Macro select_implementation

macro_rules! select_implementation {
    (
        name: $fn_name:ident,
        // Configuration meta for when to use arch-specific implementation that requires hard
        // float ops
        $( use_arch: $use_arch:meta, )?
        // Configuration meta for when to use the arch module regardless of whether softfloats
        // have been requested.
        $( use_arch_required: $use_arch_required:meta, )?
        args: $($arg:ident),+ ,
    ) => { ... };
    (@cfg ; $ex:expr) => { ... };
    (@cfg $provided:meta; $ex:expr) => { ... };
}

Choose between using an arch-specific implementation and the function body. Returns directly if the arch implementation is used, otherwise continue with the rest of the function.

Specify a use_arch meta field if an architecture-specific implementation is provided. These live in the math::arch::some_target_arch module.

Specify a use_arch_required meta field if something architecture-specific must be used regardless of feature configuration (force-soft-floats).

The passed meta options do not need to account for the arch target feature.