m68k 0.10.14

//! 68060 instruction timing: superscalar classification and pOEP cycle costs.
//!
//! The 68060 executes most integer instructions in one clock in the primary
//! operand-execution pipeline (pOEP); a restricted subset may dispatch to the
//! secondary pipeline (sOEP) in the same clock. MC68060UM Chapter 10 defines
//! the dispatch algorithm (Table 10-1) and classifies every instruction
//! (Tables 10-2/10-3); this module transcribes that classification as a pure
//! function of the opcode word, accelerated by a build-once 64K table.
//!
//! Costs returned here are pOEP occupancy assuming zero-wait operand access:
//! all memory latency is billed by the host bus at access time, so a cheap
//! count here never double-bills a bus access. The classification is
//! deliberately pessimistic where the manual's rules are finer than an
//! opcode-word decode can see (pessimism under-pairs; it never over-pairs).
//! The per-instruction constants are estimates for pipeline effects that the
//! opcode classification alone cannot derive.

use super::cpu::CpuCore;
use std::sync::OnceLock;

/// UM Tables 10-2/10-3 dispatch classes.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum OepClass {
    /// May execute in either pipeline (the common 1-cycle instructions).
    PoepSoep = 0,
    /// Occupies the pOEP; nothing dispatches to the sOEP that cycle.
    PoepOnly = 1,
    /// Multi-cycle in the pOEP; an sOEP partner may join the final cycle
    /// (MOVEM is the canonical case).
    PoepUntilLast = 2,
    /// Must start in the pOEP but a pOEP|sOEP successor may still pair.
    PoepButAllowsSoep = 3,
}

/// Packed per-opcode timing entry: class(2) | cycles(5) | flags(9).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Info060(pub u16);

const CLASS_SHIFT: u16 = 0;
const CYCLES_SHIFT: u16 = 2;
const CYCLES_MASK: u16 = 0x1F;

/// Bcc/BRA/BSR: costed via the branch path (branch cache once it lands).
pub const F_BRANCH: u16 = 1 << 7;
/// DBcc: a branch with its own loop-mode cost.
pub const F_DBCC: u16 = 1 << 8;
/// Cost varies with data (divides, MOVEM, ...): derive from the handler's
/// raw 68000 count instead of the packed cycles field.
pub const F_VARIABLE: u16 = 1 << 9;
/// Instruction defines the CCR (partner CCR-consumers cannot pair behind it).
pub const F_DEFINES_CCR: u16 = 1 << 10;
/// Instruction consumes the CCR/X late (Scc, ADDX-style, DBcc).
pub const F_USES_CCR_LATE: u16 = 1 << 11;
/// Memory-indirect or indexed EA: +1 pOEP cycle, and never an sOEP candidate.
pub const F_EA_INDEXED: u16 = 1 << 12;
/// Not yet classified from the UM tables: pessimistic pOEP-only + raw fallback.
pub const F_UNCLASSIFIED: u16 = 1 << 13;
/// Instruction reads a memory operand.
pub const F_READS_MEM: u16 = 1 << 14;
/// Instruction writes a memory operand.
pub const F_WRITES_MEM: u16 = 1 << 15;

impl Info060 {
    const fn new(class: OepClass, cycles: u16, flags: u16) -> Self {
        Self((class as u16) << CLASS_SHIFT | (cycles & CYCLES_MASK) << CYCLES_SHIFT | flags)
    }

    /// Return the instruction's operand-execution-pipeline dispatch class.
    pub fn class(self) -> OepClass {
        match (self.0 >> CLASS_SHIFT) & 3 {
            0 => OepClass::PoepSoep,
            1 => OepClass::PoepOnly,
            2 => OepClass::PoepUntilLast,
            _ => OepClass::PoepButAllowsSoep,
        }
    }

    /// Return the packed primary-pipeline occupancy in clocks.
    pub fn cycles(self) -> i32 {
        i32::from((self.0 >> CYCLES_SHIFT) & CYCLES_MASK)
    }

    /// Return whether the packed entry contains `flag`.
    pub fn has(self, flag: u16) -> bool {
        self.0 & flag != 0
    }
}

// Pipeline-effect estimates kept separate from the opcode classification.
/// Taken Bcc/BRA/BSR without branch-cache help: pipeline refill.
pub const CYC_060_BRANCH_TAKEN: i32 = 7;
/// Not-taken conditional branch.
pub const CYC_060_BRANCH_NOT_TAKEN: i32 = 1;
/// DBcc that loops (counter not expired, condition false).
pub const CYC_060_DBCC_TAKEN: i32 = 2;
/// DBcc that falls through.
pub const CYC_060_DBCC_EXPIRED: i32 = 3;
/// Floor for non-branch flow changes (JMP/JSR/RTS/RTE...): refill cost.
pub const CYC_060_FLOW_MIN: i32 = 5;

/// Mispredicted (or unpredicted-taken) branch with the branch cache on.
pub const CYC_060_MISPREDICT: i32 = 7;

/// The 68060's 256-entry branch cache, modeled as a direct-mapped table of
/// branch PCs with 2-bit saturating taken counters. A hit that predicts a
/// taken branch correctly folds it to zero cycles; misses predict not-taken
/// and allocate on a taken execution. Entries record the privilege mode at
/// allocation so CACR.CUBC can clear only user entries. The cache changes
/// cycle counts and cycle counts change chipset interleaving, so it is
/// serialized with the rest of the CPU.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct BranchCache060 {
    /// Full branch PC per slot (the tag).
    tags: Vec<u32>,
    /// Bit 2 = valid, bit 3 = allocated in user mode, bits 1:0 = 2-bit
    /// saturating taken counter (predict taken when >= 2).
    state: Vec<u8>,
}

const BC_VALID: u8 = 1 << 2;
const BC_USER: u8 = 1 << 3;
const BC_COUNTER: u8 = 0x03;

impl Default for BranchCache060 {
    fn default() -> Self {
        Self {
            tags: vec![0; 256],
            state: vec![0; 256],
        }
    }
}

impl BranchCache060 {
    #[inline]
    fn slot(pc: u32) -> usize {
        ((pc >> 1) & 0xFF) as usize
    }

    /// Invalidate every branch-cache entry (CACR.CABC).
    pub fn clear_all(&mut self) {
        self.state.iter_mut().for_each(|s| *s = 0);
    }

    /// CACR.CUBC: clear only entries allocated in user mode.
    pub fn clear_user(&mut self) {
        for s in self.state.iter_mut() {
            if *s & BC_USER != 0 {
                *s = 0;
            }
        }
    }

    /// Prediction for the branch at `pc`: Some(taken?) on a hit, None on a
    /// miss (which predicts not-taken).
    fn predict(&self, pc: u32) -> Option<bool> {
        let i = Self::slot(pc);
        if self.state[i] & BC_VALID != 0 && self.tags[i] == pc {
            Some(self.state[i] & BC_COUNTER >= 2)
        } else {
            None
        }
    }

    /// Record an executed branch: allocate on a taken miss (weakly taken),
    /// step the counter on a hit. Not-taken misses do not allocate.
    fn update(&mut self, pc: u32, taken: bool, user: bool) {
        let i = Self::slot(pc);
        let hit = self.state[i] & BC_VALID != 0 && self.tags[i] == pc;
        if hit {
            let mut counter = self.state[i] & BC_COUNTER;
            counter = if taken {
                (counter + 1).min(3)
            } else {
                counter.saturating_sub(1)
            };
            self.state[i] = (self.state[i] & !BC_COUNTER) | counter;
        } else if taken {
            self.tags[i] = pc;
            self.state[i] = BC_VALID | if user { BC_USER } else { 0 } | 2;
        }
    }
}

/// An instruction resident in the pOEP with its sOEP slot still open,
/// waiting for the next instruction to try the dispatch test.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct PendingHead060 {
    /// Registers the head writes (D0-D7 = bits 0-7, A0-A7 = 8-15).
    pub def_mask: u16,
    /// The head defines the CCR (late CCR consumers cannot pair behind it).
    pub defines_ccr: bool,
    /// The head has a memory operand (v1: at most one per pair).
    pub accessed_mem: bool,
    /// The head's opcode fetch hit the instruction cache.
    pub head_cached: bool,
}

/// 68060 pipeline timing state carried on the CPU (serialized: it changes
/// future cycle counts, and cycle counts change chipset interleaving).
#[derive(Debug, Clone, Default, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Oep060Timing {
    /// Direct-mapped 68060 branch-prediction cache.
    pub branch_cache: BranchCache060,
    /// Retrospective pairing: the previous instruction, when it left an
    /// sOEP slot open. None after any pipeline break.
    pub pending_head: Option<PendingHead060>,
}

/// The 68060 rule of thumb for costs not in the table: a 4-clock 68000
/// register operation is 1 clock on the 060. Never reuse the 020+ scaling
/// formula here - its `.max(2)` floor would destroy 1-cycle costs.
#[inline]
fn fallback_cycles(raw: i32) -> i32 {
    (raw / 4).max(1)
}

/// Standard-EA helper: flags contributed by an effective-address field.
/// `read`/`write` say whether the instruction reads/writes that operand.
const fn ea_flags(mode: u16, reg: u16, read: bool, write: bool) -> u16 {
    let mut flags = 0;
    let is_mem = mode >= 2 && !(mode == 7 && reg == 4); // not Rn, not #imm
    if is_mem {
        if read {
            flags |= F_READS_MEM;
        }
        if write {
            flags |= F_WRITES_MEM;
        }
    }
    // Brief/full-format indexed and memory-indirect modes: (d8,An,Xn) and
    // (d8,PC,Xn) families. The opcode word cannot distinguish brief from
    // full extension words, so both are treated as indexed (pessimistic).
    if mode == 6 || (mode == 7 && reg == 3) {
        flags |= F_EA_INDEXED;
    }
    flags
}

/// One-cycle pOEP|sOEP ALU entry with standard EA flags.
const fn alu(mode: u16, reg: u16, read: bool, write: bool) -> Info060 {
    Info060::new(
        OepClass::PoepSoep,
        1,
        F_DEFINES_CCR | ea_flags(mode, reg, read, write),
    )
}

/// Classify one opcode word. Arranged in the same group order as
/// `decode::dispatch_instruction` so the two files can be reviewed side by
/// side. Unknown encodings return a pessimistic unclassified entry; illegal
/// encodings never reach the cost path (they trap).
pub fn classify_060_opcode(op: u16) -> Info060 {
    let group = op >> 12;
    let mode = (op >> 3) & 7;
    let reg = op & 7;
    let unclassified = Info060::new(OepClass::PoepOnly, 1, F_UNCLASSIFIED | F_VARIABLE);

    match group {
        0x0 => {
            if op & 0x0100 != 0 || (op & 0x0F00) == 0x0800 {
                // Bit ops BTST/BCHG/BCLR/BSET (dynamic and static #), MOVEP.
                // UM Table 10-2: bit operations are pOEP-only.
                Info060::new(
                    OepClass::PoepOnly,
                    1,
                    F_DEFINES_CCR | ea_flags(mode, reg, true, op & 0x00C0 != 0),
                )
            } else if (op & 0x0FC0) == 0x00C0 || (op & 0x09C0) == 0x08C0 {
                // CMP2/CHK2/CAS/CAS2/MOVES: pOEP-only, data-dependent.
                unclassified
            } else {
                // ORI/ANDI/SUBI/ADDI/EORI/CMPI #imm,<ea> (1 cycle, pOEP|sOEP);
                // the to-CCR/to-SR forms are privileged/serializing.
                if mode == 7 && reg == 4 {
                    Info060::new(OepClass::PoepOnly, 1, F_VARIABLE) // to CCR/SR
                } else {
                    alu(mode, reg, true, (op & 0x0F00) != 0x0C00) // CMPI never writes
                }
            }
        }
        // MOVE.B/L/W and MOVEA: 1 cycle, pOEP|sOEP. Source EA read plus
        // destination EA write; indexed penalty from either side.
        0x1..=0x3 => {
            let dst_mode = (op >> 6) & 7;
            let dst_reg = (op >> 9) & 7;
            Info060::new(
                OepClass::PoepSoep,
                1,
                F_DEFINES_CCR
                    | ea_flags(mode, reg, true, false)
                    | ea_flags(dst_mode, dst_reg, false, true),
            )
        }
        0x4 => {
            match op & 0x0FC0 {
                // MOVE from SR / from CCR: serializing.
                0x00C0 | 0x02C0 => Info060::new(OepClass::PoepOnly, 1, F_VARIABLE),
                // MOVE to CCR / to SR.
                0x04C0 | 0x06C0 => Info060::new(OepClass::PoepOnly, 1, F_VARIABLE),
                _ => {
                    if (op & 0x0B80) == 0x0880 && mode != 0 {
                        // MOVEM: pOEP-until-last, one cycle per register plus
                        // setup - data-dependent, so raw fallback.
                        Info060::new(
                            OepClass::PoepUntilLast,
                            2,
                            F_VARIABLE | F_READS_MEM | F_WRITES_MEM,
                        )
                    } else if (op & 0x0FC0) == 0x0AC0 {
                        // TAS: locked RMW, pOEP-only.
                        Info060::new(
                            OepClass::PoepOnly,
                            2,
                            F_DEFINES_CCR | F_READS_MEM | F_WRITES_MEM,
                        )
                    } else if (op & 0x0F80) == 0x0C00 {
                        // MULL/DIVL (4C00/4C40): pOEP-only, data-dependent.
                        Info060::new(OepClass::PoepOnly, 2, F_DEFINES_CCR | F_VARIABLE)
                    } else if (op & 0x0FF8) == 0x0840 {
                        // SWAP
                        alu(0, 0, false, false)
                    } else if (op & 0x0E00) == 0x0800 && (op & 0x00C0) != 0x0040 {
                        // NBCD/EXT/EXTB (CLR handled below); EXT is pOEP|sOEP.
                        alu(mode, reg, true, true)
                    } else if (op & 0x0F00) == 0x0200
                        || (op & 0x0F00) == 0x0000
                        || (op & 0x0F00) == 0x0400
                        || (op & 0x0F00) == 0x0600
                    {
                        // NEGX/CLR/NEG/NOT <ea>: 1 cycle pOEP|sOEP.
                        alu(mode, reg, true, true)
                    } else if (op & 0x01C0) == 0x01C0 {
                        // LEA: 1 cycle, pOEP|sOEP (indexed forms pay +1).
                        Info060::new(OepClass::PoepSoep, 1, ea_flags(mode, reg, false, false))
                    } else if (op & 0x01C0) == 0x0180 {
                        // CHK: pOEP-only.
                        Info060::new(OepClass::PoepOnly, 2, F_VARIABLE)
                    } else {
                        // JSR/JMP/RTS/RTE/RTR/LINK/UNLK/PEA/TRAP/STOP/MOVEC/
                        // MOVE USP/TST... TST is common enough to special-case.
                        if (op & 0x0F00) == 0x0A00 {
                            // TST <ea>
                            alu(mode, reg, true, false)
                        } else {
                            // Control-flow and supervisor ops: pOEP-only; the
                            // flow-change floor in cycles_060 covers refills.
                            Info060::new(OepClass::PoepOnly, 1, F_VARIABLE)
                        }
                    }
                }
            }
        }
        0x5 => {
            if (op & 0x00F8) == 0x00C8 {
                // DBcc
                Info060::new(
                    OepClass::PoepOnly,
                    CYC_060_DBCC_EXPIRED as u16,
                    F_BRANCH | F_DBCC | F_USES_CCR_LATE,
                )
            } else if (op & 0x00C0) == 0x00C0 {
                // Scc <ea>: 1 cycle but consumes the CCR late.
                Info060::new(
                    OepClass::PoepSoep,
                    1,
                    F_USES_CCR_LATE | ea_flags(mode, reg, false, true),
                )
            } else {
                // ADDQ/SUBQ: 1 cycle, pOEP|sOEP.
                alu(mode, reg, true, true)
            }
        }
        0x6 => {
            // Bcc/BRA/BSR: branch path.
            Info060::new(
                OepClass::PoepOnly,
                CYC_060_BRANCH_TAKEN as u16,
                F_BRANCH
                    | if (op & 0x0F00) != 0 {
                        F_USES_CCR_LATE
                    } else {
                        0
                    },
            )
        }
        0x7 => {
            // MOVEQ: the canonical 1-cycle pOEP|sOEP instruction.
            Info060::new(OepClass::PoepSoep, 1, F_DEFINES_CCR)
        }
        0x8 => {
            if (op & 0x00C0) == 0x00C0 {
                // DIVU.W/DIVS.W: pOEP-only, data-dependent.
                Info060::new(OepClass::PoepOnly, 2, F_DEFINES_CCR | F_VARIABLE)
            } else if (op & 0x01F0) == 0x0100 || (op & 0x01F0) == 0x0140 {
                // SBCD, PACK/UNPK: pOEP-only.
                Info060::new(OepClass::PoepOnly, 2, F_DEFINES_CCR | F_VARIABLE)
            } else {
                // OR
                alu(mode, reg, true, (op & 0x0100) != 0)
            }
        }
        0x9 | 0xD => {
            if (op & 0x0130) == 0x0100 && mode <= 1 {
                // ADDX/SUBX: consume X late, pOEP-only per UM.
                Info060::new(
                    OepClass::PoepOnly,
                    1,
                    F_DEFINES_CCR | F_USES_CCR_LATE | ea_flags(mode, reg, true, true),
                )
            } else {
                // ADD/SUB/ADDA/SUBA
                alu(
                    mode,
                    reg,
                    true,
                    (op & 0x0100) != 0 && (op & 0x00C0) != 0x00C0,
                )
            }
        }
        0xB => {
            // CMP/CMPA/CMPM/EOR
            alu(
                mode,
                reg,
                true,
                (op & 0x0100) != 0 && (op & 0x00C0) != 0x00C0,
            )
        }
        0xC => {
            if (op & 0x00C0) == 0x00C0 {
                // MULU.W/MULS.W: 2 cycles, pOEP-only.
                Info060::new(OepClass::PoepOnly, 2, F_DEFINES_CCR)
            } else if (op & 0x01F0) == 0x0100 {
                // ABCD
                Info060::new(OepClass::PoepOnly, 2, F_DEFINES_CCR | F_VARIABLE)
            } else if (op & 0x01F8) == 0x0140 || (op & 0x01F8) == 0x0148 || (op & 0x01F8) == 0x0188
            {
                // EXG: pOEP-only per UM.
                Info060::new(OepClass::PoepOnly, 1, 0)
            } else {
                // AND
                alu(mode, reg, true, (op & 0x0100) != 0)
            }
        }
        0xE => {
            if (op & 0x08C0) == 0x08C0 {
                // Bitfields: pOEP-only, data-dependent.
                unclassified
            } else if (op & 0x00C0) == 0x00C0 {
                // Memory shifts (single bit): 1 cycle.
                Info060::new(
                    OepClass::PoepSoep,
                    1,
                    F_DEFINES_CCR | F_READS_MEM | F_WRITES_MEM,
                )
            } else if (op & 0x0018) == 0x0010 {
                // ROXL/ROXR: consume X, pOEP-only.
                Info060::new(OepClass::PoepOnly, 1, F_DEFINES_CCR | F_USES_CCR_LATE)
            } else {
                // Register shifts/rotates: 1 cycle, pOEP|sOEP per UM.
                Info060::new(OepClass::PoepSoep, 1, F_DEFINES_CCR)
            }
        }
        // A-line, F-line (FPU/MMU/MOVE16/LPSTOP), and anything else: pOEP-only
        // with data-dependent cost.
        _ => unclassified,
    }
}

/// Registers an instruction uses and defines (D0-D7 = bits 0-7,
/// A0-A7 = bits 8-15), decoded from the opcode word alone for the pairing
/// dependency test. Extension-word index registers are invisible here,
/// which is safe: indexed EAs classify pOEP-only and never pair. Anything
/// not decoded returns full masks - pessimistic, so pairing is blocked
/// rather than wrongly allowed.
pub fn reg_masks_060(op: u16) -> (u16, u16) {
    let mode = (op >> 3) & 7;
    let reg = op & 7;
    let full = (0xFFFFu16, 0xFFFFu16);

    // (use, def) contributed by a standard EA field. The operand value
    // use/def is the caller's business; this covers address registers.
    fn ea_masks(mode: u16, reg: u16) -> (u16, u16) {
        match mode {
            0 => (1 << reg, 0),           // Dn operand
            1 => (1 << (8 + reg), 0),     // An operand
            2 | 5 => (1 << (8 + reg), 0), // (An) / (d16,An)
            // (An)+ / -(An): reads and updates An.
            3 | 4 => (1 << (8 + reg), 1 << (8 + reg)),
            // Indexed: the index register is in the extension word -
            // pessimistic full use (these are pOEP-only anyway).
            6 => (0xFFFF, 0),
            _ => (0, 0), // abs / pc-rel / immediate
        }
    }

    match op >> 12 {
        // MOVE/MOVEA: src EA -> dst EA.
        0x1..=0x3 => {
            let (su, sd) = ea_masks(mode, reg);
            let dst_mode = (op >> 6) & 7;
            let dst_reg = (op >> 9) & 7;
            let (du, dd) = ea_masks(dst_mode, dst_reg);
            let extra_def = match dst_mode {
                0 => 1 << dst_reg,
                1 => 1 << (8 + dst_reg),
                _ => 0,
            };
            (su | du, sd | dd | extra_def)
        }
        // MOVEQ #imm,Dn.
        0x7 => (0, 1 << ((op >> 9) & 7)),
        // Dyadic groups: OR/SUB/CMP-EOR/AND/ADD with a Dn (or An for the
        // address forms) and an EA.
        0x8 | 0x9 | 0xB | 0xC | 0xD => {
            let opmode = (op >> 6) & 7;
            let dn = (op >> 9) & 7;
            let (eu, ed) = ea_masks(mode, reg);
            match opmode {
                // <ea>,Dn: uses EA and Dn, defines Dn.
                0..=2 => (eu | (1 << dn), ed | (1 << dn)),
                // ADDA/SUBA/CMPA <ea>,An (word/long).
                3 | 7 => (eu | (1 << (8 + dn)), ed | (1 << (8 + dn))),
                // Dn,<ea>: memory destination RMW (or the X-forms, which
                // classify pOEP-only and never reach the masks).
                _ => ((1 << dn) | eu, ed),
            }
        }
        // ADDQ/SUBQ/Scc: single EA operand.
        0x5 => {
            let (eu, ed) = ea_masks(mode, reg);
            let operand_def = match mode {
                0 => 1 << reg,
                1 => 1 << (8 + reg),
                _ => 0,
            };
            (eu, ed | operand_def)
        }
        // Register shifts/rotates define Dn; the register-count form also
        // uses the count register.
        0xE if (op & 0x00C0) != 0x00C0 => {
            let dn = op & 7;
            let count_use = if (op & 0x0020) != 0 {
                1 << ((op >> 9) & 7)
            } else {
                0
            };
            ((1 << dn) | count_use, 1 << dn)
        }
        0x4 => {
            if (op & 0x01C0) == 0x01C0 {
                // LEA <ea>,An.
                let an = (op >> 9) & 7;
                let (eu, _) = ea_masks(mode, reg);
                (eu, 1 << (8 + an))
            } else if (op & 0x0F00) < 0x0700 || (op & 0x0F00) == 0x0A00 {
                // CLR/NEG/NEGX/NOT/TST/EXT/SWAP-shaped single-EA forms.
                let (eu, ed) = ea_masks(mode, reg);
                let operand_def = if mode == 0 { 1 << reg } else { 0 };
                (eu, ed | operand_def)
            } else {
                full
            }
        }
        _ => full,
    }
}

/// The 64K classification table, built once per process. Pure function of
/// the opcode word; never serialized.
fn info_table() -> &'static [u16; 0x10000] {
    static TABLE: OnceLock<Box<[u16; 0x10000]>> = OnceLock::new();
    TABLE.get_or_init(|| {
        let mut table = vec![0u16; 0x10000];
        for (op, slot) in table.iter_mut().enumerate() {
            *slot = classify_060_opcode(op as u16).0;
        }
        table.into_boxed_slice().try_into().unwrap()
    })
}

/// Look up the packed timing entry for an opcode.
#[inline]
pub fn info_060(op: u16) -> Info060 {
    Info060(info_table()[op as usize])
}

impl CpuCore {
    /// 68060 cycle cost for the instruction that just retired normally
    /// (exception entries keep the handlers' own costs). `raw` is the
    /// handler's 68000-reference count, used for data-dependent fallbacks;
    /// `fetch_cached` says whether the opcode fetch hit the instruction
    /// cache (pairing and branch folding need a cached stream).
    pub(crate) fn cycles_060(&mut self, raw: i32, fetch_cached: bool) -> i32 {
        let info = info_060(self.ir as u16);
        let flowed = self.change_of_flow;

        if info.has(F_BRANCH) {
            // The DBcc handler does not raise change_of_flow; a loop is
            // visible as a PC that is not the fall-through (ppc + 4).
            let taken = if info.has(F_DBCC) {
                self.pc != self.ppc.wrapping_add(4)
            } else {
                flowed
            };
            // A folded branch needs an instruction to fold onto: only an
            // open pairing window lets it retire for free. This also
            // guarantees progress - a bare predicted `bra self` idle loop
            // still costs a clock per iteration instead of freezing
            // emulated time.
            let fold_target_open = self.oep060.pending_head.is_some();
            // A branch ends any open pairing window; the target starts cold.
            self.oep060.pending_head = None;
            return self.branch_cost_060(taken, info.has(F_DBCC), fetch_cached, fold_target_open);
        }
        if flowed {
            // JMP/JSR/RTS/RTE/RTR and friends: pipeline refill floor.
            self.oep060.pending_head = None;
            return fallback_cycles(raw).max(CYC_060_FLOW_MIN);
        }
        let mut cycles = if info.has(F_VARIABLE) || info.has(F_UNCLASSIFIED) {
            fallback_cycles(raw)
        } else {
            info.cycles()
        };
        if info.has(F_EA_INDEXED) {
            cycles += 1;
        }

        // Superscalar dispatch (retrospective pairing): if the previous
        // instruction left its sOEP slot open and this one satisfies the
        // dispatch test, it executes in the same clock - refund all but
        // the pair's shared cycle.
        let (use_mask, def_mask) = reg_masks_060(self.ir as u16);
        if let Some(head) = self.oep060.pending_head
            && self.soep_dispatch_test(&head, info, use_mask, def_mask, fetch_cached)
        {
            self.oep060.pending_head = None;
            return (cycles - 1).max(0);
        }
        // This instruction becomes the new head when its class leaves the
        // sOEP slot open (pOEP-only occupies both dispatch positions).
        self.oep060.pending_head = match info.class() {
            OepClass::PoepSoep | OepClass::PoepButAllowsSoep | OepClass::PoepUntilLast => {
                Some(PendingHead060 {
                    def_mask,
                    defines_ccr: info.has(F_DEFINES_CCR),
                    accessed_mem: info.has(F_READS_MEM) || info.has(F_WRITES_MEM),
                    head_cached: fetch_cached,
                })
            }
            OepClass::PoepOnly => None,
        };
        cycles
    }

    /// UM Table 10-1's dispatch test, one predicate so the manual's rules
    /// transcribe in one place. Deliberately pessimistic where the opcode
    /// word cannot express the full rule (under-pairing is the safe
    /// direction).
    fn soep_dispatch_test(
        &self,
        head: &PendingHead060,
        info: Info060,
        use_mask: u16,
        def_mask: u16,
        fetch_cached: bool,
    ) -> bool {
        // PCR.ESS gates superscalar dispatch globally (68060.library sets
        // it at boot; reset state is scalar).
        if self.pcr & super::cpu::PCR_ESS == 0 {
            return false;
        }
        // Both instructions must stream from the instruction cache: an
        // uncached fetch stream is bus-limited and cannot feed two OEPs.
        if !(head.head_cached && fetch_cached) {
            return false;
        }
        // Only pOEP|sOEP instructions with a simple EA may dispatch to the
        // secondary pipeline.
        if info.class() != OepClass::PoepSoep
            || info.has(F_EA_INDEXED)
            || info.has(F_UNCLASSIFIED)
            || info.has(F_VARIABLE)
        {
            return false;
        }
        // No same-cycle pOEP -> sOEP forwarding: RAW and WAW both block.
        if (use_mask | def_mask) & head.def_mask != 0 {
            return false;
        }
        // A late CCR consumer cannot pair behind a CCR producer.
        if info.has(F_USES_CCR_LATE) && head.defines_ccr {
            return false;
        }
        // v1: at most one memory operand per pair.
        if head.accessed_mem && (info.has(F_READS_MEM) || info.has(F_WRITES_MEM)) {
            return false;
        }
        true
    }

    /// Clear any open pairing window. Execution-boundary callers use
    /// `clear_execution_pipeline_state` so every CPU model is reset together.
    #[inline]
    pub(crate) fn break_060_pipeline(&mut self) {
        self.oep060.pending_head = None;
    }

    /// Branch cost: static refill numbers with the branch cache disabled;
    /// with CACR.EBC set, a correctly predicted taken branch folds to zero
    /// cycles, a correct not-taken costs one, and everything else pays the
    /// mispredict refill.
    fn branch_cost_060(
        &mut self,
        taken: bool,
        is_dbcc: bool,
        fetch_cached: bool,
        fold_target_open: bool,
    ) -> i32 {
        if self.cacr & super::cpu::CACR_060_EBC == 0 || !fetch_cached {
            return match (is_dbcc, taken) {
                (true, true) => CYC_060_DBCC_TAKEN,
                (true, false) => CYC_060_DBCC_EXPIRED,
                (false, true) => CYC_060_BRANCH_TAKEN,
                (false, false) => CYC_060_BRANCH_NOT_TAKEN,
            };
        }
        let user = !self.is_supervisor();
        let predicted_taken = self.oep060.branch_cache.predict(self.ppc).unwrap_or(false);
        let cost = match (predicted_taken, taken) {
            // Folded out of the stream when it can ride the previous
            // instruction's cycle; a lone branch still issues for a clock.
            (true, true) => i32::from(!fold_target_open),
            (false, false) => 1,
            _ => CYC_060_MISPREDICT,
        };
        self.oep060.branch_cache.update(self.ppc, taken, user);
        cost
    }

    /// Model-dispatching wrapper for the three step paths.
    #[inline]
    pub(crate) fn finalize_cycles(&mut self, raw: i32, fetch_cached: bool) -> i32 {
        match self.cpu_type {
            super::types::CpuType::M68EC020 | super::types::CpuType::M68020 => {
                self.cycles_020(raw, fetch_cached)
            }
            super::types::CpuType::M68060 => self.cycles_060(raw, fetch_cached),
            _ => self.scale_cycles_for_cpu_type(raw),
        }
    }
}