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core: Support variety of atomic widths in width-agnostic functions #106856

Merged
merged 2 commits into from
Jan 27, 2023
Merged

core: Support variety of atomic widths in width-agnostic functions #106856

merged 2 commits into from
Jan 27, 2023

Commits on Jan 25, 2023

  1. Add target_has_atomic* symbols if any atomic width is supported 

    Atomic operations for different widths (8-bit, 16-bit, 32-bit etc.) are
guarded by `target_has_atomic = "value"` symbol (i.e. `target_has_atomic
= "8"`) (and the other derivatives), but before this change, there was
no width-agnostic symbol indicating a general availability of atomic
operations.

This change introduces:

* `target_has_atomic_load_store` symbol when atomics for any integer
  width are supported by the target.
* `target_has_atomic` symbol when also CAS is supported.

Fixes rust-lang#106845

Signed-off-by: Michal Rostecki <[email protected]>
    @vadorovsky
    vadorovsky committed Jan 25, 2023
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  2. core: Support variety of atomic widths in width-agnostic functions 

    Before this change, the following functions and macros were annotated
with `#[cfg(target_has_atomic = "8")]` or
`#[cfg(target_has_atomic_load_store = "8")]`:

* `atomic_int`
* `strongest_failure_ordering`
* `atomic_swap`
* `atomic_add`
* `atomic_sub`
* `atomic_compare_exchange`
* `atomic_compare_exchange_weak`
* `atomic_and`
* `atomic_nand`
* `atomic_or`
* `atomic_xor`
* `atomic_max`
* `atomic_min`
* `atomic_umax`
* `atomic_umin`

However, none of those functions and macros actually depend on 8-bit
width and they are needed for all atomic widths (16-bit, 32-bit, 64-bit
etc.). Some targets might not support 8-bit atomics (i.e. BPF, if we
would enable atomic CAS for it).

This change fixes that by removing the `"8"` argument from annotations,
which results in accepting the whole variety of widths.

Fixes rust-lang#106845
Fixes rust-lang#106795

Signed-off-by: Michal Rostecki <[email protected]>
    @vadorovsky
    vadorovsky committed Jan 25, 2023
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    474ea87 View commit details
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