Rollup merge of #102232 - Urgau:stabilize-bench_black_box, r=TaKO8Ki

Stabilize bench_black_box

This PR stabilize `feature(bench_black_box)`.

```rust
pub fn black_box<T>(dummy: T) -> T;
```

The FCP was completed in #64102.

`@rustbot` label +T-libs-api -T-libs

compiler/rustc_codegen_cranelift/example/std_example.rs

@@ -1,4 +1,4 @@
-#![feature(core_intrinsics, generators, generator_trait, is_sorted, bench_black_box)]
+#![feature(core_intrinsics, generators, generator_trait, is_sorted)]
 
 #[cfg(target_arch = "x86_64")]
 use std::arch::x86_64::*;

compiler/rustc_codegen_gcc/tests/run/int.rs

@@ -3,7 +3,7 @@
 // Run-time:
 //   status: 0
 
-#![feature(bench_black_box, const_black_box, core_intrinsics, start)]
+#![feature(const_black_box, core_intrinsics, start)]
 
 #![no_std]
 

compiler/rustc_index/src/lib.rs

@@ -1,7 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(allow_internal_unstable)]
-#![feature(bench_black_box)]
 #![feature(extend_one)]
 #![feature(min_specialization)]
 #![feature(new_uninit)]

library/alloc/tests/lib.rs

@@ -41,7 +41,6 @@
 #![feature(pointer_is_aligned)]
 #![feature(slice_flatten)]
 #![feature(thin_box)]
-#![feature(bench_black_box)]
 #![feature(strict_provenance)]
 #![feature(once_cell)]
 #![feature(drain_keep_rest)]

library/core/src/hint.rs

@@ -217,7 +217,7 @@ pub fn spin_loop() {
 ///
 /// [`std::convert::identity`]: crate::convert::identity
 #[inline]
-#[unstable(feature = "bench_black_box", issue = "64102")]
+#[stable(feature = "bench_black_box", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_const_unstable(feature = "const_black_box", issue = "none")]
 pub const fn black_box<T>(dummy: T) -> T {
     crate::intrinsics::black_box(dummy)

library/core/tests/lib.rs

@@ -2,7 +2,6 @@
 #![feature(array_chunks)]
 #![feature(array_methods)]
 #![feature(array_windows)]
-#![feature(bench_black_box)]
 #![feature(bigint_helper_methods)]
 #![feature(cell_update)]
 #![feature(const_assume)]

library/std/src/lib.rs

@@ -348,7 +348,6 @@
 #![feature(trace_macros)]
 //
 // Only used in tests/benchmarks:
-#![feature(bench_black_box)]
 //
 // Only for const-ness:
 #![feature(const_io_structs)]

library/test/src/lib.rs

@@ -15,7 +15,6 @@
 
 #![unstable(feature = "test", issue = "50297")]
 #![doc(test(attr(deny(warnings))))]
-#![feature(bench_black_box)]
 #![feature(internal_output_capture)]
 #![feature(staged_api)]
 #![feature(process_exitcode_internals)]

src/test/incremental/spans_significant_w_panic.rs

@@ -8,7 +8,6 @@
 // compile-flags: -C overflow-checks=on -Z query-dep-graph
 
 #![feature(rustc_attrs)]
-#![feature(bench_black_box)]
 #![rustc_partition_codegened(module = "spans_significant_w_panic", cfg = "rpass2")]
 #![rustc_partition_codegened(module = "spans_significant_w_panic", cfg = "rpass4")]
 

src/test/ui/box/issue-95036.rs

@@ -1,7 +1,7 @@
 // compile-flags: -O
 // build-pass
 
-#![feature(allocator_api, bench_black_box)]
+#![feature(allocator_api)]
 
 #[inline(never)]
 pub fn by_ref(node: &mut Box<[u8; 1], &std::alloc::Global>) {

src/test/ui/consts/cast-discriminant-zst-enum.rs

@@ -1,6 +1,5 @@
 // run-pass
 // Test a ZST enum whose dicriminant is ~0i128. This caused an ICE when casting to an i32.
-#![feature(bench_black_box)]
 use std::hint::black_box;
 
 #[derive(Copy, Clone)]

src/test/ui/consts/const_discriminant.rs

@@ -1,6 +1,5 @@
 // run-pass
 #![feature(const_discriminant)]
-#![feature(bench_black_box)]
 #![allow(dead_code)]
 
 use std::mem::{discriminant, Discriminant};

src/test/ui/issues/issue-99838.rs

@@ -1,5 +1,5 @@
 // run-pass
-#![feature(bench_black_box)]
+
 use std::hint;
 
 struct U16(u16);

src/test/ui/oom_unwind.rs

@@ -4,8 +4,6 @@
 // needs-unwind
 // only-linux
 
-#![feature(bench_black_box)]
-
 use std::hint::black_box;
 use std::mem::forget;
 use std::panic::catch_unwind;

src/test/ui/process/process-panic-after-fork.rs

@@ -7,7 +7,6 @@
 // ignore-sgx no processes
 // ignore-android: FIXME(#85261)
 
-#![feature(bench_black_box)]
 #![feature(rustc_private)]
 #![feature(never_type)]
 #![feature(panic_always_abort)]

src/test/ui/sanitize/address.rs

@@ -5,9 +5,7 @@
 //
 // run-fail
 // error-pattern: AddressSanitizer: stack-buffer-overflow
-// error-pattern: 'xs' (line 15) <== Memory access at offset
-
-#![feature(bench_black_box)]
+// error-pattern: 'xs' (line 13) <== Memory access at offset
 
 use std::hint::black_box;
 

src/test/ui/sanitize/hwaddress.rs

@@ -10,8 +10,6 @@
 // run-fail
 // error-pattern: HWAddressSanitizer: tag-mismatch
 
-#![feature(bench_black_box)]
-
 use std::hint::black_box;
 
 fn main() {

src/test/ui/sanitize/leak.rs

@@ -6,8 +6,6 @@
 // run-fail
 // error-pattern: LeakSanitizer: detected memory leaks
 
-#![feature(bench_black_box)]
-
 use std::hint::black_box;
 use std::mem;
 

src/test/ui/sanitize/memory-eager.rs

@@ -17,7 +17,6 @@
 
 #![feature(core_intrinsics)]
 #![feature(start)]
-#![feature(bench_black_box)]
 
 use std::hint::black_box;
 use std::mem::MaybeUninit;

src/test/ui/sanitize/memory.rs

@@ -16,7 +16,6 @@
 
 #![feature(core_intrinsics)]
 #![feature(start)]
-#![feature(bench_black_box)]
 #![allow(invalid_value)]
 
 use std::hint::black_box;

src/tools/miri/tests/fail/invalid_bool.rs

@@ -1,7 +1,7 @@
 // Validation makes this fail in the wrong place
 // Make sure we find these even with many checks disabled.
 //@compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
-#![feature(bench_black_box)]
+
 
 fn main() {
     let b = unsafe { std::mem::transmute::<u8, bool>(2) };

src/tools/miri/tests/pass/float.rs

@@ -1,4 +1,4 @@
-#![feature(stmt_expr_attributes, bench_black_box)]
+#![feature(stmt_expr_attributes)]
 #![allow(arithmetic_overflow)]
 use std::fmt::Debug;
 use std::hint::black_box;

src/tools/miri/tests/pass/u128.rs

@@ -1,4 +1,3 @@
-#![feature(bench_black_box)]
 use std::hint::black_box as b;
 
 fn main() {