Some functions in `core::sync` are annotated to only support targets with 8-bit atomic support

[tomerze]

This issue was discussed at #106795
and at #106796 (comment)

Some functions in core::sync are defined to only compile if the target has 8-bit atomic support. While they should be compiled for all targets with atomic support.

This can cause unnecessary compilation issues when using a custom target json.

This can probably be solved by changing the definitions to

#[cfg(any(
    target_has_atomic = "8",
    target_has_atomic = "16",
    target_has_atomic = "32",
    target_has_atomic = "64",
    target_has_atomic = "128",
    target_has_atomic = "ptr"
))]

from

#[cfg(target_has_atomic = "8")]

like you can see at vadorovsky@041978b

Examples:

rust/library/core/src/sync/atomic.rs

Lines 3014 to 3016 in bfffe40

	#[cfg(target_has_atomic = "8")]
	#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
	unsafe fn atomic_add<T: Copy>(dst: *mut T, val: T, order: Ordering) -> T {

rust/library/core/src/sync/atomic.rs

Lines 3047 to 3049 in bfffe40

	#[cfg(target_has_atomic = "8")]
	#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
	unsafe fn atomic_compare_exchange<T: Copy>(

rust/library/core/src/sync/atomic.rs

Lines 3133 to 3135 in bfffe40

	#[cfg(target_has_atomic = "8")]
	#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
	unsafe fn atomic_nand<T: Copy>(dst: *mut T, val: T, order: Ordering) -> T {

@vadorovsky @alessandrod

[vadorovsky]

Thanks for creating the issue! I will submit a PR soon (I'm AFK now).