    const std = @import("std.zig");
    const builtin = @import("builtin");

    pub const Ordering = std.builtin.AtomicOrder;

    pub const Stack = @import("atomic/stack.zig").Stack;
    pub const Queue = @import("atomic/queue.zig").Queue;
    pub const Atomic = @import("atomic/Atomic.zig").Atomic;

    test "std.atomic" {
        _ = @import("atomic/stack.zig");
        _ = @import("atomic/queue.zig");
        _ = @import("atomic/Atomic.zig");
    }

    pub inline fn fence(comptime ordering: Ordering) void {
        switch (ordering) {
            .Acquire, .Release, .AcqRel, .SeqCst => {
                @fence(ordering);
            },
            else => {
                @compileLog(ordering, " only applies to a given memory location");
            },
        }
    }

    pub inline fn compilerFence(comptime ordering: Ordering) void {
        switch (ordering) {
            .Acquire, .Release, .AcqRel, .SeqCst => asm volatile ("" ::: "memory"),
            else => @compileLog(ordering, " only applies to a given memory location"),
        }
    }

    test "fence/compilerFence" {
        inline for (.{ .Acquire, .Release, .AcqRel, .SeqCst }) |ordering| {
            compilerFence(ordering);
            fence(ordering);
        }
    }

    /// Signals to the processor that the caller is inside a busy-wait spin-loop.
    pub inline fn spinLoopHint() void {
        switch (builtin.target.cpu.arch) {
            // No-op instruction that can hint to save (or share with a hardware-thread)

            // pipelining/power resources

            // https://software.intel.com/content/www/us/en/develop/articles/benefitting-power-and-performance-sleep-loops.html

            .i386, .x86_64 => asm volatile ("pause" ::: "memory"),

            // No-op instruction that serves as a hardware-thread resource yield hint.

            // https://stackoverflow.com/a/7588941

            .powerpc64, .powerpc64le => asm volatile ("or 27, 27, 27" ::: "memory"),

            // `isb` appears more reliable for releasing execution resources than `yield`

            // on common aarch64 CPUs.

            // https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8258604

            // https://bugs.mysql.com/bug.php?id=100664

            .aarch64, .aarch64_be, .aarch64_32 => asm volatile ("isb" ::: "memory"),

            // `yield` was introduced in v6k but is also available on v6m.

            // https://www.keil.com/support/man/docs/armasm/armasm_dom1361289926796.htm

            .arm, .armeb, .thumb, .thumbeb => {
                const can_yield = comptime std.Target.arm.featureSetHasAny(builtin.target.cpu.features, .{
                    .has_v6k, .has_v6m,
                });
                if (can_yield) {
                    asm volatile ("yield" ::: "memory");
                } else {
                    asm volatile ("" ::: "memory");
                }
            },
            // Memory barrier to prevent the compiler from optimizing away the spin-loop

            // even if no hint_instruction was provided.

            else => asm volatile ("" ::: "memory"),
        }
    }

    test "spinLoopHint" {
        var i: usize = 10;
        while (i > 0) : (i -= 1) {
            spinLoopHint();
        }
    }

    /// The estimated size of the CPU's cache line when atomically updating memory.
    /// Add this much padding or align to this boundary to avoid atomically-updated
    /// memory from forcing cache invalidations on near, but non-atomic, memory.
    ///
    // https://en.wikipedia.org/wiki/False_sharing

    // https://github.com/golang/go/search?q=CacheLinePadSize

    pub const cache_line = switch (builtin.cpu.arch) {
        // x86_64: Starting from Intel's Sandy Bridge, the spatial prefetcher pulls in pairs of 64-byte cache lines at a time.

        // - https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf

        // - https://github.com/facebook/folly/blob/1b5288e6eea6df074758f877c849b6e73bbb9fbb/folly/lang/Align.h#L107

        //

        // aarch64: Some big.LITTLE ARM archs have "big" cores with 128-byte cache lines:

        // - https://www.mono-project.com/news/2016/09/12/arm64-icache/

        // - https://cpufun.substack.com/p/more-m1-fun-hardware-information

        //

        // powerpc64: PPC has 128-byte cache lines

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_ppc64x.go#L9

        .x86_64, .aarch64, .powerpc64 => 128,

        // These platforms reportedly have 32-byte cache lines

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_arm.go#L7

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips.go#L7

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mipsle.go#L7

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips64x.go#L9

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_riscv64.go#L7

        .arm, .mips, .mips64, .riscv64 => 32,

        // This platform reportedly has 256-byte cache lines

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_s390x.go#L7

        .s390x => 256,

        // Other x86 and WASM platforms have 64-byte cache lines.

        // The rest of the architectures are assumed to be similar.

        // - https://github.com/golang/go/blob/dda2991c2ea0c5914714469c4defc2562a907230/src/internal/cpu/cpu_x86.go#L9

        // - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_wasm.go#L7

        else => 64,
    };