// SPDX-License-Identifier: LGPL-3.0-or-later
// See Notices.txt for copyright information
use fayalite::prelude::*;

#[hdl]
pub enum FlagsMode {
    PowerISA(PRegFlagsPowerISA),
    X86(PRegFlagsX86),
}

#[hdl(cmp_eq)]
pub struct PRegFlagsPowerISA {}

impl PRegFlagsPowerISA {
    pub fn xer_ca(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ca_x86_cf
    }
    pub fn xer_ca32(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ca32_x86_af
    }
    pub fn xer_ov(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ov_x86_of
    }
    pub fn xer_ov32(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ov32_x86_df
    }
    /// both `CR<N>.SO` and `XER.SO` since instructions that write to both always write the same value
    pub fn so(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_so
    }
    pub fn cr_lt(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_lt_x86_sf
    }
    pub fn cr_gt(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_gt_x86_pf
    }
    pub fn cr_eq(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_eq_x86_zf
    }
    #[hdl]
    pub fn clear_unused(flags: impl ToExpr<Type = PRegFlags>) {
        // list all flags explicitly so we don't miss handling any new flags
        #[hdl]
        let PRegFlags {
            pwr_ca_x86_cf: _,
            pwr_ca32_x86_af: _,
            pwr_ov_x86_of: _,
            pwr_ov32_x86_df: _,
            pwr_cr_lt_x86_sf: _,
            pwr_cr_gt_x86_pf: _,
            pwr_cr_eq_x86_zf: _,
            pwr_so: _,
        } = flags;
    }
}

#[hdl(cmp_eq)]
pub struct PRegFlagsX86 {}

impl PRegFlagsX86 {
    pub fn cf(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ca_x86_cf
    }
    pub fn zf(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_eq_x86_zf
    }
    pub fn sf(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_lt_x86_sf
    }
    pub fn of(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ov_x86_of
    }
    pub fn af(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ca32_x86_af
    }
    pub fn pf(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_cr_gt_x86_pf
    }
    pub fn df(flags: impl ToExpr<Type = PRegFlags>) -> Expr<Bool> {
        flags.to_expr().pwr_ov32_x86_df
    }
    #[hdl]
    pub fn clear_unused(flags: impl ToExpr<Type = PRegFlags>) {
        // list all flags explicitly so we don't miss handling any new flags
        #[hdl]
        let PRegFlags {
            pwr_ca_x86_cf: _,
            pwr_ca32_x86_af: _,
            pwr_ov_x86_of: _,
            pwr_ov32_x86_df: _,
            pwr_cr_lt_x86_sf: _,
            pwr_cr_gt_x86_pf: _,
            pwr_cr_eq_x86_zf: _,
            pwr_so: unused1,
        } = flags;
        connect(unused1, false);
    }
}

#[hdl(cmp_eq)]
/// this is *not* the same as any particular ISA's flags register,
/// on PowerISA it is a combination of some bits from XER with a single 4-bit CR field.
///
/// Accessor functions depend on the ISA:
///
/// * PowerISA: [`struct@PRegFlagsPowerISA`]
/// * x86: [`struct@PRegFlagsX86`]
pub struct PRegFlags {
    pwr_ca_x86_cf: Bool,
    pwr_ca32_x86_af: Bool,
    pwr_ov_x86_of: Bool,
    pwr_ov32_x86_df: Bool,
    pwr_cr_lt_x86_sf: Bool,
    pwr_cr_gt_x86_pf: Bool,
    pwr_cr_eq_x86_zf: Bool,
    pwr_so: Bool,
}

impl PRegFlags {
    /// if trying to set all fields individually, prefer using the individual accessor
    /// functions and [`PRegFlagsPowerISA::clear_unused()`]/[`PRegFlagsX86::clear_unused()`]/etc.
    #[hdl]
    pub fn zeroed() -> Expr<PRegFlags> {
        #[hdl]
        PRegFlags {
            pwr_ca_x86_cf: false,
            pwr_ca32_x86_af: false,
            pwr_ov_x86_of: false,
            pwr_ov32_x86_df: false,
            pwr_cr_lt_x86_sf: false,
            pwr_cr_gt_x86_pf: false,
            pwr_cr_eq_x86_zf: false,
            pwr_so: false,
        }
    }
}

#[hdl(cmp_eq)]
/// Unit output register's value -- a combination of an integer/fp register
/// and flags register and CR field.
///
/// Register Renaming will independently rename the ISA-level integer/fp
/// register, flags, and CR field portions.
pub struct PRegValue {
    pub int_fp: UInt<64>,
    pub flags: PRegFlags,
}

impl PRegValue {
    #[hdl]
    pub fn zeroed() -> Expr<Self> {
        #[hdl]
        PRegValue {
            int_fp: 0u64,
            flags: PRegFlags::zeroed(),
        }
    }
}