rust/src/codegen_i128.rs

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

use crate::prelude::*;

pub fn maybe_codegen<'a, 'tcx>(
    fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
    bin_op: BinOp,
    checked: bool,
    is_signed: bool,
    lhs: CValue<'tcx>,
    rhs: CValue<'tcx>,
    out_ty: Ty<'tcx>,
) -> Option<CValue<'tcx>> {
    if lhs.layout().ty != fx.tcx.types.u128 && lhs.layout().ty != fx.tcx.types.i128 {
        return None;
    }

    let lhs_val = lhs.load_scalar(fx);
    let rhs_val = rhs.load_scalar(fx);

    match bin_op {
        BinOp::BitAnd | BinOp::BitOr | BinOp::BitXor => {
            assert!(!checked);
            return None;
        }
        BinOp::Add | BinOp::Sub => {
            return None; // FIXME implement checked versions
        }
        BinOp::Offset => unreachable!("offset should only be used on pointers, not 128bit ints"),
        BinOp::Mul => {
            let res = if checked {
                if is_signed {
                    fx.easy_call("__rust_i128_mulo", &[lhs, rhs], out_ty)
                } else {
                    fx.easy_call("__rust_u128_mulo", &[lhs, rhs], out_ty)
                }
            } else {
                let val_ty = if is_signed { fx.tcx.types.i128 } else { fx.tcx.types.u128 };
                fx.easy_call("__multi3", &[lhs, rhs], val_ty)
            };
            return Some(res);
        }
        BinOp::Div => {
            assert!(!checked);
            if is_signed {
                Some(fx.easy_call("__divti3", &[lhs, rhs], fx.tcx.types.i128))
            } else {
                Some(fx.easy_call("__udivti3", &[lhs, rhs], fx.tcx.types.u128))
            }
        }
        BinOp::Rem => {
            assert!(!checked);
            if is_signed {
                Some(fx.easy_call("__modti3", &[lhs, rhs], fx.tcx.types.i128))
            } else {
                Some(fx.easy_call("__umodti3", &[lhs, rhs], fx.tcx.types.u128))
            }
        }
        BinOp::Lt | BinOp::Le | BinOp::Eq | BinOp::Ge | BinOp::Gt | BinOp::Ne => {
            assert!(!checked);
            let (lhs_lsb, lhs_msb) = fx.bcx.ins().isplit(lhs_val);
            let (rhs_lsb, rhs_msb) = fx.bcx.ins().isplit(rhs_val);

            let res = match bin_op {
                BinOp::Eq => {
                    let lsb_eq = fx.bcx.ins().icmp(IntCC::Equal, lhs_lsb, rhs_lsb);
                    let msb_eq = fx.bcx.ins().icmp(IntCC::Equal, lhs_msb, rhs_msb);
                    fx.bcx.ins().band(lsb_eq, msb_eq)
                }
                BinOp::Ne => {
                    let lsb_ne = fx.bcx.ins().icmp(IntCC::NotEqual, lhs_lsb, rhs_lsb);
                    let msb_ne = fx.bcx.ins().icmp(IntCC::NotEqual, lhs_msb, rhs_msb);
                    fx.bcx.ins().bor(lsb_ne, msb_ne)
                }
                _ => {
                    // if msb_eq {
                    //     lhs_cc
                    // } else {
                    //     msb_cc
                    // }
                    let cc = match (bin_op, is_signed) {
                        (BinOp::Ge, false) => IntCC::UnsignedGreaterThanOrEqual,
                        (BinOp::Gt, false) => IntCC::UnsignedGreaterThan,
                        (BinOp::Lt, false) => IntCC::UnsignedLessThan,
                        (BinOp::Le, false) => IntCC::UnsignedLessThanOrEqual,

                        (BinOp::Ge, true) => IntCC::SignedGreaterThanOrEqual,
                        (BinOp::Gt, true) => IntCC::SignedGreaterThan,
                        (BinOp::Lt, true) => IntCC::SignedLessThan,
                        (BinOp::Le, true) => IntCC::SignedLessThanOrEqual,
                        _ => unreachable!(),
                    };

                    let msb_eq = fx.bcx.ins().icmp(IntCC::Equal, lhs_msb, rhs_msb);
                    let lsb_cc = fx.bcx.ins().icmp(cc, lhs_lsb, rhs_lsb);
                    let msb_cc = fx.bcx.ins().icmp(cc, lhs_msb, rhs_msb);

                    fx.bcx.ins().select(msb_eq, lsb_cc, msb_cc)
                }
            };

            let res = fx.bcx.ins().bint(types::I8, res);
            let res = CValue::by_val(res, fx.layout_of(fx.tcx.types.bool));
            return Some(res);
        }
        BinOp::Shl | BinOp::Shr => {
            let is_overflow = if checked {
                // rhs >= 128

                // FIXME support non 128bit rhs
                /*let (rhs_lsb, rhs_msb) = fx.bcx.ins().isplit(rhs_val);
                let rhs_msb_gt_0 = fx.bcx.ins().icmp_imm(IntCC::NotEqual, rhs_msb, 0);
                let rhs_lsb_ge_128 = fx.bcx.ins().icmp_imm(IntCC::SignedGreaterThan, rhs_lsb, 127);
                let is_overflow = fx.bcx.ins().bor(rhs_msb_gt_0, rhs_lsb_ge_128);*/
                let is_overflow = fx.bcx.ins().bconst(types::B1, false);

                Some(fx.bcx.ins().bint(types::I8, is_overflow))
            } else {
                None
            };

            // Optimize `val >> 64`, because compiler_builtins uses it to deconstruct an 128bit
            // integer into its lsb and msb.
            // https://github.com/rust-lang-nursery/compiler-builtins/blob/79a6a1603d5672cbb9187ff41ff4d9b5048ac1cb/src/int/mod.rs#L217
            if let Some(64) = resolve_value_imm(fx.bcx.func, rhs_val) {
                let (lhs_lsb, lhs_msb) = fx.bcx.ins().isplit(lhs_val);
                let all_zeros = fx.bcx.ins().iconst(types::I64, 0);
                let val = match (bin_op, is_signed) {
                    (BinOp::Shr, false) => {
                        let val = fx.bcx.ins().iconcat(lhs_msb, all_zeros);
                        Some(CValue::by_val(val, fx.layout_of(fx.tcx.types.u128)))
                    }
                    (BinOp::Shr, true) => {
                        let sign = fx.bcx.ins().icmp_imm(IntCC::SignedLessThan, lhs_msb, 0);
                        let all_ones = fx.bcx.ins().iconst(types::I64, u64::max_value() as i64);
                        let all_sign_bits = fx.bcx.ins().select(sign, all_zeros, all_ones);

                        let val = fx.bcx.ins().iconcat(lhs_msb, all_sign_bits);
                        Some(CValue::by_val(val, fx.layout_of(fx.tcx.types.i128)))
                    }
                    (BinOp::Shl, _) => {
                        let val_ty = if is_signed { fx.tcx.types.i128 } else { fx.tcx.types.u128 };
                        let val = fx.bcx.ins().iconcat(all_zeros, lhs_lsb);
                        Some(CValue::by_val(val, fx.layout_of(val_ty)))
                    }
                    _ => None
                };
                if let Some(val) = val {
                    if let Some(is_overflow) = is_overflow {
                        let val = val.load_scalar(fx);
                        return Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)))
                    } else {
                        return Some(val);
                    }
                }
            }

            let truncated_rhs = clif_intcast(fx, rhs_val, types::I32, false);
            let truncated_rhs = CValue::by_val(truncated_rhs, fx.layout_of(fx.tcx.types.u32));
            let val = match (bin_op, is_signed) {
                (BinOp::Shl, false) => {
                    fx.easy_call("__ashlti3", &[lhs, truncated_rhs], fx.tcx.types.u128)
                }
                (BinOp::Shl, true) => {
                    fx.easy_call("__ashlti3", &[lhs, truncated_rhs], fx.tcx.types.i128)
                }
                (BinOp::Shr, false) => {
                    fx.easy_call("__lshrti3", &[lhs, truncated_rhs], fx.tcx.types.u128)
                }
                (BinOp::Shr, true) => {
                    fx.easy_call("__ashrti3", &[lhs, truncated_rhs], fx.tcx.types.i128)
                }
                (_, _) => unreachable!(),
            };
            if let Some(is_overflow) = is_overflow {
                let val = val.load_scalar(fx);
                Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)))
            } else {
                Some(val)
            }
        }
    }
}