginfo-inline-callsite-location.rs
+++ b/tests/codegen/debuginfo-inline-callsite-location.rs
@@ -1,4 +1,4 @@
-//@ compile-flags: -g -O
+//@ compile-flags: -g -O -C panic=abort
 
 // Check that each inline call site for the same function uses the same "sub-program" so that LLVM
 // can correctly merge the debug info if it merges the inlined code (e.g., for merging of tail
diff --git a/tests/codegen/unwind-abis/aapcs-unwind-abi.rs b/tests/codegen/unwind-abis/aapcs-unwind-abi.rs
index 48c7ecf782429..0d9c7757883f7 100644
--- a/tests/codegen/unwind-abis/aapcs-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/aapcs-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: arm
 //@ compile-flags: --target=armv7-unknown-linux-gnueabihf --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/c-unwind-abi-panic-abort.rs b/tests/codegen/unwind-abis/c-unwind-abi-panic-abort.rs
index 8bb2122946fca..8d2745ba2f7ae 100644
--- a/tests/codegen/unwind-abis/c-unwind-abi-panic-abort.rs
+++ b/tests/codegen/unwind-abis/c-unwind-abi-panic-abort.rs
@@ -4,7 +4,6 @@
 // when the code is compiled with `panic=abort`.
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // CHECK: @rust_item_that_can_unwind() unnamed_addr [[ATTR0:#[0-9]+]]
 #[no_mangle]
diff --git a/tests/codegen/unwind-abis/c-unwind-abi.rs b/tests/codegen/unwind-abis/c-unwind-abi.rs
index 99763943a6acf..46c08b5fc4ff4 100644
--- a/tests/codegen/unwind-abis/c-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/c-unwind-abi.rs
@@ -6,7 +6,6 @@
 // to prevent LLVM from inferring the attribute.
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
 #[no_mangle]
diff --git a/tests/codegen/unwind-abis/cdecl-unwind-abi.rs b/tests/codegen/unwind-abis/cdecl-unwind-abi.rs
index 78dbb55b35a21..8e643d6ce4947 100644
--- a/tests/codegen/unwind-abis/cdecl-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/cdecl-unwind-abi.rs
@@ -6,7 +6,6 @@
 // disable optimizations above to prevent LLVM from inferring the attribute.
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
 #[no_mangle]
diff --git a/tests/codegen/unwind-abis/fastcall-unwind-abi.rs b/tests/codegen/unwind-abis/fastcall-unwind-abi.rs
index 3cbeaf51d9600..4c7b2856e2e45 100644
--- a/tests/codegen/unwind-abis/fastcall-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/fastcall-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=i686-pc-windows-msvc --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/nounwind-on-stable-panic-unwind.rs b/tests/codegen/unwind-abis/nounwind-on-stable-panic-unwind.rs
deleted file mode 100644
index a7f7f2fb77f71..0000000000000
--- a/tests/codegen/unwind-abis/nounwind-on-stable-panic-unwind.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-//@ compile-flags: -C opt-level=0
-//@ needs-unwind
-
-#![crate_type = "lib"]
-
-// We disable optimizations to prevent LLVM from inferring the attribute.
-
-extern "C" {
-    fn bar();
-}
-
-// CHECK-NOT: Function Attrs:{{.*}}nounwind
-pub unsafe extern "C" fn foo() {
-    bar();
-}
-
-// Note that this test will get removed when `C-unwind` is fully stabilized
diff --git a/tests/codegen/unwind-abis/nounwind.rs b/tests/codegen/unwind-abis/nounwind.rs
index 80bf8d6709139..e40ed48ca737f 100644
--- a/tests/codegen/unwind-abis/nounwind.rs
+++ b/tests/codegen/unwind-abis/nounwind.rs
@@ -2,7 +2,6 @@
 //@ needs-unwind
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // We disable optimizations to prevent LLVM from inferring the attribute.
 
diff --git a/tests/codegen/unwind-abis/stdcall-unwind-abi.rs b/tests/codegen/unwind-abis/stdcall-unwind-abi.rs
index ffb235cd11681..ffc11d1faef8c 100644
--- a/tests/codegen/unwind-abis/stdcall-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/stdcall-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=i686-pc-windows-msvc --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/system-unwind-abi.rs b/tests/codegen/unwind-abis/system-unwind-abi.rs
index 1dd0e9bbbec7d..5f9102483464b 100644
--- a/tests/codegen/unwind-abis/system-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/system-unwind-abi.rs
@@ -6,7 +6,6 @@
 // optimizations above to prevent LLVM from inferring the attribute.
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // CHECK: @rust_item_that_cannot_unwind() unnamed_addr #0 {
 #[no_mangle]
diff --git a/tests/codegen/unwind-abis/sysv64-unwind-abi.rs b/tests/codegen/unwind-abis/sysv64-unwind-abi.rs
index 9824009dc5592..c869ca7e2b825 100644
--- a/tests/codegen/unwind-abis/sysv64-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/sysv64-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/thiscall-unwind-abi.rs b/tests/codegen/unwind-abis/thiscall-unwind-abi.rs
index a96f4d5a350c1..19b23ee47ba84 100644
--- a/tests/codegen/unwind-abis/thiscall-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/thiscall-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=i686-pc-windows-msvc --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/vectorcall-unwind-abi.rs b/tests/codegen/unwind-abis/vectorcall-unwind-abi.rs
index 9929e3e3703de..b420f67ca9b70 100644
--- a/tests/codegen/unwind-abis/vectorcall-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/vectorcall-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=i686-pc-windows-msvc --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind, abi_vectorcall)]
+#![feature(no_core, lang_items, abi_vectorcall)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-abis/win64-unwind-abi.rs b/tests/codegen/unwind-abis/win64-unwind-abi.rs
index a45a94f628d15..2697d3cbcd68e 100644
--- a/tests/codegen/unwind-abis/win64-unwind-abi.rs
+++ b/tests/codegen/unwind-abis/win64-unwind-abi.rs
@@ -1,7 +1,7 @@
 //@ needs-llvm-components: x86
 //@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=rlib -Cno-prepopulate-passes
 #![no_core]
-#![feature(no_core, lang_items, c_unwind)]
+#![feature(no_core, lang_items)]
 #[lang = "sized"]
 trait Sized {}
 
diff --git a/tests/codegen/unwind-and-panic-abort.rs b/tests/codegen/unwind-and-panic-abort.rs
index 430502308cf0d..8efa140058ad1 100644
--- a/tests/codegen/unwind-and-panic-abort.rs
+++ b/tests/codegen/unwind-and-panic-abort.rs
@@ -1,7 +1,6 @@
 //@ compile-flags: -C panic=abort
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 extern "C-unwind" {
     fn bar();
diff --git a/tests/codegen/unwind-extern-exports.rs b/tests/codegen/unwind-extern-exports.rs
index ea59748b3bcd2..e692fd1a54722 100644
--- a/tests/codegen/unwind-extern-exports.rs
+++ b/tests/codegen/unwind-extern-exports.rs
@@ -2,7 +2,6 @@
 //@ needs-unwind
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 // Make sure these all do *not* get the attribute.
 // We disable optimizations to prevent LLVM from inferring the attribute.
diff --git a/tests/codegen/unwind-extern-imports.rs b/tests/codegen/unwind-extern-imports.rs
index 790e4def8b363..dfae8aae64a51 100644
--- a/tests/codegen/unwind-extern-imports.rs
+++ b/tests/codegen/unwind-extern-imports.rs
@@ -2,7 +2,6 @@
 //@ needs-unwind
 
 #![crate_type = "lib"]
-#![feature(c_unwind)]
 
 extern "C" {
     // CHECK: Function Attrs:{{.*}}nounwind
diff --git a/tests/coverage/abort.cov-map b/tests/coverage/abort.cov-map
index 5673fa98ca606..15156ec9811b1 100644
--- a/tests/coverage/abort.cov-map
+++ b/tests/coverage/abort.cov-map
@@ -1,5 +1,5 @@
 Function name: abort::main
-Raw bytes (89): 0x[01, 01, 0a, 01, 27, 05, 09, 03, 0d, 22, 11, 03, 0d, 03, 0d, 22, 15, 03, 0d, 03, 0d, 05, 09, 0d, 01, 0e, 01, 01, 1b, 03, 02, 0b, 00, 18, 22, 01, 0c, 00, 19, 11, 00, 1a, 02, 0a, 0e, 02, 0a, 00, 0b, 22, 02, 0c, 00, 19, 15, 00, 1a, 00, 31, 1a, 00, 31, 00, 32, 22, 04, 0c, 00, 19, 05, 00, 1a, 00, 31, 09, 00, 31, 00, 32, 27, 01, 09, 00, 17, 0d, 02, 05, 01, 02]
+Raw bytes (89): 0x[01, 01, 0a, 01, 27, 05, 09, 03, 0d, 22, 11, 03, 0d, 03, 0d, 22, 15, 03, 0d, 03, 0d, 05, 09, 0d, 01, 0d, 01, 01, 1b, 03, 02, 0b, 00, 18, 22, 01, 0c, 00, 19, 11, 00, 1a, 02, 0a, 0e, 02, 0a, 00, 0b, 22, 02, 0c, 00, 19, 15, 00, 1a, 00, 31, 1a, 00, 31, 00, 32, 22, 04, 0c, 00, 19, 05, 00, 1a, 00, 31, 09, 00, 31, 00, 32, 27, 01, 09, 00, 17, 0d, 02, 05, 01, 02]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 10
@@ -14,7 +14,7 @@ Number of expressions: 10
 - expression 8 operands: lhs = Expression(0, Add), rhs = Counter(3)
 - expression 9 operands: lhs = Counter(1), rhs = Counter(2)
 Number of file 0 mappings: 13
-- Code(Counter(0)) at (prev + 14, 1) to (start + 1, 27)
+- Code(Counter(0)) at (prev + 13, 1) to (start + 1, 27)
 - Code(Expression(0, Add)) at (prev + 2, 11) to (start + 0, 24)
     = (c0 + (c1 + c2))
 - Code(Expression(8, Sub)) at (prev + 1, 12) to (start + 0, 25)
@@ -36,13 +36,13 @@ Number of file 0 mappings: 13
 - Code(Counter(3)) at (prev + 2, 5) to (start + 1, 2)
 
 Function name: abort::might_abort
-Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 04, 01, 01, 14, 05, 02, 09, 01, 24, 02, 02, 0c, 03, 02]
+Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 03, 01, 01, 14, 05, 02, 09, 01, 24, 02, 02, 0c, 03, 02]
 Number of files: 1
 - file 0 => global file 1
 Number of expressions: 1
 - expression 0 operands: lhs = Counter(0), rhs = Counter(1)
 Number of file 0 mappings: 3
-- Code(Counter(0)) at (prev + 4, 1) to (start + 1, 20)
+- Code(Counter(0)) at (prev + 3, 1) to (start + 1, 20)
 - Code(Counter(1)) at (prev + 2, 9) to (start + 1, 36)
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 3, 2)
     = (c0 - c1)
diff --git a/tests/coverage/abort.coverage b/tests/coverage/abort.coverage
index b658a65625912..29e3ad5eda7aa 100644
--- a/tests/coverage/abort.coverage
+++ b/tests/coverage/abort.coverage
@@ -1,4 +1,3 @@
-   LL|       |#![feature(c_unwind)]
    LL|       |#![allow(unused_assignments)]
    LL|       |
    LL|     12|extern "C" fn might_abort(should_abort: bool) {
diff --git a/tests/coverage/abort.rs b/tests/coverage/abort.rs
index 649e8e52a490e..6c06a3f9d8750 100644
--- a/tests/coverage/abort.rs
+++ b/tests/coverage/abort.rs
@@ -1,4 +1,3 @@
-#![feature(c_unwind)]
 #![allow(unused_assignments)]
 
 extern "C" fn might_abort(should_abort: bool) {
diff --git a/tests/run-make/forced-unwind-terminate-pof/foo.rs b/tests/run-make/forced-unwind-terminate-pof/foo.rs
index 0a51287313f6e..3a84784621708 100644
--- a/tests/run-make/forced-unwind-terminate-pof/foo.rs
+++ b/tests/run-make/forced-unwind-terminate-pof/foo.rs
@@ -1,6 +1,5 @@
 // Tests that forced unwind through POF Rust frames wouldn't trigger our terminating guards.
 
-#![feature(c_unwind)]
 #![no_main]
 
 extern "C-unwind" {
diff --git a/tests/ui/asm/x86_64/may_unwind.rs b/tests/ui/asm/x86_64/may_unwind.rs
index 3b2c1edcd4786..d3a2916df9db6 100644
--- a/tests/ui/asm/x86_64/may_unwind.rs
+++ b/tests/ui/asm/x86_64/may_unwind.rs
@@ -16,7 +16,7 @@ impl Drop for Foo<'_> {
     }
 }
 
-extern "C" fn panicky() {
+extern "C-unwind" fn panicky() {
     resume_unwind(Box::new(()));
 }
 
diff --git a/tests/ui/consts/const-eval/unwind-abort.rs b/tests/ui/consts/const-eval/unwind-abort.rs
index 57959e7db6ad9..26113e238883d 100644
--- a/tests/ui/consts/const-eval/unwind-abort.rs
+++ b/tests/ui/consts/const-eval/unwind-abort.rs
@@ -1,4 +1,4 @@
-#![feature(c_unwind, const_extern_fn)]
+#![feature(const_extern_fn)]
 
 const extern "C" fn foo() {
     panic!() //~ ERROR evaluation of constant value failed
diff --git a/tests/ui/consts/unwind-abort.rs b/tests/ui/consts/unwind-abort.rs
index 35db9152bd551..1dd33f327fb68 100644
--- a/tests/ui/consts/unwind-abort.rs
+++ b/tests/ui/consts/unwind-abort.rs
@@ -1,6 +1,6 @@
 //@ check-pass
 
-#![feature(c_unwind, const_extern_fn)]
+#![feature(const_extern_fn)]
 
 // We don't unwind in const-eval anyways.
 const extern "C" fn foo() {
diff --git a/tests/ui/panics/abort-on-panic.rs b/tests/ui/panics/abort-on-panic.rs
index 5736ecf868566..feccefb253768 100644
--- a/tests/ui/panics/abort-on-panic.rs
+++ b/tests/ui/panics/abort-on-panic.rs
@@ -4,7 +4,6 @@
 //@[next] compile-flags: -Znext-solver
 
 #![allow(unused_must_use)]
-#![feature(c_unwind)]
 #![feature(panic_always_abort)]
 // Since we mark some ABIs as "nounwind" to LLVM, we must make sure that
 // we never unwind through them.
diff --git a/tests/ui/panics/panic-in-ffi.rs b/tests/ui/panics/panic-in-ffi.rs
index 6f54acb3e045d..88f45f9a871d7 100644
--- a/tests/ui/panics/panic-in-ffi.rs
+++ b/tests/ui/panics/panic-in-ffi.rs
@@ -7,7 +7,6 @@
 //@ normalize-stderr-test: "(core/src/panicking\.rs):[0-9]+:[0-9]+" -> "$1:$$LINE:$$COL"
 //@ needs-unwind
 //@ ignore-emscripten "RuntimeError" junk in output
-#![feature(c_unwind)]
 
 extern "C" fn panic_in_ffi() {
     panic!("Test");
diff --git a/tests/ui/panics/panic-in-ffi.run.stderr b/tests/ui/panics/panic-in-ffi.run.stderr
index a92a66c57fd7d..596355399c801 100644
--- a/tests/ui/panics/panic-in-ffi.run.stderr
+++ b/tests/ui/panics/panic-in-ffi.run.stderr
@@ -1,4 +1,4 @@
-thread 'main' panicked at $DIR/panic-in-ffi.rs:13:5:
+thread 'main' panicked at $DIR/panic-in-ffi.rs:12:5:
 Test
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 thread 'main' panicked at library/core/src/panicking.rs:$LINE:$COL:
diff --git a/tests/ui/unwind-abis/feature-gate-c_unwind.rs b/tests/ui/unwind-abis/feature-gate-c_unwind.rs
deleted file mode 100644
index 28ef7d57788ee..0000000000000
--- a/tests/ui/unwind-abis/feature-gate-c_unwind.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-//@ ignore-test
-
-// After partial stabilisation, `c_unwind` only contains codegen behaviour changes
-// and are tested in `src/test/codegen/unwind-abis`