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Ignore ALWAYS_ABORT_FLAG in count_is_zero fast path #106197

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Ignore ALWAYS_ABORT_FLAG in count_is_zero fast path #106197

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6 changes: 5 additions & 1 deletion library/std/src/panicking.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -371,11 +371,15 @@ pub mod panic_count {
#[must_use]
#[inline]
pub fn count_is_zero() -> bool {
if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) & !ALWAYS_ABORT_FLAG == 0 {
if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) == 0 {
// Fast path: if `GLOBAL_PANIC_COUNT` is zero, all threads
// (including the current one) will have `LOCAL_PANIC_COUNT`
// equal to zero, so TLS access can be avoided.
//
// `ALWAYS_ABORT_FLAG` is ignored intentionally to improve the common
// case. If `ALWAYS_ABORT_FLAG` is set, then `GLOBAL_PANIC_COUNT` will
// not be equal to zero, and the slow path will be taken.
//
// In terms of performance, a relaxed atomic load is similar to a normal
// aligned memory read (e.g., a mov instruction in x86), but with some
// compiler optimization restrictions. On the other hand, a TLS access
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