B-26
INSTRUCTION FORMATS AND ENCODINGS
B.4.2.Notations
Besides opcodes, two kinds of notations are found which both describe information found in the
ModR/M byte:
/digit:
(digit between 0 and 7)
Indicates that the instruction uses only the r/m (register and memory)
operand. The reg field contains the digit that provides an extension
to the instructions opcode.
/r
Indicates that the ModR/M byte of an instruction contains both a reg-
ister operand and an r/m operand.
In addition, the following abbreviations are used:
r32
Intel Architecture 32-bit integer register
xmm/m128
Indicates a 128-bit multimedia register or a 128-bit memory loca-
tion.
xmm/m64
Indicates a 128-bit multimedia register or a 64-bit memory location.
xmm/m32
Indicates a 128-bit multimedia register or a 32-bit memory location.
mm/m64
Indicates a 64-bit multimedia register or a 64-bit memory location.
imm8
Indicates an immediate 8-bit operand.
ib
Indicates that an immediate byte operand follows the opcode,
ModR/M byte or scaled-indexing byte.
When there is ambiguity, xmm1 indicates the first source operand and xmm2 the second source
operand.
Table B-18 describes the naming conventions used in the Streaming SIMD Extensions mnemon-
ics.
Table B-18. Key to Streaming SIMD Extensions Naming Convention
MnemonicDescription
PI
Packed integer qword (e.g., mm0)
PS
Packed single FP (e.g., xmm0)
SI
Scalar integer (e.g., eax)
SS
Scalar single-FP (e.g., low 32 bits of xmm0)
