Cantelmo Software :: Goliath .NET CPU Emulator

X86 MNEMONIC INSTRUCTIONS FOR: GOLIATH .NET CPU EMULATOR

BINARY ARITHMETIC INSTRUCTIONS

The binary arithmetic instructions perform basic integer computions on operands in memory or the general-purpose registers:

ADC - Add With Carry
Sums two binary operands placing the result in the destination. If CF is set, a 1 is added to the destination.
ADD - Arithmetic Addition
Adds "src" to "dest" and replacing the original contents of "dest". Both operands are binary.
CMP - Compare

Subtracts source from destination and updates the flags but does not save result. Flags can subsequently be checked for conditions.
DEC - Decrement
Unsigned binary subtraction of one from the destination.
DIV - Divide

Unsigned binary division of accumulator by source. If the source divisor is a byte value then AX is divided by "src" and the quotient is placed in AL and the remainder in AH. If source operand is a word value, then DX:AX is divided by "src" and the quotient is stored in AX and the remainder in DX.
IDIV - Signed Integer Division

Signed binary division of accumulator by source. If source is a byte value, AX is divided by "src" and the quotient is stored in AL and the remainder in AH. If source is a word value, DX:AX is divided by "src", and the quotient is stored in AL and the remainder in DX.
INC - Increment
Adds one to destination unsigned binary operand.
MUL - Unsigned Multiply:
Unsigned multiply of the accumulator by the source. If "src" is a byte value, then AL is used as the other multiplicand and the result is placed in AX. If "src" is a word value, then AX is multiplied by "src" and DX:AX receives the result. If "src" is a double word value, then EAX is multiplied by "src" and EDX:EAX receives the result. The 386+ uses an early out algorithm which makes multiplying any size value in EAX as fast as in the 8 or 16 bit registers.
NEG - Two's Complement Negation
Subtracts the destination from 0 and saves the 2s complement of "dest" back into "dest".
SBB - Subtract with Borrow/Carry
Subtracts the source from the destination, and subtracts 1 extra if the Carry Flag is set. Results are returned in "dest".
SUB - Subtract
The source is subtracted from the destination and the result is stored in the destination.

BIT AND BYTE INSTRUCTIONS

The bit instructions test and modify individual bits in operands. The byte instructions set the value of a byte operand to indicate the status of flags in the eflags register:

TEST - Test For Bit Pattern
Performs a logical AND of the two operands updating the flags register without saving the result.
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CONTROL TRANSFER INSTRUCTIONS

The control transfer instructions control the flow of program execution:

JA
Short Jump if first operand is Above second operand (as set by CMP instruction). Unsigned.
JAE
Short Jump if first operand is Above or Equal to second operand (as set by CMP instruction). Unsigned.
JB
Short Jump if first operand is Below second operand (as set by CMP instruction). Unsigned.
JBE
Short Jump if first operand is Below or Equal to second operand (as set by CMP instruction). Unsigned.
JC
Short Jump if Carry flag is set to 1
JCXZ/JECXZ
Short Jump if CX/ECX register is 0. Uses unsigned comparision.
JE
Short Jump if first operand is Equal to second operand (as set by CMP instruction). Signed/Unsigned.
JG
Short Jump if first operand is Greater then second operand (as set by CMP instruction). Signed.
JL
Short Jump if first operand is Less then second operand (as set by CMP instruction). Signed.
JLE
Short Jump if first operand is Less or Equal to second operand (as set by CMP instruction). Signed.
JGE
Short Jump if first operand is Greater or Equal to second operand (as set by CMP instruction). Signed.
JNA
Short Jump if first operand is Not Above second operand (as set by CMP instruction). Unsigned.
JNAE
Short Jump if first operand is Not Above and Not Equal to second operand (as set by CMP instruction). Unsigned.
JNB
Short Jump if first operand is Not Below second operand (as set by CMP instruction). Unsigned.
JNBE
Short Jump if first operand is Not Below and Not Equal to second operand (as set by CMP instruction). Unsigned.
JNC
Short Jump if Carry flag is set to 0
JNE
Short Jump if first operand is Not Equal to second operand (as set by CMP instruction). Signed/Unsigned
JNG
Short Jump if first operand is Not Greater then second operand (as set by CMP instruction). Signed.
JNGE
Short Jump if first operand is Not Greater and Not Equal to second operand (as set by CMP instruction). Signed.
JNL
Short Jump if first operand is Not Less then second operand (as set by CMP instruction). Signed.
JNLE
Short Jump if first operand is Not Less and Not Equal to second operand (as set by CMP instruction). Signed.
JNP
Short Jump if No Parity (odd). Only 8 low bits of result are checked. Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions.
JNO
Short Jump if Not Overflow.
JNS
Short Jump if Not Signed (if positive). Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions.
JNZ
Short Jump if Not Zero (not equal). Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions.
JO
Short Jump if Overflow
JP
Short Jump if Parity (even). Only 8 low bits of result are checked. Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions
JPE
Short Jump if Parity Even. Only 8 low bits of result are checked. Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions
JPO
Short Jump if Parity Odd. Only 8 low bits of result are checked. Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions
JS
Short Jump if Signed (if negative). Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions
JZ
Short Jump if Zero (equal). Set by CMP, SUB, ADD, TEST, AND, OR, XOR instructions.

DATA TRANSFER INSTRUCTIONS

The data transfer instructions move data between memory and the general-purpose and segment registers, and perform operations such as conditional moves, stack access, and data conversion:

BSWAP - Byte Swap

Changes the byte order of a 32 bit register from big endian to little endian or vice versa. Result left in destination register is undefined if the operand is a 16 bit register.
CBW - Convert Byte to Word
Converts byte in AL to word Value in AX by extending sign of AL throughout register AH.
CWD - Convert Word to Doubleword
Extends sign of word in register AX throughout register DX forming a doubleword quantity in DX:AX.
CWDE - Convert Word to Extended Doubleword
Converts a signed word in AX to a signed doubleword in EAX by extending the sign bit of AX throughout EAX.
MOV - Move Byte or Word

Copies byte or word from the source operand to the destination operand. If the destination is SS interrupts are disabled except on early buggy 808x CPUs. Some CPUs disable interrupts if the destination is any of the segment registers.
MOVZX - Move with Zero Extend (386+)
Copies the value of the source operand to the destination register with the zeroes extended.
POP - Pop Word/DWord off Stack

Transfers word at the current stack top (SS:SP) to the destination then increments SP by two to point to the new stack top. CS is not a valid destination.
PUSH - Push Word onto Stack

Decrements SP by the size of the operand (two or four, byte values are sign extended) and transfers one word from source to the stack top (SS:SP).
XADD - Exchange and Add

Adds the source operand to the destination operand and stores the sum in the destination operand. However, just before storing the sum, it copies the original value of the destination operand into the source operand.
XCHG - Exchange
Exchanges contents of source and destination.

DECIMAL ARITHMETIC INSTRUCTIONS

The decimal arithmetic instructions perform decimal arithmetic on binary coded decimal (BCD) data:

AAA - Ascii Adjust for Addition
Changes contents of AL to valid unpacked decimal. The high order nibble is zeroed.
AAD - Ascii Adjust for Division

Used before dividing unpacked decimal numbers. Multiplies AH by 10 and the adds result into AL. Sets AH to zero. This instruction is also known to have an undocumented behavior.
AAM - Ascii Adjust for Multiplication

Used after multiplication of two unpacked decimal numbers, this instruction adjusts an unpacked decimal number. The high order nibble of each byte must be zeroed before using this instruction. This instruction is also known to have an undocumented behavior.
AAS - Ascii Adjust for Subtraction
Corrects result of a previous unpacked decimal subtraction in AL. High order nibble is zeroed.
DAA - Decimal Adjust for Addition
Corrects result (in AL) of a previous BCD addition operation. Contents of AL are changed to a pair of packed decimal digits.
DAS - Decimal Adjust for Subtraction

Corrects result (in AL) of a previous BCD subtraction operation. Contents of AL are changed to a pair of packed decimal digits.

FLAG CONTROL INSTRUCTIONS

The status flag control instructions operate on the bits in the eflags register:

CLC - Clear Carry
Clears the Carry Flag.
CLD - Clear Direction Flag
Clears the Direction Flag causing string instructions to increment the SI and DI index registers.
CMC - Complement Carry Flag
Toggles (inverts) the Carry Flag.
STC - Set Carry
Sets the Carry Flag to 1.
STD - Set Direction Flag
Sets the Direction Flag to 1 causing string instructions to auto-decrement ESI and EDI instead of auto-increment.

LOGICAL INSTRUCTIONS

The logical instructions perform basic logical operations on their operands:

AND - Logical And
Performs a logical AND of the two operands replacing the destination with the result.
NOT - One's Complement Negation (Logical NOT)
Inverts the bits of the "dest" operand forming the 1s complement.
OR - Inclusive Logical OR

Logical inclusive OR of the two operands returning the result in the destination. Any bit set in either operand will be set in the destination.
XOR - Exclusive OR
Performs a bitwise exclusive OR of the operands and returns the result in the destination.

MISCELLANEOUS INSTRUCTIONS

The instructions documented in this section provide a number of useful functions:

LEA - Load Effective Address
Transfers offset address of "src" to the destination register.
NOP - No Operation

This is a do nothing instruction. It results in occupation of both space and time and is most useful for patching code segments. (This is the original XCHG src,src instruction)

ROTATE INSTRUCTIONS

The rotate instructions rotate the bits in their operands:

RCL - Rotate Through Carry Left

Rotates the bits in the destination to the left "count" times with all data pushed out the left side re-entering on the right. The Carry Flag holds the last bit rotated out.
RCR - Rotate Through Carry Right

Rotates the bits in the destination to the right "count" times with all data pushed out the right side re-entering on the left. The Carry Flag holds the last bit rotated out.
ROL - Rotate Left

Rotates the bits in the destination to the left "count" times with all data pushed out the left side re-entering on the right. The Carry Flag will contain the value of the last bit rotated out.
ROR - Rotate Right

Rotates the bits in the destination to the right "count" times with all data pushed out the right side re-entering on the left. The Carry Flag will contain the value of the last bit rotated out.

SHIFT INSTRUCTIONS

The shift instructions shift the bits in their operands:

SAR - Shift Arithmetic Right

Shifts the destination right by "count" bits with the current sign bit replicated in the leftmost bit. The Carry Flag contains the last bit shifted out.
SAL/SHL - Shift Arithmetic Left / Shift Logical Left
Shifts the destination left by "count" bits with zeroes shifted in on right. The Carry Flag contains the last bit shifted out.
SHR - Shift Logical Right
Shifts the destination right by "count" bits with zeroes shifted in on the left. The Carry Flag contains the last bit shifted out.

STRING INSTRUCTIONS

The string instructions operate on strings of bytes. Operations include storing strings in memory, loading strings from memory, comparing strings, and scanning strings for substrings:

LODS[B][W][D] - Load String (B)yte/(W)ord/(D)ouble

Transfers string element addressed by DS:SI (even if an operand is supplied) to the accumulator. SI is incremented based on the size of the operand or based on the instruction used. If the Direction Flag is set SI is decremented, if the Direction Flag is clear SI is incremented. Use with REP prefixes.

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