//! Replaces 128-bit operators with lang item calls where necessary

use cranelift_codegen::ir::ArgumentPurpose;

use crate::prelude::*;

pub(crate) fn maybe_codegen<'tcx>(
    fx: &mut FunctionCx<'_, '_, 'tcx>,
    bin_op: BinOp,
    lhs: CValue<'tcx>,
    rhs: CValue<'tcx>,
) -> Option<CValue<'tcx>> {
    if lhs.layout().ty != fx.tcx.types.u128
        && lhs.layout().ty != fx.tcx.types.i128
        && rhs.layout().ty != fx.tcx.types.u128
        && rhs.layout().ty != fx.tcx.types.i128
    {
        return None;
    }

    let is_signed = type_sign(lhs.layout().ty);

    match bin_op {
        BinOp::BitAnd | BinOp::BitOr | BinOp::BitXor => None,
        BinOp::Add | BinOp::AddUnchecked | BinOp::Sub | BinOp::SubUnchecked => None,
        BinOp::Mul | BinOp::MulUnchecked => {
            let args = [lhs.load_scalar(fx), rhs.load_scalar(fx)];
            let ret_val = fx.lib_call(
                "__multi3",
                vec![AbiParam::new(types::I128), AbiParam::new(types::I128)],
                vec![AbiParam::new(types::I128)],
                &args,
            )[0];
            Some(CValue::by_val(
                ret_val,
                fx.layout_of(if is_signed { fx.tcx.types.i128 } else { fx.tcx.types.u128 }),
            ))
        }
        BinOp::Offset => unreachable!("offset should only be used on pointers, not 128bit ints"),
        BinOp::Div | BinOp::Rem => {
            let name = match (bin_op, is_signed) {
                (BinOp::Div, false) => "__udivti3",
                (BinOp::Div, true) => "__divti3",
                (BinOp::Rem, false) => "__umodti3",
                (BinOp::Rem, true) => "__modti3",
                _ => unreachable!(),
            };
            if fx.tcx.sess.target.is_like_windows {
                let args = [lhs.load_scalar(fx), rhs.load_scalar(fx)];
                let ret = fx.lib_call(
                    name,
                    vec![AbiParam::new(types::I128), AbiParam::new(types::I128)],
                    vec![AbiParam::new(types::I64X2)],
                    &args,
                )[0];
                // FIXME(bytecodealliance/wasmtime#6104) use bitcast instead of store to get from i64x2 to i128
                let ret_place = CPlace::new_stack_slot(fx, lhs.layout());
                ret_place.to_ptr().store(fx, ret, MemFlags::trusted());
                Some(ret_place.to_cvalue(fx))
            } else {
                let args = [lhs.load_scalar(fx), rhs.load_scalar(fx)];
                let ret_val = fx.lib_call(
                    name,
                    vec![AbiParam::new(types::I128), AbiParam::new(types::I128)],
                    vec![AbiParam::new(types::I128)],
                    &args,
                )[0];
                Some(CValue::by_val(ret_val, lhs.layout()))
            }
        }
        BinOp::Lt | BinOp::Le | BinOp::Eq | BinOp::Ge | BinOp::Gt | BinOp::Ne => None,
        BinOp::Shl | BinOp::ShlUnchecked | BinOp::Shr | BinOp::ShrUnchecked => None,
    }
}

pub(crate) fn maybe_codegen_checked<'tcx>(
    fx: &mut FunctionCx<'_, '_, 'tcx>,
    bin_op: BinOp,
    lhs: CValue<'tcx>,
    rhs: CValue<'tcx>,
) -> Option<CValue<'tcx>> {
    if lhs.layout().ty != fx.tcx.types.u128
        && lhs.layout().ty != fx.tcx.types.i128
        && rhs.layout().ty != fx.tcx.types.u128
        && rhs.layout().ty != fx.tcx.types.i128
    {
        return None;
    }

    let is_signed = type_sign(lhs.layout().ty);

    match bin_op {
        BinOp::BitAnd | BinOp::BitOr | BinOp::BitXor => unreachable!(),
        BinOp::Mul if is_signed => {
            let out_ty = Ty::new_tup(fx.tcx, &[lhs.layout().ty, fx.tcx.types.bool]);
            let oflow = CPlace::new_stack_slot(fx, fx.layout_of(fx.tcx.types.i32));
            let lhs = lhs.load_scalar(fx);
            let rhs = rhs.load_scalar(fx);
            let oflow_ptr = oflow.to_ptr().get_addr(fx);
            let res = fx.lib_call_unadjusted(
                "__muloti4",
                vec![
                    AbiParam::new(types::I128),
                    AbiParam::new(types::I128),
                    AbiParam::new(fx.pointer_type),
                ],
                vec![AbiParam::new(types::I128)],
                &[lhs, rhs, oflow_ptr],
            )[0];
            let oflow = oflow.to_cvalue(fx).load_scalar(fx);
            let oflow = fx.bcx.ins().ireduce(types::I8, oflow);
            Some(CValue::by_val_pair(res, oflow, fx.layout_of(out_ty)))
        }
        BinOp::Add | BinOp::Sub | BinOp::Mul => {
            let out_ty = Ty::new_tup(fx.tcx, &[lhs.layout().ty, fx.tcx.types.bool]);
            let out_place = CPlace::new_stack_slot(fx, fx.layout_of(out_ty));
            let param_types = vec![
                AbiParam::special(fx.pointer_type, ArgumentPurpose::StructReturn),
                AbiParam::new(types::I128),
                AbiParam::new(types::I128),
            ];
            let args = [out_place.to_ptr().get_addr(fx), lhs.load_scalar(fx), rhs.load_scalar(fx)];
            let name = match (bin_op, is_signed) {
                (BinOp::Add, false) => "__rust_u128_addo",
                (BinOp::Add, true) => "__rust_i128_addo",
                (BinOp::Sub, false) => "__rust_u128_subo",
                (BinOp::Sub, true) => "__rust_i128_subo",
                (BinOp::Mul, false) => "__rust_u128_mulo",
                _ => unreachable!(),
            };
            fx.lib_call(name, param_types, vec![], &args);
            Some(out_place.to_cvalue(fx))
        }
        BinOp::AddUnchecked | BinOp::SubUnchecked | BinOp::MulUnchecked => unreachable!(),
        BinOp::Offset => unreachable!("offset should only be used on pointers, not 128bit ints"),
        BinOp::Div | BinOp::Rem => unreachable!(),
        BinOp::Lt | BinOp::Le | BinOp::Eq | BinOp::Ge | BinOp::Gt | BinOp::Ne => unreachable!(),
        BinOp::Shl | BinOp::ShlUnchecked | BinOp::Shr | BinOp::ShrUnchecked => unreachable!(),
    }
}