Add spin_loop hint for LoongArch

[heiher]

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[folkertdev]

This function could use cfg_select!:

cfg_select! {
    target_arch = "x86" => { 
        // SAFETY: the `cfg` attr ensures that we only execute this on x86 targets.
        unsafe { crate::arch::x86::_mm_pause() }
    }
    target_arch = "x86_64" => { 
        // SAFETY: the `cfg` attr ensures that we only execute this on x86_64 targets.
        unsafe { crate::arch::x86_64::_mm_pause() }
    }
    target_arch = "riscv32" => crate::arch::riscv32::pause(),
    target_arch = "riscv64" => crate::arch::riscv64::pause(),
    any(target_arch = "aarch64", target_arch = "arm64ec") => { 
        // SAFETY: the `cfg` attr ensures that we only execute this on aarch64 targets.
        unsafe { crate::arch::aarch64::__isb(crate::arch::aarch64::SY) }
    }
    all(target_arch = "arm", target_feature = "v6") => { 
        // SAFETY: the `cfg` attr ensures that we only execute this on arm targets
        // with support for the v6 feature.
        unsafe { crate::arch::arm::__yield() }
    }
    target_arch = "loongarch32" => crate::arch::loongarch32::ibar::<0>(),
    target_arch = "loongarch64" => crate::arch::loongarch64::ibar::<0>(),
    _ => { /* do nothing */ }
}

[heiher]

r? @folkertdev

[joshtriplett]

@bors r+ rollup

[bors]

📌 Commit 0da328b has been approved by joshtriplett

It is now in the queue for this repository.