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Auto merge of rust-lang#129063 - the8472:cold-opt-size, r=Amanieu
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Apply size optimizations to panic machinery and some cold functions

* std dependencies gimli and addr2line are now built with opt-level=s
* various panic-related methods and `#[cold]` methods are now marked `#[optimize(size)]`

Panics should be cold enough that it doesn't make sense to optimize them for speed. The only tradeoff here is if someone does a lot of backtrace captures (without panics) and printing then the opt-level change might impact their perf.

Seems to be the first use of the optimize attribute. Tracking issue rust-lang#54882
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bors committed Sep 2, 2024
2 parents 94885bc + 79b5cfd commit e71f952
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Showing 10 changed files with 26 additions and 9 deletions.
2 changes: 2 additions & 0 deletions library/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -31,8 +31,10 @@ codegen-units = 10000
# helps to improve link times a little bit.
[profile.release.package]
addr2line.debug = 0
addr2line.opt-level = "s"
adler.debug = 0
gimli.debug = 0
gimli.opt-level = "s"
miniz_oxide.debug = 0
object.debug = 0
rustc-demangle.debug = 0
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1 change: 1 addition & 0 deletions library/alloc/src/alloc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,7 @@ extern "Rust" {
#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
#[cfg(all(not(no_global_oom_handling), not(test)))]
#[cold]
#[optimize(size)]
pub const fn handle_alloc_error(layout: Layout) -> ! {
const fn ct_error(_: Layout) -> ! {
panic!("allocation failed");
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1 change: 1 addition & 0 deletions library/alloc/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -183,6 +183,7 @@
#![feature(multiple_supertrait_upcastable)]
#![feature(negative_impls)]
#![feature(never_type)]
#![feature(optimize_attribute)]
#![feature(rustc_allow_const_fn_unstable)]
#![feature(rustc_attrs)]
#![feature(slice_internals)]
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1 change: 1 addition & 0 deletions library/alloc/src/raw_vec.rs
Original file line number Diff line number Diff line change
Expand Up @@ -782,6 +782,7 @@ where
// Central function for reserve error handling.
#[cfg(not(no_global_oom_handling))]
#[cold]
#[optimize(size)]
fn handle_error(e: TryReserveError) -> ! {
match e.kind() {
CapacityOverflow => capacity_overflow(),
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4 changes: 4 additions & 0 deletions library/alloc/src/vec/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1519,6 +1519,7 @@ impl<T, A: Allocator> Vec<T, A> {
#[cold]
#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
#[track_caller]
#[optimize(size)]
fn assert_failed(index: usize, len: usize) -> ! {
panic!("swap_remove index (is {index}) should be < len (is {len})");
}
Expand Down Expand Up @@ -1567,6 +1568,7 @@ impl<T, A: Allocator> Vec<T, A> {
#[cold]
#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
#[track_caller]
#[optimize(size)]
fn assert_failed(index: usize, len: usize) -> ! {
panic!("insertion index (is {index}) should be <= len (is {len})");
}
Expand Down Expand Up @@ -1629,6 +1631,7 @@ impl<T, A: Allocator> Vec<T, A> {
#[cold]
#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
#[track_caller]
#[optimize(size)]
fn assert_failed(index: usize, len: usize) -> ! {
panic!("removal index (is {index}) should be < len (is {len})");
}
Expand Down Expand Up @@ -2317,6 +2320,7 @@ impl<T, A: Allocator> Vec<T, A> {
#[cold]
#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
#[track_caller]
#[optimize(size)]
fn assert_failed(at: usize, len: usize) -> ! {
panic!("`at` split index (is {at}) should be <= len (is {len})");
}
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1 change: 1 addition & 0 deletions library/core/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -234,6 +234,7 @@
#![feature(never_type)]
#![feature(no_core)]
#![feature(no_sanitize)]
#![feature(optimize_attribute)]
#![feature(prelude_import)]
#![feature(repr_simd)]
#![feature(rustc_allow_const_fn_unstable)]
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14 changes: 7 additions & 7 deletions library/core/src/panicking.rs
Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,7 @@ pub const fn panic_display<T: fmt::Display>(x: &T) -> ! {
panic_fmt(format_args!("{}", *x));
}

#[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]
#[lang = "panic_bounds_check"] // needed by codegen for panic on OOB array/slice access
Expand All @@ -276,7 +276,7 @@ fn panic_bounds_check(index: usize, len: usize) -> ! {
panic!("index out of bounds: the len is {len} but the index is {index}")
}

#[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]
#[lang = "panic_misaligned_pointer_dereference"] // needed by codegen for panic on misaligned pointer deref
Expand All @@ -301,7 +301,7 @@ fn panic_misaligned_pointer_dereference(required: usize, found: usize) -> ! {
///
/// This function is called directly by the codegen backend, and must not have
/// any extra arguments (including those synthesized by track_caller).
#[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)]
#[lang = "panic_cannot_unwind"] // needed by codegen for panic in nounwind function
#[rustc_nounwind]
Expand All @@ -317,7 +317,7 @@ fn panic_cannot_unwind() -> ! {
///
/// This function is called directly by the codegen backend, and must not have
/// any extra arguments (including those synthesized by track_caller).
#[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)]
#[lang = "panic_in_cleanup"] // needed by codegen for panic in nounwind function
#[rustc_nounwind]
Expand Down Expand Up @@ -350,7 +350,7 @@ pub enum AssertKind {
}

/// Internal function for `assert_eq!` and `assert_ne!` macros
#[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]
#[doc(hidden)]
Expand All @@ -368,7 +368,7 @@ where
}

/// Internal function for `assert_match!`
#[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]
#[doc(hidden)]
Expand All @@ -388,7 +388,7 @@ pub fn assert_matches_failed<T: fmt::Debug + ?Sized>(
}

/// Non-generic version of the above functions, to avoid code bloat.
#[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]
fn assert_failed_inner(
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2 changes: 2 additions & 0 deletions library/std/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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)]
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8 changes: 6 additions & 2 deletions library/std/src/panicking.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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();
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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<'_>,
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1 change: 1 addition & 0 deletions library/std/src/sync/once_lock.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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>,
Expand Down

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