apply #[optimize(size)] to #[cold] ones and part of the panick machinery

library/std/src/lib.rs

@@ -306,10 +306,12 @@
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(no_sanitize)]
+#![feature(optimize_attribute)]
 #![feature(prelude_import)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
 #![feature(staged_api)]
+#![feature(stmt_expr_attributes)]
 #![feature(thread_local)]
 #![feature(try_blocks)]
 #![feature(type_alias_impl_trait)]

library/std/src/panicking.rs

@@ -231,6 +231,7 @@ where
 }
 
 /// The default panic handler.
+#[optimize(size)]
 fn default_hook(info: &PanicHookInfo<'_>) {
     // If this is a double panic, make sure that we print a backtrace
     // for this panic. Otherwise only print it if logging is enabled.
@@ -249,7 +250,8 @@ fn default_hook(info: &PanicHookInfo<'_>) {
     let thread = thread::try_current();
     let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>");
 
-    let write = |err: &mut dyn crate::io::Write| {
+    let write = #[optimize(size)]
+    |err: &mut dyn crate::io::Write| {
         // Use a lock to prevent mixed output in multithreading context.
         // Some platforms also require it when printing a backtrace, like `SymFromAddr` on Windows.
         let mut lock = backtrace::lock();
@@ -527,6 +529,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     // optimizer (in most cases this function is not inlined even as a normal,
     // non-cold function, though, as of the writing of this comment).
     #[cold]
+    #[optimize(size)]
     unsafe fn cleanup(payload: *mut u8) -> Box<dyn Any + Send + 'static> {
         // SAFETY: The whole unsafe block hinges on a correct implementation of
         // the panic handler `__rust_panic_cleanup`. As such we can only
@@ -686,7 +689,7 @@ pub fn begin_panic_handler(info: &core::panic::PanicInfo<'_>) -> ! {
 // lang item for CTFE panic support
 // never inline unless panic_immediate_abort to avoid code
 // bloat at the call sites as much as possible
-#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold, optimize(size))]
 #[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[track_caller]
 #[rustc_do_not_const_check] // hooked by const-eval
@@ -756,6 +759,7 @@ fn payload_as_str(payload: &dyn Any) -> &str {
 /// Executes the primary logic for a panic, including checking for recursive
 /// panics, panic hooks, and finally dispatching to the panic runtime to either
 /// abort or unwind.
+#[optimize(size)]
 fn rust_panic_with_hook(
     payload: &mut dyn PanicPayload,
     location: &Location<'_>,

library/std/src/sync/once_lock.rs

@@ -498,6 +498,7 @@ impl<T> OnceLock<T> {
     }
 
     #[cold]
+    #[optimize(size)]
     fn initialize<F, E>(&self, f: F) -> Result<(), E>
     where
         F: FnOnce() -> Result<T, E>,