     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75

    use sync::atomic::Ordering;

    #[cfg(test)]
    use stdsimd_test::assert_instr;

    /// Compare and exchange 16 bytes (128 bits) of data atomically.
    ///
    /// This intrinsic corresponds to the `cmpxchg16b` instruction on x86_64
    /// processors. It performs an atomic compare-and-swap, updating the `ptr`
    /// memory location to `val` if the current value in memory equals `old`.
    ///
    /// # Return value
    ///
    /// This function returns the previous value at the memory location. If it is
    /// equal to `old` then the memory was updated to `new`.
    ///
    /// # Memory Orderings
    ///
    /// This atomic operations has the same semantics of memory orderings as
    /// `AtomicUsize::compare_exchange` does, only operating on 16 bytes of memory
    /// instead of just a pointer.
    ///
    /// For more information on memory orderings here see the `compare_exchange`
    /// documentation for other `Atomic*` types in the standard library.
    ///
    /// # Unsafety
    ///
    /// This method is unsafe because it takes a raw pointer and will attempt to
    /// read and possibly write the memory at the pointer. The pointer must also be
    /// aligned on a 16-byte boundary.
    ///
    /// This method also requires the `cmpxchg16b` CPU feature to be available at
    /// runtime to work correctly. If the CPU running the binary does not actually
    /// support `cmpxchg16b` and the program enters an execution path that
    /// eventually would reach this function the behavior is undefined.
    ///
    /// The `success` ordering must also be stronger or equal to `failure`, or this
    /// function call is undefined. See the `Atomic*` documentation's
    /// `compare_exchange` function for more information. When `compare_exchange`
    /// panics, this is undefined behavior. Currently this function aborts the
    /// process with an undefined instruction.
    #[inline]
    #[cfg_attr(test, assert_instr(cmpxchg16b, success = Ordering::SeqCst, failure = Ordering::SeqCst))]
    #[target_feature(enable = "cmpxchg16b")]
    #[cfg(not(stage0))]
    pub unsafe fn cmpxchg16b(
        dst: *mut u128,
        old: u128,
        new: u128,
        success: Ordering,
        failure: Ordering,
    ) -> u128 {
        use intrinsics;
        use sync::atomic::Ordering::*;

        debug_assert!(dst as usize % 16 == 0);

        let (val, _ok) = match (success, failure) {
            (Acquire, Acquire) => intrinsics::atomic_cxchg_acq(dst, old, new),
            (Release, Relaxed) => intrinsics::atomic_cxchg_rel(dst, old, new),
            (AcqRel, Acquire) => intrinsics::atomic_cxchg_acqrel(dst, old, new),
            (Relaxed, Relaxed) => intrinsics::atomic_cxchg_relaxed(dst, old, new),
            (SeqCst, SeqCst) => intrinsics::atomic_cxchg(dst, old, new),
            (Acquire, Relaxed) => intrinsics::atomic_cxchg_acq_failrelaxed(dst, old, new),
            (AcqRel, Relaxed) => intrinsics::atomic_cxchg_acqrel_failrelaxed(dst, old, new),
            (SeqCst, Relaxed) => intrinsics::atomic_cxchg_failrelaxed(dst, old, new),
            (SeqCst, Acquire) => intrinsics::atomic_cxchg_failacq(dst, old, new),

            // The above block is all copied from libcore, and this statement is
            // also copied from libcore except that it's a panic in libcore and we
            // have a little bit more of a lightweight panic here.
            _ => ::coresimd::x86::ud2(),
        };
        val
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)