/**
 * @fileoverview Defines PCx86 constants.
 * @author <a href="mailto:Jeff@pcjs.org">Jeff Parsons</a>
 * @copyright © Jeff Parsons 2012-2017
 *
 * This file is part of PCjs, a computer emulation software project at <http://pcjs.org/>.
 *
 * PCjs is free software: you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * PCjs is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with PCjs.  If not,
 * see <http://www.gnu.org/licenses/gpl.html>.
 *
 * You are required to include the above copyright notice in every modified copy of this work
 * and to display that copyright notice when the software starts running; see COPYRIGHT in
 * <http://pcjs.org/modules/shared/lib/defines.js>.
 *
 * Some PCjs files also attempt to load external resource files, such as character-image files,
 * ROM files, and disk image files. Those external resource files are not considered part of PCjs
 * for purposes of the GNU General Public License, and the author does not claim any copyright
 * as to their contents.
 */

"use strict";

var X86 = {
    /*
     * CPU model numbers (supported)
     */
    MODEL_8086:     8086,
    MODEL_8088:     8088,
    MODEL_80186:    80186,
    MODEL_80188:    80188,
    MODEL_80286:    80286,
    MODEL_80386:    80386,

    /*
     * 80386 CPU stepping identifiers (supported)
     */
    STEPPING_80386_A0: (80386+0xA0),    // we have very little information about this stepping...
    STEPPING_80386_A1: (80386+0xA1),    // we know much more about the A1 stepping (see /blog/2015/02/23/README.md)
    STEPPING_80386_B0: (80386+0xB0),    // for now, the only B0 difference in PCx86 is support for XBTS and IBTS
    STEPPING_80386_B1: (80386+0xB1),    // our implementation of the B1 stepping also includes the infamous 32-bit multiplication bug
    STEPPING_80386_B2: (80386+0xB2),    // this is an imaginary stepping that simply means "B1 without the 32-bit multiplication bug" (ie, a B1 with the "double sigma" stamp)
    STEPPING_80386_C0: (80386+0xC0),    // this presumably fixed lots of B1 issues, but it seems to have been quickly superseded by the D0
    STEPPING_80386_D0: (80386+0xD0),    // we don't have any detailed information (eg, errata) for these later steppings
    STEPPING_80386_D1: (80386+0xD1),
    STEPPING_80386_D2: (80386+0xD2),

    /*
     * This constant is used to mark points in the code where the physical address being returned
     * is invalid and should not be used.  TODO: There are still functions that will use an invalid
     * address, which is why we've tried to choose a value that causes the least harm, but ultimately,
     * we must add checks to those functions or throw special JavaScript exceptions to bypass them.
     *
     * This value is also used to indicate non-existent EA address calculations, which are usually
     * detected with "regEA === ADDR_INVALID" and "regEAWrite === ADDR_INVALID" tests.  In a 32-bit
     * CPU, -1 (ie, 0xffffffff) could actually be a valid address, so consider changing ADDR_INVALID
     * to NaN or null (which is also why all ADDR_INVALID tests should use strict equality operators).
     *
     * The main reason I'm NOT using NaN or null now is my concern that, by mixing non-numbers
     * (specifically, values outside the range of signed 32-bit integers), performance may suffer.
     *
     * WARNING: Like many of the properties defined here, ADDR_INVALID is a common constant, which the
     * Closure Compiler will happily inline (with or without @const annotations; in fact, I've yet to
     * see a @const annotation EVER improve automatic inlining).  However, if you don't make ABSOLUTELY
     * certain that this file is included BEFORE the first reference to any of these properties, that
     * automatic inlining will no longer occur.
     */
    ADDR_INVALID: -1,

    /*
     * Processor Exception Interrupts
     *
     * Of the following exceptions, all are designed to be restartable, except for 0x08 and 0x09 (and 0x0D
     * after an attempt to write to a read-only segment).
     *
     * Error codes are pushed onto the stack for 0x08 (always 0) and 0x0A through 0x0E.
     *
     * Priority: Instruction exception, TRAP, NMI, Processor Extension Segment Overrun, and finally INTR.
     *
     * All exceptions can also occur in real-mode, except where noted.  A GP_FAULT in real-mode can be triggered
     * by "any memory reference instruction that attempts to reference [a] 16-bit word at offset 0xFFFF".
     *
     * Interrupts beyond 0x10 (up through 0x1F) are reserved for future exceptions.
     *
     * Implementation Detail: For any opcode we know must generate a UD_FAULT interrupt, we invoke opInvalid(),
     * NOT opUndefined().  UD_FAULT is for INVALID opcodes, Intel's choice of term "undefined" notwithstanding.
     *
     * We reserve the term "undefined" for opcodes that require more investigation, and we invoke opUndefined()
     * ONLY until an opcode's behavior has finally been defined, at which point it becomes either valid or invalid.
     * The term "illegal" seems completely superfluous; we don't need a third way of describing invalid opcodes.
     *
     * The term "undocumented" should be limited to operations that are valid but Intel simply never documented.
     */
    EXCEPTION: {
        DE_EXC:     0x00,       // Divide Error Exception                   (#DE: fault, no error code)
        DB_EXC:     0x01,       // Debug (aka Single Step Trap) Exception   (#DB: fault or trap)
        NMI:        0x02,       // Non-Maskable Interrupt
        BP_TRAP:    0x03,       // Breakpoint Exception                     (#BP: trap)
        OF_TRAP:    0x04,       // INTO Overflow Exception                  (#OF: trap)
        BR_FAULT:   0x05,       // BOUND Error Exception                    (#BR: fault, no error code)
        UD_FAULT:   0x06,       // Invalid (aka Undefined/Illegal) Opcode   (#UD: fault, no error code)
        NM_FAULT:   0x07,       // No Math Unit Available; see ESC or WAIT  (#NM: fault, no error code)
        DF_FAULT:   0x08,       // Double Fault; see LIDT                   (#DF: fault, with error code)
        MP_FAULT:   0x09,       // Math Unit Protection Fault; see ESC      (#MP: fault, no error code)
        TS_FAULT:   0x0A,       // Invalid Task State Segment Fault         (#TS: fault, with error code; protected-mode only)
        NP_FAULT:   0x0B,       // Not Present Fault                        (#NP: fault, with error code; protected-mode only)
        SS_FAULT:   0x0C,       // Stack Fault                              (#SS: fault, with error code; protected-mode only)
        GP_FAULT:   0x0D,       // General Protection Fault                 (#GP: fault, with error code)
        PF_FAULT:   0x0E,       // Page Fault                               (#PF: fault, with error code)
        MF_FAULT:   0x10        // Math Fault; see ESC or WAIT              (#MF: fault, no error code)
    },
    /*
     * Processor Status flag definitions (stored in regPS)
     */
    PS: {
        CF:     0x0001,     // bit 0: Carry flag
        BIT1:   0x0002,     // bit 1: reserved, always set
        PF:     0x0004,     // bit 2: Parity flag
        BIT3:   0x0008,     // bit 3: reserved, always clear
        AF:     0x0010,     // bit 4: Auxiliary Carry flag (aka Arithmetic flag)
        BIT5:   0x0020,     // bit 5: reserved, always clear
        ZF:     0x0040,     // bit 6: Zero flag
        SF:     0x0080,     // bit 7: Sign flag
        TF:     0x0100,     // bit 8: Trap flag
        IF:     0x0200,     // bit 9: Interrupt flag
        DF:     0x0400,     // bit 10: Direction flag
        OF:     0x0800,     // bit 11: Overflow flag
        IOPL: {
         MASK:  0x3000,     // bits 12-13: I/O Privilege Level (always set on 8086/80186; clear on 80286 reset)
         SHIFT: 12
        },
        NT:     0x4000,     // bit 14: Nested Task flag (always set on 8086/80186; clear on 80286 reset)
        BIT15:  0x8000,     // bit 15: reserved (always set on 8086/80186; clear otherwise)
        RF:    0x10000,     // bit 16: Resume Flag (temporarily disables debug exceptions; 80386 only)
        VM:    0x20000      // bit 17: Virtual 8086 Mode (80386 only)
    },
    CR0: {
        /*
         * Machine Status Word (MSW) bit definitions
         */
        MSW: {
            PE:     0x0001, // protected-mode enabled
            MP:     0x0002, // monitor processor extension (ie, coprocessor)
            EM:     0x0004, // emulate processor extension
            TS:     0x0008, // task switch indicator
            ON:     0xFFF0, // on the 80286, these bits are always on (TODO: Verify)
            MASK:   0xFFFF  // these are the only (MSW) bits that the 80286 can access (within CR0)
        },
        ET: 0x00000010,     // coprocessor type (80287 or 80387); always 1 on post-80386 CPUs
        PG: 0x80000000|0    // 0: paging disabled
    },
    DR7: {                  // Debug Control Register
        L0:     0x00000001,
        G0:     0x00000002,
        L1:     0x00000004,
        G1:     0x00000008,
        L2:     0x00000010,
        G2:     0x00000020,
        L3:     0x00000040,
        G3:     0x00000080,
        ENABLE: 0x000000FF,
        LE:     0x00000100,
        GE:     0x00000200,
        RW0:    0x00030000, // 00: exec-only  01: write-only  10: undefined  11: read/write-only
        LEN0:   0x000C0000, // 00: one-byte,  01: two-byte,   10: undefined  11: four-byte
        RW1:    0x00300000, // 00: exec-only  01: write-only  10: undefined  11: read/write-only
        LEN1:   0x00C00000, // 00: one-byte,  01: two-byte,   10: undefined  11: four-byte
        RW2:    0x03000000, // 00: exec-only  01: write-only  10: undefined  11: read/write-only
        LEN2:   0x0C000000, // 00: one-byte,  01: two-byte,   10: undefined  11: four-byte
        RW3:    0x30000000, // 00: exec-only  01: write-only  10: undefined  11: read/write-only
        LEN3:   0xC0000000|0// 00: one-byte,  01: two-byte,   10: undefined  11: four-byte
    },
    DR6: {                  // Debug Status Register
        B0:     0x00000001,
        B1:     0x00000002,
        B2:     0x00000004,
        B3:     0x00000008,
        BD:     0x00002000, // set if the next instruction will read or write one of the eight debug registers and ICE-386 is also using them
        BS:     0x00004000, // set if the debug handler is entered due to the TF (trap flag) bit set in the EFLAGS register
        BT:     0x00008000  // set before entering the DEBUG handler if a task switch has occurred and the T-bit of the new TSS is set
    },
    SEL: {
        RPL:    0x0003,     // requested privilege level (0-3)
        LDT:    0x0004,     // table indicator (0: GDT, 1: LDT)
        MASK:   0xFFF8      // table offset
    },
    DESC: {                 // Descriptor Table Entry
        LIMIT: {            // LIMIT bits 0-15 (or OFFSET if this is an INTERRUPT or TRAP gate)
            OFFSET:     0x0
        },
        BASE: {             // BASE bits 0-15 (or SELECTOR if this is a TASK, INTERRUPT or TRAP gate)
            OFFSET:     0x2
        },
        ACC: {              // bit definitions for the access word (offset 0x4)
            OFFSET:     0x4,
            BASE1623:                       0x00FF,     // (not used if this a TASK, INTERRUPT or TRAP gate; bits 0-5 are parm count for CALL gates)
            TYPE: {
                OFFSET: 0x5,
                MASK:                       0x1F00,
                SEG:                        0x1000,
                NONSEG:                     0x0F00,
                /*
                 * The following bits apply only when SEG is set
                 */
                CODE:                       0x0800,     // set for CODE, clear for DATA
                ACCESSED:                   0x0100,     // set if accessed, clear if not accessed
                READABLE:                   0x0200,     // CODE: set if readable, clear if exec-only
                WRITABLE:                   0x0200,     // DATA: set if writable, clear if read-only
                CONFORMING:                 0x0400,     // CODE: set if conforming, clear if not
                EXPDOWN:                    0x0400,     // DATA: set if expand-down, clear if not
                /*
                 * Assorted bits that apply only within NONSEG values
                 */
                TSS_BUSY:                   0x0200,
                NONSEG_386:                 0x0800,     // 80386 and up
                /*
                 * The following are all the possible (valid) types (well, except for the variations
                 * of DATA and CODE where the ACCESSED bit (0x0100) may also be set)
                 */
                TSS286:                     0x0100,
                LDT:                        0x0200,
                TSS286_BUSY:                0x0300,
                GATE_CALL:                  0x0400,
                GATE_TASK:                  0x0500,
                GATE286_INT:                0x0600,
                GATE286_TRAP:               0x0700,
                TSS386:                     0x0900,     // 80386 and up
                TSS386_BUSY:                0x0B00,     // 80386 and up
                GATE386_CALL:               0x0C00,     // 80386 and up
                GATE386_INT:                0x0E00,     // 80386 and up
                GATE386_TRAP:               0x0F00,     // 80386 and up
                CODE_OR_DATA:               0x1E00,
                DATA_READONLY:              0x1000,
                DATA_WRITABLE:              0x1200,
                DATA_EXPDOWN:               0x1400,
                DATA_EXPDOWN_WRITABLE:      0x1600,
                CODE_EXECONLY:              0x1800,
                CODE_READABLE:              0x1A00,
                CODE_CONFORMING:            0x1C00,
                CODE_CONFORMING_READABLE:   0x1E00
            },
            DPL: {
                MASK:                       0x6000,
                SHIFT:                      13
            },
            PRESENT:                        0x8000,
            INVALID:    0   // use X86.DESC.ACC.INVALID for invalid ACC values
        },
        EXT: {              // descriptor extension word (reserved on the 80286; "must be zero")
            OFFSET:     0x6,
            LIMIT1619:                      0x000F,
            AVAIL:                          0x0010,     // NOTE: set in various descriptors in OS/2
            /*
             * The BIG bit is known as the D bit for code segments; when set, all addresses and operands
             * in that code segment are assumed to be 32-bit.
             *
             * The BIG bit is known as the B bit for data segments; when set, it indicates: 1) all pushes,
             * pops, calls and returns use ESP instead of SP, and 2) the upper bound of an expand-down segment
             * is 0xffffffff instead of 0xffff.
             */
            BIG:                            0x0040,     // clear if default operand/address size is 16-bit, set if 32-bit
            LIMITPAGES:                     0x0080,     // clear if limit granularity is bytes, set if limit granularity is 4Kb pages
            BASE2431:                       0xFF00
        },
        INVALID: 0          // use X86.DESC.INVALID for invalid DESC values
    },
    LADDR: {                // linear address
        PDE: {              // index of page directory entry
            MASK:   0xFFC00000|0,
            SHIFT:  20      // (addr & DIR.MASK) >>> DIR.SHIFT yields a page directory offset (ie, index * 4)
        },
        PTE: {              // index of page table entry
            MASK:   0x003FF000,
            SHIFT:  10      // (addr & PAGE.MASK) >>> PAGE.SHIFT yields a page table offset (ie, index * 4)
        },
        OFFSET:     0x00000FFF
    },
    PTE: {
        FRAME:      0xFFFFF000|0,
        DIRTY:      0x00000040,         // page has been modified
        ACCESSED:   0x00000020,         // page has been accessed
        USER:       0x00000004,         // set for user level (CPL 3), clear for supervisor level (CPL 0-2)
        READWRITE:  0x00000002,         // set for read/write, clear for read-only (affects CPL 3 only)
        PRESENT:    0x00000001          // set for present page, clear for not-present page
    },
    TSS286: {
        PREV_TSS:   0x00,
        CPL0_SP:    0x02,   // start of values altered by task switches
        CPL0_SS:    0x04,
        CPL1_SP:    0x06,
        CPL1_SS:    0x08,
        CPL2_SP:    0x0A,
        CPL2_SS:    0x0C,
        TASK_IP:    0x0E,
        TASK_PS:    0x10,
        TASK_AX:    0x12,
        TASK_CX:    0x14,
        TASK_DX:    0x16,
        TASK_BX:    0x18,
        TASK_SP:    0x1A,
        TASK_BP:    0x1C,
        TASK_SI:    0x1E,
        TASK_DI:    0x20,
        TASK_ES:    0x22,
        TASK_CS:    0x24,
        TASK_SS:    0x26,
        TASK_DS:    0x28,   // end of values altered by task switches
        TASK_LDT:   0x2A
    },
    TSS386: {
        PREV_TSS:   0x00,
        CPL0_ESP:   0x04,   // start of values altered by task switches
        CPL0_SS:    0x08,
        CPL1_ESP:   0x0c,
        CPL1_SS:    0x10,
        CPL2_ESP:   0x14,
        CPL2_SS:    0x18,
        TASK_CR3:   0x1C,   // (not in TSS286)
        TASK_EIP:   0x20,
        TASK_PS:    0x24,
        TASK_EAX:   0x28,
        TASK_ECX:   0x2C,
        TASK_EDX:   0x30,
        TASK_EBX:   0x34,
        TASK_ESP:   0x38,
        TASK_EBP:   0x3C,
        TASK_ESI:   0x40,
        TASK_EDI:   0x44,
        TASK_ES:    0x48,
        TASK_CS:    0x4C,
        TASK_SS:    0x50,
        TASK_DS:    0x54,
        TASK_FS:    0x58,   // (not in TSS286)
        TASK_GS:    0x5C,   // (not in TSS286) end of values altered by task switches
        TASK_LDT:   0x60,
        TASK_IOPM:  0x64    // (not in TSS286)
    },
    ERRCODE: {
        EXT:        0x0001,
        IDT:        0x0002,
        LDT:        0x0004,
        SELMASK:    0xFFFC
    },
    RESULT: {
        /*
         * Flags were originally computed using 16-bit result registers:
         *
         *      CF: resultZeroCarry & resultSize (ie, 0x100 or 0x10000)
         *      PF: resultParitySign & 0xff
         *      AF: (resultParitySign ^ resultAuxOverflow) & 0x0010
         *      ZF: resultZeroCarry & (resultSize - 1)
         *      SF: resultParitySign & (resultSize >> 1)
         *      OF: (resultParitySign ^ resultAuxOverflow ^ (resultParitySign >> 1)) & (resultSize >> 1)
         *
         * I386 support requires that we now rely on 32-bit result registers:
         *
         *      resultDst, resultSrc, resultArith, resultLogic and resultType
         *
         * and flags are now computed as follows:
         *
         *      CF: ((resultDst ^ ((resultDst ^ resultSrc) & (resultSrc ^ resultArith))) & resultType)
         *      PF: (resultLogic & 0xff)
         *      AF: ((resultArith ^ (resultDst ^ resultSrc)) & 0x0010)
         *      ZF: (resultLogic & ((resultType - 1) | resultType))
         *      SF: (resultLogic & resultType)
         *      OF: (((resultDst ^ resultArith) & (resultSrc ^ resultArith)) & resultType)
         *
         * where resultType contains both a size, which must be one of BYTE (0x80), WORD (0x8000),
         * or DWORD (0x80000000), along with bits for each of the arithmetic and/or logical flags that
         * are currently "cached" in the result registers (eg, X86.RESULT.CF for carry, X86.RESULT.OF
         * for overflow, etc).
         *
         * WARNING: Do not confuse these RESULT flag definitions with the PS flag definitions.  RESULT
         * flags are used only as "cached" flag indicators, packed into bits 0-5 of resultType; they do
         * not match the actual flag bit definitions within the Processor Status (PS) register.
         *
         * Arithmetic operations should call:
         *
         *      setArithResult(dst, src, value, type)
         * eg:
         *      setArithResult(dst, src, dst+src, X86.RESULT.BYTE | X86.RESULT.ALL)
         *
         * and logical operations should call:
         *
         *      setLogicResult(value, type [, carry [, overflow]])
         *
         * Since most logical operations clear both CF and OF, most calls to setLogicResult() can omit the
         * last two optional parameters.
         *
         * The type parameter of these methods indicates both the size of the result (BYTE, WORD or DWORD)
         * and which of the flags should now be considered "cached" by the result registers.  If the previous
         * resultType specifies any flags not present in the new type parameter, then those flags are
         * calculated and written to the appropriate regPS bit(s) *before* the result registers are updated.
         *
         * Arithmetic operations are assumed to represent an "added" result; if a "subtracted" result is
         * provided instead (eg, from CMP, DEC, SUB, etc), then setArithResult() must include a 5th parameter
         * (fSubtract); eg:
         *
         *      setArithResult(dst, src, dst-src, X86.RESULT.BYTE | X86.RESULT.ALL, true)
         *
         * TODO: Consider separating setArithResult() into two functions: setAddResult() and setSubResult().
         */
        BYTE:       0x80,       // result is byte value
        WORD:       0x8000,     // result is word value
        DWORD:      0x80000000|0,
        TYPE:       0x80008080|0,
        CF:         0x01,       // carry flag is cached
        PF:         0x02,       // parity flag is cached
        AF:         0x04,       // aux carry flag is cached
        ZF:         0x08,       // zero flag is cached
        SF:         0x10,       // sign flag is cached
        OF:         0x20,       // overflow flag is cached
        ALL:        0x3F,       // all result flags are cached
        LOGIC:      0x1A,       // all logical flags are cached; see setLogicResult()
        NOTCF:      0x3E        // all result flags EXCEPT carry are cached
    },
    /*
     * Bit values for opFlags, which are all reset to zero prior to each instruction
     */
    OPFLAG: {
        NOREAD:     0x0001,     // disable memory reads for the remainder of the current instruction
        NOWRITE:    0x0002,     // disable memory writes for the remainder of the current instruction
        NOINTR:     0x0004,     // a segreg has been set, or a prefix, or an STI (delay INTR acknowledgement)
        WRAP:       0x0008,     // a segment wrap-around has occurred (relevant to 8086/8088 only)
        SEG:        0x0010,     // segment override
        LOCK:       0x0020,     // lock prefix
        REPZ:       0x0040,     // repeat while Z (NOTE: this value MUST match PS.ZF; see opCMPSb/opCMPSw/opSCASb/opSCASw)
        REPNZ:      0x0080,     // repeat while NZ
        REPEAT:     0x0100,     // an instruction is being repeated (ie, some iteration AFTER the first)
        PUSHSP:     0x0200,     // the SP register is potentially being referenced by a PUSH SP opcode, adjustment may be required
        DATASIZE:   0x0400,     // data size override
        ADDRSIZE:   0x0800,     // address size override
        FAULT:      0x1000,     // a fault occurred during the current instruction
        DBEXC:      0x2000      // a DB_EXC exception occurred during the current instruction
    },
    /*
     * Bit values for intFlags
     */
    INTFLAG: {
        NONE:       0x00,
        INTR:       0x01,       // h/w interrupt requested
        TRAP:       0x02,       // trap (INT 0x01) requested
        HALT:       0x04,       // halt (HLT) requested
        DMA:        0x08        // async DMA operation in progress
    },
    /*
     * Common opcodes (and/or any opcodes we need to refer to explicitly)
     */
    OPCODE: {
        ES:         0x26,       // opES()
        CS:         0x2E,       // opCS()
        SS:         0x36,       // opSS()
        DS:         0x3E,       // opDS()
        PUSHSP:     0x54,       // opPUSHSP()
        PUSHA:      0x60,       // opPUSHA()    (80186 and up)
        POPA:       0x61,       // opPOPA()     (80186 and up)
        BOUND:      0x62,       // opBOUND()    (80186 and up)
        ARPL:       0x63,       // opARPL()     (80286 and up)
        FS:         0x64,       // opFS()       (80386 and up)
        GS:         0x65,       // opGS()       (80386 and up)
        OS:         0x66,       // opOS()       (80386 and up)
        AS:         0x67,       // opAS()       (80386 and up)
        PUSHN:      0x68,       // opPUSHn()    (80186 and up)
        IMULN:      0x69,       // opIMULn()    (80186 and up)
        PUSH8:      0x6A,       // opPUSH8()    (80186 and up)
        IMUL8:      0x6B,       // opIMUL8()    (80186 and up)
        INSB:       0x6C,       // opINSb()     (80186 and up)
        INSW:       0x6D,       // opINSw()     (80186 and up)
        OUTSB:      0x6E,       // opOUTSb()    (80186 and up)
        OUTSW:      0x6F,       // opOUTSw()    (80186 and up)
        ENTER:      0xC8,       // opENTER()    (80186 and up)
        LEAVE:      0xC9,       // opLEAVE()    (80186 and up)
        CALLF:      0x9A,       // opCALLF()
        MOVSB:      0xA4,       // opMOVSb()
        MOVSW:      0xA5,       // opMOVSw()
        CMPSB:      0xA6,       // opCMPSb()
        CMPSW:      0xA7,       // opCMPSw()
        STOSB:      0xAA,       // opSTOSb()
        STOSW:      0xAB,       // opSTOSw()
        LODSB:      0xAC,       // opLODSb()
        LODSW:      0xAD,       // opLODSw()
        SCASB:      0xAE,       // opSCASb()
        SCASW:      0xAF,       // opSCASw()
        INT3:       0xCC,       // opINT3()
        INTN:       0xCD,       // opINTn()
        INTO:       0xCE,       // opINTO()
        IRET:       0xCF,       // opIRET()
        ESC0:       0xD8,       // opESC0()
        ESC1:       0xD9,       // opESC1()
        ESC2:       0xDA,       // opESC2()
        ESC3:       0xDB,       // opESC3()
        ESC4:       0xDC,       // opESC4()
        ESC5:       0xDD,       // opESC5()
        ESC6:       0xDE,       // opESC6()
        ESC7:       0xDF,       // opESC7()
        LOOPNZ:     0xE0,       // opLOOPNZ()
        LOOPZ:      0xE1,       // opLOOPZ()
        LOOP:       0xE2,       // opLOOP()
        CALL:       0xE8,       // opCALL()
        JMP:        0xE9,       // opJMP()      (2-byte displacement)
        JMPF:       0xEA,       // opJMPF()
        JMPS:       0xEB,       // opJMPs()     (1-byte displacement)
        LOCK:       0xF0,       // opLOCK()
        REPNZ:      0xF2,       // opREPNZ()
        REPZ:       0xF3,       // opREPZ()
        GRP4W:      0xFF,
        CALLW:      0x10FF,     // GRP4W: fnCALLw()
        CALLFDW:    0x18FF,     // GRP4W: fnCALLFdw()
        CALLMASK:   0x38FF,     // mask 2-byte GRP4W opcodes with this before comparing to CALLW or CALLFDW
        UD2:        0x0B0F      // UD2 (invalid opcode "guaranteed" to generate UD_FAULT on all post-8086 processors)
    },
    /*
     * Floating Point Unit (FPU), aka Numeric Data Processor (NDP), aka Numeric Processor Extension (NPX), aka Coprocessor definitions
     */
    FPU: {
        MODEL_8087:     8087,
        MODEL_80287:    80287,
        MODEL_80287XL:  80387,  // internally, the 80287XL was an 80387SX, so generally, we treat this as MODEL_80387
        MODEL_80387:    80387,
        CONTROL: {              // FPU Control Word
            IM:     0x0001,     // bit 0: Invalid Operation Mask
            DM:     0x0002,     // bit 1: Denormalized Operand Mask
            ZM:     0x0004,     // bit 2: Zero Divide Mask
            OM:     0x0008,     // bit 3: Overflow Mask
            UM:     0x0010,     // bit 4: Underflow Mask
            PM:     0x0020,     // bit 5: Precision Mask
            EXC:    0x003F,     // all of the above exceptions
            IEM:    0x0080,     // bit 7: Interrupt Enable Mask (0 enables interrupts, 1 masks them; 8087 only)
            PC:     0x0300,     // bits 8-9: Precision Control
            RC: {               // bits 10-11: Rounding Control
              NEAR: 0x0000,
              DOWN: 0x0400,
              UP:   0x0800,
              CHOP: 0x0C00,
              MASK: 0x0C00
            },
            IC:     0x1000,     // bit 12: Infinity Control (0 for Projective, 1 for Affine)
            UNUSED: 0xE040,     // bits 6,13-15: unused
            INIT:   0x03BF      // X86.FPU.CONTROL.IM | X86.FPU.CONTROL.DM | X86.FPU.CONTROL.ZM | X86.FPU.CONTROL.OM | X86.FPU.CONTROL.UM | X86.FPU.CONTROL.PM | X86.FPU.CONTROL.IEM | X86.FPU.CONTROL.PC
        },
        STATUS: {               // FPU Status Word
            IE:     0x0001,     // bit 0: Invalid Operation
            DE:     0x0002,     // bit 1: Denormalized Operand
            ZE:     0x0004,     // bit 2: Zero Divide
            OE:     0x0008,     // bit 3: Overflow
            UE:     0x0010,     // bit 4: Underflow
            PE:     0x0020,     // bit 5: Precision
            SF:     0x0040,     // bit 6: Stack Fault (80387 and later; triggers an Invalid Operation exception)
            EXC:    0x007F,     // all of the above exceptions
            ES:     0x0080,     // bit 7: Error/Exception Status/Summary (Interrupt Request on 8087)
            C0:     0x0100,     // bit 8: Condition Code 0
            C1:     0x0200,     // bit 9: Condition Code 1
            C2:     0x0400,     // bit 10: Condition Code 2
            ST:     0x3800,     // bits 11-13: Stack Top
            ST_SHIFT: 11,
            C3:     0x4000,     // bit 14: Condition Code 3
            CC:     0x4700,     // all condition code bits
            BUSY:   0x8000      // bit 15: Busy
        },
        TAGS: {
            VALID:  0x0,
            ZERO:   0x1,
            SPECIAL:0x2,
            EMPTY:  0x3,
            MASK:   0x3
        }
        /*
            C3 C2 C1 C0     Condition Code (CC) values following an Examine

            0  0  0  0      Valid, positive unnormalized (+Unnormal)
            0  0  0  1      Invalid, positive, exponent=0 (+NaN)
            0  0  1  0      Valid, negative, unnormalized (-Unnormal)
            0  0  1  1      Invalid, negative, exponent=0 (-NaN)
            0  1  0  0      Valid, positive, normalized (+Normal)
            0  1  0  1      Infinity, positive (+Infinity)
            0  1  1  0      Valid, negative, normalized (-Normal)
            0  1  1  1      Infinity, negative (-Infinity)
            1  0  0  0      Zero, positive (+0)
            1  0  0  1      Empty
            1  0  1  0      Zero, negative (-0)
            1  0  1  1      Empty
            1  1  0  0      Invalid, positive, exponent=0 (+Denormal)
            1  1  0  1      Empty
            1  1  1  0      Invalid, negative, exponent=0 (-Denormal)
            1  1  1  1      Empty

                            Condition Code (CC) values following an FCOM or FTST

            0  0  ?  0      ST > source operand (FCOM); ST > 0 (FTST)
            0  0  ?  1      ST < source operand (FCOM); ST < 0 (FTST)
            1  0  ?  0      ST = source operand (FCOM); ST = 0 (FTST)
            1  1  ?  1      ST is not comparable

                            Condition Code (CC) values following a Remainder

            Q1 0  Q0 Q2     Complete reduction (he three low bits of the quotient stored in C0, C3, and C1)
            ?  1  ?  ?      Incomplete reduction
         */
    },
    CYCLES_8088: {
        nWordCyclePenalty:          4,      // NOTE: accurate for the 8088/80188 only (on the 8086/80186, it applies to odd addresses only)
        nEACyclesBase:              5,      // base or index only (BX, BP, SI or DI)
        nEACyclesDisp:              6,      // displacement only
        nEACyclesBaseIndex:         7,      // base + index (BP+DI and BX+SI)
        nEACyclesBaseIndexExtra:    8,      // base + index (BP+SI and BX+DI require an extra cycle)
        nEACyclesBaseDisp:          9,      // base or index + displacement
        nEACyclesBaseIndexDisp:     11,     // base + index + displacement (BP+DI+n and BX+SI+n)
        nEACyclesBaseIndexDispExtra:12,     // base + index + displacement (BP+SI+n and BX+DI+n require an extra cycle)
        nOpCyclesAAA:               4,      // AAA, AAS, DAA, DAS, TEST acc,imm
        nOpCyclesAAD:               60,
        nOpCyclesAAM:               83,
        nOpCyclesArithRR:           3,      // ADC, ADD, AND, OR, SBB, SUB, XOR and CMP reg,reg cycle time
        nOpCyclesArithRM:           9,      // ADC, ADD, AND, OR, SBB, SUB, and XOR reg,mem (and CMP mem,reg) cycle time
        nOpCyclesArithMR:           16,     // ADC, ADD, AND, OR, SBB, SUB, and XOR mem,reg cycle time
        nOpCyclesArithMID:          1,      // ADC, ADD, AND, OR, SBB, SUB, XOR and CMP mem,imm cycle delta
        nOpCyclesCall:              19,
        nOpCyclesCallF:             28,
        nOpCyclesCallWR:            16,
        nOpCyclesCallWM:            21,
        nOpCyclesCallDM:            37,
        nOpCyclesCLI:               2,
        nOpCyclesCompareRM:         9,      // CMP reg,mem cycle time (same as nOpCyclesArithRM on an 8086 but not on a 80286)
        nOpCyclesCWD:               5,
        nOpCyclesBound:             33,     // N/A if 8086/8088, 33-35 if 80186/80188 (TODO: Determine what the range means for an 80186/80188)
        nOpCyclesInP:               10,
        nOpCyclesInDX:              8,
        nOpCyclesIncR:              3,      // INC reg, DEC reg
        nOpCyclesIncM:              15,     // INC mem, DEC mem
        nOpCyclesInt:               51,
        nOpCyclesInt3D:             1,
        nOpCyclesIntOD:             2,
        nOpCyclesIntOFall:          4,
        nOpCyclesIRet:              32,
        nOpCyclesJmp:               15,
        nOpCyclesJmpF:              15,
        nOpCyclesJmpC:              16,
        nOpCyclesJmpCFall:          4,
        nOpCyclesJmpWR:             11,
        nOpCyclesJmpWM:             18,
        nOpCyclesJmpDM:             24,
        nOpCyclesLAHF:              4,      // LAHF, SAHF, MOV reg,imm
        nOpCyclesLEA:               2,
        nOpCyclesLS:                16,     // LDS, LES
        nOpCyclesLoop:              17,     // LOOP, LOOPNZ
        nOpCyclesLoopZ:             18,     // LOOPZ, JCXZ
        nOpCyclesLoopNZ:            19,     // LOOPNZ
        nOpCyclesLoopFall:          5,      // LOOP
        nOpCyclesLoopZFall:         6,      // LOOPZ, JCXZ
        nOpCyclesMovRR:             2,
        nOpCyclesMovRM:             8,
        nOpCyclesMovMR:             9,
        nOpCyclesMovRI:             10,
        nOpCyclesMovMI:             10,
        nOpCyclesMovAM:             10,
        nOpCyclesMovMA:             10,
        nOpCyclesDivBR:             80,     // range of 80-90
        nOpCyclesDivWR:             144,    // range of 144-162
        nOpCyclesDivBM:             86,     // range of 86-96
        nOpCyclesDivWM:             154,    // range of 154-172
        nOpCyclesIDivBR:            101,    // range of 101-112
        nOpCyclesIDivWR:            165,    // range of 165-184
        nOpCyclesIDivBM:            107,    // range of 107-118
        nOpCyclesIDivWM:            171,    // range of 171-190
        nOpCyclesMulBR:             70,     // range of 70-77
        nOpCyclesMulWR:             113,    // range of 113-118
        nOpCyclesMulBM:             76,     // range of 76-83
        nOpCyclesMulWM:             124,    // range of 124-139
        nOpCyclesIMulBR:            80,     // range of 80-98
        nOpCyclesIMulWR:            128,    // range of 128-154
        nOpCyclesIMulBM:            86,     // range of 86-104
        nOpCyclesIMulWM:            134,    // range of 134-160
        nOpCyclesNegR:              3,      // NEG reg, NOT reg
        nOpCyclesNegM:              16,     // NEG mem, NOT mem
        nOpCyclesOutP:              10,
        nOpCyclesOutDX:             8,
        nOpCyclesPopAll:            51,     // N/A if 8086/8088, 51 if 80186, 83 if 80188 (TODO: Verify)
        nOpCyclesPopReg:            8,
        nOpCyclesPopMem:            17,
        nOpCyclesPushAll:           36,     // N/A if 8086/8088, 36 if 80186, 68 if 80188 (TODO: Verify)
        nOpCyclesPushReg:           11,     // NOTE: "The 8086 Book" claims this is 10, but it's an outlier....
        nOpCyclesPushMem:           16,
        nOpCyclesPushSeg:           10,
        nOpCyclesPrefix:            2,
        nOpCyclesCmpS:              18,
        nOpCyclesCmpSr0:            9-2,    // reduced by nOpCyclesPrefix
        nOpCyclesCmpSrn:            17-2,   // reduced by nOpCyclesPrefix
        nOpCyclesLodS:              12,
        nOpCyclesLodSr0:            9-2,    // reduced by nOpCyclesPrefix
        nOpCyclesLodSrn:            13-2,   // reduced by nOpCyclesPrefix
        nOpCyclesMovS:              18,
        nOpCyclesMovSr0:            9-2,    // reduced by nOpCyclesPrefix
        nOpCyclesMovSrn:            17-2,   // reduced by nOpCyclesPrefix
        nOpCyclesScaS:              15,
        nOpCyclesScaSr0:            9-2,    // reduced by nOpCyclesPrefix
        nOpCyclesScaSrn:            15-2,   // reduced by nOpCyclesPrefix
        nOpCyclesStoS:              11,
        nOpCyclesStoSr0:            9-2,    // reduced by nOpCyclesPrefix
        nOpCyclesStoSrn:            10-2,   // reduced by nOpCyclesPrefix
        nOpCyclesRet:               8,
        nOpCyclesRetn:              12,
        nOpCyclesRetF:              18,
        nOpCyclesRetFn:             17,
        nOpCyclesShift1M:           15,     // ROL/ROR/RCL/RCR/SHL/SHR/SAR reg,1
        nOpCyclesShiftCR:           8,      // ROL/ROR/RCL/RCR/SHL/SHR/SAR reg,CL
        nOpCyclesShiftCM:           20,     // ROL/ROR/RCL/RCR/SHL/SHR/SAR mem,CL
        nOpCyclesShiftCS:           2,      // this is the left-shift value used to convert the count to the cycle cost
        nOpCyclesTestRR:            3,
        nOpCyclesTestRM:            9,
        nOpCyclesTestRI:            5,
        nOpCyclesTestMI:            11,
        nOpCyclesXchgRR:            4,
        nOpCyclesXchgRM:            17,
        nOpCyclesXLAT:              11
    },
    CYCLES_80286: {
        nWordCyclePenalty:          0,
        nEACyclesBase:              0,
        nEACyclesDisp:              0,
        nEACyclesBaseIndex:         0,
        nEACyclesBaseIndexExtra:    0,
        nEACyclesBaseDisp:          0,
        nEACyclesBaseIndexDisp:     1,
        nEACyclesBaseIndexDispExtra:1,
        nOpCyclesAAA:               3,
        nOpCyclesAAD:               14,
        nOpCyclesAAM:               16,
        nOpCyclesArithRR:           2,
        nOpCyclesArithRM:           7,
        nOpCyclesArithMR:           7,
        nOpCyclesArithMID:          0,
        nOpCyclesCall:              7,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesCallF:             13,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesCallWR:            7,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesCallWM:            11,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesCallDM:            16,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesCLI:               3,
        nOpCyclesCompareRM:         6,
        nOpCyclesCWD:               2,
        nOpCyclesBound:             13,
        nOpCyclesInP:               5,
        nOpCyclesInDX:              5,
        nOpCyclesIncR:              2,
        nOpCyclesIncM:              7,
        nOpCyclesInt:               23,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesInt3D:             0,
        nOpCyclesIntOD:             1,
        nOpCyclesIntOFall:          3,
        nOpCyclesIRet:              17,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmp:               7,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmpF:              11,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmpC:              7,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmpCFall:          3,
        nOpCyclesJmpWR:             7,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmpWM:             11,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesJmpDM:             15,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesLAHF:              2,
        nOpCyclesLEA:               3,
        nOpCyclesLS:                7,
        nOpCyclesLoop:              8,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesLoopZ:             8,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesLoopNZ:            8,      // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesLoopFall:          4,
        nOpCyclesLoopZFall:         4,
        nOpCyclesMovRR:             2,      // this is actually the same as the 8086...
        nOpCyclesMovRM:             3,
        nOpCyclesMovMR:             5,
        nOpCyclesMovRI:             2,
        nOpCyclesMovMI:             3,
        nOpCyclesMovAM:             5,      // this is actually slower than the MOD/RM form of MOV AX,mem (see nOpCyclesMovRM)
        nOpCyclesMovMA:             3,
        nOpCyclesDivBR:             14,
        nOpCyclesDivWR:             22,
        nOpCyclesDivBM:             17,
        nOpCyclesDivWM:             25,
        nOpCyclesIDivBR:            17,
        nOpCyclesIDivWR:            25,
        nOpCyclesIDivBM:            20,
        nOpCyclesIDivWM:            28,
        nOpCyclesMulBR:             13,
        nOpCyclesMulWR:             21,
        nOpCyclesMulBM:             16,
        nOpCyclesMulWM:             24,
        nOpCyclesIMulBR:            13,
        nOpCyclesIMulWR:            21,
        nOpCyclesIMulBM:            16,
        nOpCyclesIMulWM:            24,
        nOpCyclesNegR:              2,
        nOpCyclesNegM:              7,
        nOpCyclesOutP:              5,
        nOpCyclesOutDX:             5,
        nOpCyclesPopAll:            19,
        nOpCyclesPopReg:            5,
        nOpCyclesPopMem:            5,
        nOpCyclesPushAll:           17,
        nOpCyclesPushReg:           3,
        nOpCyclesPushMem:           5,
        nOpCyclesPushSeg:           3,
        nOpCyclesPrefix:            0,
        nOpCyclesCmpS:              8,
        nOpCyclesCmpSr0:            5,
        nOpCyclesCmpSrn:            9,
        nOpCyclesLodS:              5,
        nOpCyclesLodSr0:            5,
        nOpCyclesLodSrn:            4,
        nOpCyclesMovS:              5,
        nOpCyclesMovSr0:            5,
        nOpCyclesMovSrn:            4,
        nOpCyclesScaS:              7,
        nOpCyclesScaSr0:            5,
        nOpCyclesScaSrn:            8,
        nOpCyclesStoS:              3,
        nOpCyclesStoSr0:            4,
        nOpCyclesStoSrn:            3,
        nOpCyclesRet:               11,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesRetn:              11,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesRetF:              15,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesRetFn:             15,     // on the 80286, this ALSO includes the number of bytes in the target instruction
        nOpCyclesShift1M:           7,
        nOpCyclesShiftCR:           5,
        nOpCyclesShiftCM:           8,
        nOpCyclesShiftCS:           0,
        nOpCyclesTestRR:            2,
        nOpCyclesTestRM:            6,
        nOpCyclesTestRI:            3,
        nOpCyclesTestMI:            6,
        nOpCyclesXchgRR:            3,
        nOpCyclesXchgRM:            5,
        nOpCyclesXLAT:              5
    },
    /*
     * TODO: All 80386 cycle counts are based on 80286 counts until I have time to hand-generate an 80386-specific table;
     * the values below are used by selected 32-bit opcode handlers only.
     */
    CYCLES_80386: {
        nEACyclesBase:              0,
        nEACyclesDisp:              0,
        nEACyclesBaseIndex:         0,
        nEACyclesBaseIndexExtra:    0,
        nEACyclesBaseDisp:          0,
        nEACyclesBaseIndexDisp:     1,
        nEACyclesBaseIndexDispExtra:1
    }
};

/*
 * BACKTRACK-related definitions (used only if BACKTRACK is defined)
 */
X86.BTINFO = {
    SP_LO:  0,
    SP_HI:  0
};

/*
 * These PS flags are always stored directly in regPS for the 8086/8088, hence the
 * "direct" designation; other processors must adjust these bits accordingly.  The final
 * adjusted value is stored in PS_DIRECT (ie, 80286 and up also include PS.IOPL.MASK and
 * PS.NT in PS_DIRECT).
 */
X86.PS_DIRECT_8086 = (X86.PS.TF | X86.PS.IF | X86.PS.DF);

/*
 * These are the default "always set" PS bits for the 8086/8088; other processors must
 * adjust these bits accordingly.  The final adjusted value is stored in PS_SET.
 */
X86.PS_SET_8086 = (X86.PS.BIT1 | X86.PS.IOPL.MASK | X86.PS.NT | X86.PS.BIT15);

/*
 * These PS arithmetic and logical flags may be "cached" across several result registers;
 * whether or not they're currently cached depends on the RESULT bits in resultType.
 */
X86.PS_CACHED = (X86.PS.CF | X86.PS.PF | X86.PS.AF | X86.PS.ZF | X86.PS.SF | X86.PS.OF);

/*
 * PS_SAHF is a subset of the arithmetic flags, and refers only to those flags that the
 * SAHF and LAHF "8080 legacy" opcodes affect.
 */
X86.PS_SAHF = (X86.PS.CF | X86.PS.PF | X86.PS.AF | X86.PS.ZF | X86.PS.SF);

/*
 * Before we zero opFlags, we first see if any of the following PREFIX bits were set.  If any were set,
 * they are OR'ed into opPrefixes; otherwise, opPrefixes is zeroed as well.  This gives prefix-conscious
 * instructions like LODS, MOVS, STOS, CMPS, etc, a way of determining which prefixes, if any, immediately
 * preceded them.
 */
X86.OPFLAG_PREFIXES = (X86.OPFLAG.SEG | X86.OPFLAG.LOCK | X86.OPFLAG.REPZ | X86.OPFLAG.REPNZ | X86.OPFLAG.DATASIZE | X86.OPFLAG.ADDRSIZE);

if (NODE) module.exports = X86;