Auto merge of #104999 - saethlin:immediate-abort-inlining, r=thomcc
Adjust inlining attributes around panic_immediate_abort The goal of `panic_immediate_abort` is to permit the panic runtime and formatting code paths to be optimized away. But while poking through some disassembly of a small program compiled with that option, I found that was not the case. Enabling LTO did address that specific issue, but enabling LTO is a steep price to pay for this feature doing its job. This PR fixes that, by tweaking two things: * All the slice indexing functions that we `const_eval_select` on get `#[inline]`. `objdump -dC` told me that originally some `_ct` functions could end up in an executable. I won't pretend to understand what's going on there. * Normalize attributes across all `panic!` wrappers: use `inline(never) + cold` normally, and `inline` when `panic_immediate_abort` is enabled. But also, with LTO and `panic_immediate_abort` enabled, this patch knocks ~709 kB out of the `.text` segment of `librustc_driver.so`. That is slightly surprising to me, my best theory is that this shifts some inlining earlier in compilation, enabling some subsequent optimizations. The size improvement of `librustc_driver.so` with `panic_immediate_abort` due to this patch is greater with LTO than without LTO, which I suppose backs up this theory. I do not know how to test this. I would quite like to, because I think what this is solving was an accidental regression. This only works with `-Zbuild-std` which is a cargo flag, and thus can't be used in a rustc codegen test. r? `@thomcc` --- I do not seriously think anyone is going to use a compiler built with `panic_immediate_abort`, but I wanted a big complicated Rust program to try this out on, and the compiler is such.
This commit is contained in:
bors
commit
32e613bbaa
3 changed files with 26 additions and 24 deletions
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@ -38,10 +38,9 @@ use crate::panic::{Location, PanicInfo};
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/// site as much as possible (so that `panic!()` has as low an impact
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/// on (e.g.) the inlining of other functions as possible), by moving
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/// the actual formatting into this shared place.
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#[cold]
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// If panic_immediate_abort, inline the abort call,
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// otherwise avoid inlining because of it is cold path.
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[lang = "panic_fmt"] // needed for const-evaluated panics
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@ -67,8 +66,7 @@ pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
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/// Like panic_fmt, but without unwinding and track_caller to reduce the impact on codesize.
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/// Also just works on `str`, as a `fmt::Arguments` needs more space to be passed.
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#[cold]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[rustc_nounwind]
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pub fn panic_str_nounwind(msg: &'static str) -> ! {
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@ -96,10 +94,9 @@ pub fn panic_str_nounwind(msg: &'static str) -> ! {
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// above.
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/// The underlying implementation of libcore's `panic!` macro when no formatting is used.
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#[cold]
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// never inline unless panic_immediate_abort to avoid code
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// bloat at the call sites as much as possible
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[rustc_const_unstable(feature = "core_panic", issue = "none")]
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@ -138,8 +135,8 @@ pub const fn panic_display<T: fmt::Display>(x: &T) -> ! {
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panic_fmt(format_args!("{}", *x));
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}
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#[cold]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[lang = "panic_bounds_check"] // needed by codegen for panic on OOB array/slice access
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fn panic_bounds_check(index: usize, len: usize) -> ! {
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@ -154,8 +151,8 @@ fn panic_bounds_check(index: usize, len: usize) -> ! {
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///
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/// This function is called directly by the codegen backend, and must not have
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/// any extra arguments (including those synthesized by track_caller).
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#[cold]
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#[inline(never)]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[lang = "panic_no_unwind"] // needed by codegen for panic in nounwind function
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#[rustc_nounwind]
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fn panic_no_unwind() -> ! {
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@ -185,7 +182,8 @@ pub enum AssertKind {
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}
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/// Internal function for `assert_eq!` and `assert_ne!` macros
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#[cold]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[doc(hidden)]
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pub fn assert_failed<T, U>(
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@ -202,7 +200,8 @@ where
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}
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/// Internal function for `assert_match!`
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#[cold]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[doc(hidden)]
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pub fn assert_matches_failed<T: fmt::Debug + ?Sized>(
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@ -221,6 +220,8 @@ pub fn assert_matches_failed<T: fmt::Debug + ?Sized>(
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}
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/// Non-generic version of the above functions, to avoid code bloat.
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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fn assert_failed_inner(
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kind: AssertKind,
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@ -31,9 +31,8 @@ where
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}
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}
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[cold]
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#[track_caller]
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#[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
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const fn slice_start_index_len_fail(index: usize, len: usize) -> ! {
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@ -48,19 +47,20 @@ const fn slice_start_index_len_fail(index: usize, len: usize) -> ! {
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}
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// FIXME const-hack
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#[inline]
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#[track_caller]
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fn slice_start_index_len_fail_rt(index: usize, len: usize) -> ! {
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panic!("range start index {index} out of range for slice of length {len}");
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}
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#[inline]
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#[track_caller]
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const fn slice_start_index_len_fail_ct(_: usize, _: usize) -> ! {
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panic!("slice start index is out of range for slice");
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}
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[cold]
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#[track_caller]
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#[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
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const fn slice_end_index_len_fail(index: usize, len: usize) -> ! {
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@ -71,19 +71,20 @@ const fn slice_end_index_len_fail(index: usize, len: usize) -> ! {
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}
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// FIXME const-hack
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#[inline]
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#[track_caller]
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fn slice_end_index_len_fail_rt(index: usize, len: usize) -> ! {
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panic!("range end index {index} out of range for slice of length {len}");
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}
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#[inline]
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#[track_caller]
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const fn slice_end_index_len_fail_ct(_: usize, _: usize) -> ! {
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panic!("slice end index is out of range for slice");
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}
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[cold]
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#[track_caller]
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#[rustc_const_unstable(feature = "const_slice_index", issue = "none")]
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const fn slice_index_order_fail(index: usize, end: usize) -> ! {
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@ -92,27 +93,27 @@ const fn slice_index_order_fail(index: usize, end: usize) -> ! {
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}
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// FIXME const-hack
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#[inline]
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#[track_caller]
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fn slice_index_order_fail_rt(index: usize, end: usize) -> ! {
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panic!("slice index starts at {index} but ends at {end}");
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}
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#[inline]
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#[track_caller]
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const fn slice_index_order_fail_ct(_: usize, _: usize) -> ! {
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panic!("slice index start is larger than end");
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}
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[cold]
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#[track_caller]
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const fn slice_start_index_overflow_fail() -> ! {
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panic!("attempted to index slice from after maximum usize");
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}
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[cold]
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#[track_caller]
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const fn slice_end_index_overflow_fail() -> ! {
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panic!("attempted to index slice up to maximum usize");
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@ -594,8 +594,8 @@ pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! {
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// lang item for CTFE panic support
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// never inline unless panic_immediate_abort to avoid code
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// bloat at the call sites as much as possible
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
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#[cold]
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#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
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#[cfg_attr(feature = "panic_immediate_abort", inline)]
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#[track_caller]
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#[rustc_do_not_const_check] // hooked by const-eval
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pub const fn begin_panic<M: Any + Send>(msg: M) -> ! {
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