User Guide

134 128-Bit Media and Scientific Programming
AMD64 Technology 24592—Rev. 3.15—November 2009
Figure 4-16. Mnemonic Syntax for Typical Instruction
This example shows the PADDB mnemonic followed by two operands, a 128-bit X MM register
operand and another 128-bit XMM register or 128-bit memory operand. In most instructions that take
two operands, the first (left-most) operand is both a source operand and the destination operand. The
second (right-most) operand serves only as a source. Some instructions can have one or more prefixes
that modify default properties, as described in “Instruction Prefixes” on page 175.
Mnemonics. The following characters are used as prefixes in the mnemonics of integer instructions:
• CVT—Convert
• CVTT—Convert with truncation
• P—Packed (vector)
• PACK—Pack elements of 2x data size to 1x data size
• PUNPCK—Unpack and interleave elements
• UNPCK—Unpack and interleave elements
In addition to the above prefix characters, the following characters are used elsewhere in the
mnemonics of integer instructions:
• B—Byte
• D—Doubleword
• DQ—Double quadword
• H—High
• L—Low, or Left
• PD—Packed double-precision floating-point
• PI—Packed integer
• PS—Packed single-precision floating-point
• Q—Quadword
• R—Right
513-147.eps
Mnemonic
First Source Operand
and Destination Operand
Second Source Operand
PADDB xmm1, xmm2/mem128