use crate::abi::call::{ArgAbi, FnAbi, PassMode, Reg, Size, Uniform};
use crate::abi::{HasDataLayout, TyAbiInterface};

fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
    if ret.layout.is_aggregate() && ret.layout.size.bits() > 64 {
        ret.make_indirect();
    } else {
        // FIXME: this is wrong! Need to decide which ABI we really want here.
        ret.make_direct_deprecated();
    }
}

fn classify_arg<Ty>(arg: &mut ArgAbi<'_, Ty>) {
    if arg.layout.is_aggregate() && arg.layout.size.bits() > 64 {
        arg.make_indirect();
    } else {
        // FIXME: this is wrong! Need to decide which ABI we really want here.
        arg.make_direct_deprecated();
    }
}

fn classify_arg_kernel<'a, Ty, C>(_cx: &C, arg: &mut ArgAbi<'a, Ty>)
where
    Ty: TyAbiInterface<'a, C> + Copy,
    C: HasDataLayout,
{
    if matches!(arg.mode, PassMode::Pair(..)) && (arg.layout.is_adt() || arg.layout.is_tuple()) {
        let align_bytes = arg.layout.align.abi.bytes();

        let unit = match align_bytes {
            1 => Reg::i8(),
            2 => Reg::i16(),
            4 => Reg::i32(),
            8 => Reg::i64(),
            16 => Reg::i128(),
            _ => unreachable!("Align is given as power of 2 no larger than 16 bytes"),
        };
        arg.cast_to(Uniform { unit, total: Size::from_bytes(2 * align_bytes) });
    } else {
        // FIXME: find a better way to do this. See https://github.com/rust-lang/rust/issues/117271.
        arg.make_direct_deprecated();
    }
}

pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>) {
    if !fn_abi.ret.is_ignore() {
        classify_ret(&mut fn_abi.ret);
    }

    for arg in fn_abi.args.iter_mut() {
        if arg.is_ignore() {
            continue;
        }
        classify_arg(arg);
    }
}

pub fn compute_ptx_kernel_abi_info<'a, Ty, C>(cx: &C, fn_abi: &mut FnAbi<'a, Ty>)
where
    Ty: TyAbiInterface<'a, C> + Copy,
    C: HasDataLayout,
{
    if !fn_abi.ret.layout.is_unit() && !fn_abi.ret.layout.is_never() {
        panic!("Kernels should not return anything other than () or !");
    }

    for arg in fn_abi.args.iter_mut() {
        if arg.is_ignore() {
            continue;
        }
        classify_arg_kernel(cx, arg);
    }
}