Intel 64 and IA-32 Architectures Software Developers Manual Volume 2B, Instruction Set Reference, N-Z

4-26 Vol. 2B
INSTRUCTION SET REFERENCE, N-Z
PACKSSWB/PACKSSDW—Pack with Signed Saturation
Description
Converts packed signed word integers into packed signed byte integers (PACKSSWB)
or converts packed signed doubleword integers into packed signed word integers
(PACKSSDW), using saturation to handle overflow conditions. See Figure 4-1 for an
example of the packing operation.
The PACKSSWB instruction converts 4 or 8 signed word integers from the destination
operand (first operand) and 4 or 8 signed word integers from the source operand
(second operand) into 8 or 16 signed byte integers and stores the result in the desti-
Opcode Instruction
64-Bit
Mode
Compat/
Leg Mode Description
0F 63 /r PACKSSWB mm1,
mm2/m64
Valid Valid Converts 4 packed signed word
integers from mm1 and from
mm2/m64 into 8 packed signed
byte integers in mm1 using signed
saturation.
66 0F 63 /r PACKSSWB xmm1,
xmm2/m128
Valid Valid Converts 8 packed signed word
integers from xmm1 and from
xxm2/m128 into 16 packed
signed byte integers in xxm1
using signed saturation.
0F 6B /r PACKSSDW mm1,
mm2/m64
Valid Valid Converts 2 packed signed
doubleword integers from mm1
and from mm2/m64 into 4 packed
signed word integers in mm1
using signed saturation.
66 0F 6B /r PACKSSDW xmm1,
xmm2/m128
Valid Valid Converts 4 packed signed
doubleword integers from xmm1
and from xxm2/m128 into 8
packed signed word integers in
xxm1 using signed saturation.
Figure 4-1. Operation of the PACKSSDW Instruction Using 64-bit Operands
D
C
64-Bit SRC
64-Bit DEST
D’
C’
B’
A’
64-Bit DEST
B
A