Macro impl_atomic_primitive 

macro impl_atomic_primitive {
    (
        @impl [$($T:ident)?] $Primitive:ty as $Storage:ident<$Operand:ty>,
        $cfg:meta
    ) => { ... },
    (
        [$($T:ident)?] $Primitive:ty as $Storage:ident<$Operand:ty>,
        size($size:literal)
    ) => { ... },
    (
        [$($T:ident)?] $Primitive:ty as $Storage:ident<$Operand:ty>,
        size($size:literal),
        doc
    ) => { ... },
}