Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1748

PSUBB/PSUBW/PSUBD—Packed Subtract
Opcode
0F F8 /r
0F F9 /r
0F FA /r
Description
Subtracts the individual data elements (bytes, words, or doublewords) of the source
operand (second operand) from the individual data elements of the destination operand
(first operand). (See
the specified data type (overflows), the result is wrapped around, meaning that the
result is truncated so that only the lower (least significant) bits of the result are
returned (that is, the carry is ignored).
The destination operand must be an MMX technology register; the source operand can
be either an MMX technology register or a quadword memory location.
Figure 3-19.
mm
mm/m64
mm
The PSUBB instruction subtracts the bytes of the source operand from the bytes of the
destination operand and stores the results to the destination operand. When an
individual result is too large to be represented in 8 bits, the lower 8 bits of the result
are written to the destination operand and therefore the result wraps around.
The PSUBW instruction subtracts the words of the source operand from the words of the
destination operand and stores the results to the destination operand. When an
individual result is too large to be represented in 16 bits, the lower 16 bits of the result
are written to the destination operand and therefore the result wraps around.
The PSUBD instruction subtracts the doublewords of the source operand from the
doublewords of the destination operand and stores the results to the destination
operand. When an individual result is too large to be represented in 32 bits, the lower
32 bits of the result are written to the destination operand and therefore the result
wraps around.
4:446
Instruction
PSUBB mm, mm/m64
PSUBW mm, mm/m64
PSUBD mm, mm/m64
Figure 3-19.) If the result of a subtraction exceeds the range for
Operation of the PSUBW Instruction
PSUBW mm, mm/m64
–
Description
Subtract packed bytes in mm/m64 from packed bytes in mm .
Subtract packed words in mm/m64 from packed words in mm .
Subtract packed doublewords in mm/m64 from packed
doublewords in mm .
1000000000000000
– –
0000000000000001
0111111111111111
®
Volume 4: IA-32 Intel MMX™ Technology Instruction Reference
0111111100111000
–
1110100011111001
1001011000111111
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