Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1316

• ptr16:16 and ptr16:32 – A far pointer, typically in a code segment different from
that of the instruction. The notation 16:16 indicates that the value of the pointer
has two parts. The value to the left of the colon is a 16-bit selector or value
destined for the code segment register. The value to the right corresponds to the
offset within the destination segment. The ptr16:16 symbol is used when the
instruction's operand-size attribute is 16 bits; the ptr16:32 symbol is used when
the operand-size attribute is 32 bits.
• r8 – One of the byte general-purpose registers AL, CL, DL, BL, AH, CH, DH, or BH.
• r16 – One of the word general-purpose registers AX, CX, DX, BX, SP, BP, SI, or DI.
• r32 – One of the doubleword general-purpose registers EAX, ECX, EDX, EBX, ESP,
EBP, ESI, or EDI.
• imm8 – An immediate byte value. The imm8 symbol is a signed number between –
128 and +127 inclusive. For instructions in which imm8 is combined with a word or
doubleword operand, the immediate value is sign-extended to form a word or
doubleword. The upper byte of the word is filled with the topmost bit of the
immediate value.
• imm16 – An immediate word value used for instructions whose operand-size
attribute is 16 bits. This is a number between –32,768 and +32,767 inclusive.
• imm32 – An immediate doubleword value used for instructions whose
operand-size attribute is 32 bits. It allows the use of a number between
+2,147,483,647 and -2,147,483,648 inclusive.
• r/m8 – A byte operand that is either the contents of a byte general-purpose
register (AL, BL, CL, DL, AH, BH, CH, and DH), or a byte from memory.
• r/m16 – A word general-purpose register or memory operand used for instructions
whose operand-size attribute is 16 bits. The word general-purpose registers are:
AX, BX, CX, DX, SP, BP, SI, and DI. The contents of memory are found at the
address provided by the effective address computation.
• r/m32 – A doubleword general-purpose register or memory operand used for
instructions whose operand-size attribute is 32 bits. The doubleword
general-purpose registers are: EAX, EBX, ECX, EDX, ESP, EBP, ESI, and EDI. The
contents of memory are found at the address provided by the effective address
computation.
• m – A 16- or 32-bit operand in memory.
• m8 – A byte operand in memory, usually expressed as a variable or array name,
but pointed to by the DS:(E)SI or ES:(E)DI registers. This nomenclature is used
only with the string instructions and the XLAT instruction.
• m16 – A word operand in memory, usually expressed as a variable or array name,
but pointed to by the DS:(E)SI or ES:(E)DI registers. This nomenclature is used
only with the string instructions.
• m32 – A doubleword operand in memory, usually expressed as a variable or array
name, but pointed to by the DS:(E)SI or ES:(E)DI registers. This nomenclature is
used only with the string instructions.
• m64 – A memory quadword operand in memory. This nomenclature is used only
with the CMPXCHG8B instruction.
• m16:16, m16:32 – A memory operand containing a far pointer composed of two
numbers. The number to the left of the colon corresponds to the pointer's segment
selector. The number to the right corresponds to its offset.
• m16&32, m16&16, m32&32 – A memory operand consisting of data item pairs
whose sizes are indicated on the left and the right side of the ampersand. All
4:14 Volume 4: Base IA-32 Instruction Reference