Rollup merge of #152322 - Zalathar:core-intrinsics, r=fmease

Replace some `feature(core_intrinsics)` with stable hints

I noticed that some compiler crates use `feature(core_intrinsics)` for optimization hints, when they could potentially be using stable `std::hint` functions instead.

This PR replaces the occurrences in `rustc_arena` and `rustc_data_structures`.

compiler/rustc_arena/src/lib.rs

@@ -13,7 +13,6 @@
 #![cfg_attr(test, feature(test))]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![doc(test(no_crate_inject, attr(deny(warnings), allow(internal_features))))]
-#![feature(core_intrinsics)]
 #![feature(decl_macro)]
 #![feature(dropck_eyepatch)]
 #![feature(never_type)]
@@ -26,7 +25,7 @@ use std::cell::{Cell, RefCell};
 use std::marker::PhantomData;
 use std::mem::{self, MaybeUninit};
 use std::ptr::{self, NonNull};
-use std::{cmp, intrinsics, slice};
+use std::{cmp, hint, slice};
 
 use smallvec::SmallVec;
 
@@ -452,7 +451,7 @@ impl DroplessArena {
             let bytes = align_up(layout.size(), DROPLESS_ALIGNMENT);
 
             // Tell LLVM that `end` is aligned to DROPLESS_ALIGNMENT.
-            unsafe { intrinsics::assume(end == align_down(end, DROPLESS_ALIGNMENT)) };
+            unsafe { hint::assert_unchecked(end == align_down(end, DROPLESS_ALIGNMENT)) };
 
             if let Some(sub) = end.checked_sub(bytes) {
                 let new_end = align_down(sub, layout.align());

compiler/rustc_data_structures/src/lib.rs

@@ -10,6 +10,7 @@
 #![allow(internal_features)]
 #![allow(rustc::default_hash_types)]
 #![allow(rustc::potential_query_instability)]
+#![cfg_attr(bootstrap, feature(cold_path))]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![feature(allocator_api)]
 #![feature(ascii_char)]
@@ -19,7 +20,6 @@
 #![feature(cfg_select)]
 #![feature(const_default)]
 #![feature(const_trait_impl)]
-#![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(extend_one)]
 #![feature(file_buffered)]

compiler/rustc_data_structures/src/profiling.rs

@@ -85,12 +85,11 @@ use std::borrow::Borrow;
 use std::collections::hash_map::Entry;
 use std::error::Error;
 use std::fmt::Display;
-use std::intrinsics::unlikely;
 use std::path::Path;
 use std::sync::Arc;
 use std::sync::atomic::Ordering;
 use std::time::{Duration, Instant};
-use std::{fs, process};
+use std::{fs, hint, process};
 
 pub use measureme::EventId;
 use measureme::{EventIdBuilder, Profiler, SerializableString, StringId};
@@ -427,7 +426,8 @@ impl SelfProfilerRef {
                     .unwrap()
                     .increment_query_cache_hit_counters(QueryInvocationId(query_invocation_id.0));
             }
-            if unlikely(profiler_ref.event_filter_mask.contains(EventFilter::QUERY_CACHE_HITS)) {
+            if profiler_ref.event_filter_mask.contains(EventFilter::QUERY_CACHE_HITS) {
+                hint::cold_path();
                 profiler_ref.instant_query_event(
                     |profiler| profiler.query_cache_hit_event_kind,
                     query_invocation_id,
@@ -437,7 +437,8 @@ impl SelfProfilerRef {
 
         // We check both kinds of query cache hit events at once, to reduce overhead in the
         // common case (with self-profile disabled).
-        if unlikely(self.event_filter_mask.intersects(EventFilter::QUERY_CACHE_HIT_COMBINED)) {
+        if self.event_filter_mask.intersects(EventFilter::QUERY_CACHE_HIT_COMBINED) {
+            hint::cold_path();
             cold_call(self, query_invocation_id);
         }
     }

compiler/rustc_data_structures/src/sync/freeze.rs

@@ -1,5 +1,5 @@
 use std::cell::UnsafeCell;
-use std::intrinsics::likely;
+use std::hint;
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
 use std::ptr::NonNull;
@@ -60,10 +60,11 @@ impl<T> FreezeLock<T> {
     /// Get the inner value if frozen.
     #[inline]
     pub fn get(&self) -> Option<&T> {
-        if likely(self.frozen.load(Ordering::Acquire)) {
+        if self.frozen.load(Ordering::Acquire) {
             // SAFETY: This is frozen so the data cannot be modified.
             unsafe { Some(&*self.data.get()) }
         } else {
+            hint::cold_path();
             None
         }
     }

compiler/rustc_data_structures/src/sync/lock.rs

@@ -1,7 +1,7 @@
 //! This module implements a lock which only uses synchronization if `might_be_dyn_thread_safe` is true.
 //! It implements `DynSend` and `DynSync` instead of the typical `Send` and `Sync` traits.
 
-use std::fmt;
+use std::{fmt, hint};
 
 #[derive(Clone, Copy, PartialEq)]
 pub enum Mode {
@@ -10,7 +10,6 @@ pub enum Mode {
 }
 
 use std::cell::{Cell, UnsafeCell};
-use std::intrinsics::unlikely;
 use std::marker::PhantomData;
 use std::mem::ManuallyDrop;
 use std::ops::{Deref, DerefMut};
@@ -92,7 +91,8 @@ pub struct Lock<T> {
 impl<T> Lock<T> {
     #[inline(always)]
     pub fn new(inner: T) -> Self {
-        let (mode, mode_union) = if unlikely(mode::might_be_dyn_thread_safe()) {
+        let (mode, mode_union) = if mode::might_be_dyn_thread_safe() {
+            hint::cold_path();
             // Create the lock with synchronization enabled using the `RawMutex` type.
             (Mode::Sync, ModeUnion { sync: ManuallyDrop::new(RawMutex::INIT) })
         } else {
@@ -150,7 +150,8 @@ impl<T> Lock<T> {
         unsafe {
             match mode {
                 Mode::NoSync => {
-                    if unlikely(self.mode_union.no_sync.replace(LOCKED) == LOCKED) {
+                    if self.mode_union.no_sync.replace(LOCKED) == LOCKED {
+                        hint::cold_path();
                         lock_held()
                     }
                 }