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Optimizing for SIMD Integer Applications 4
4-31
The subtraction operation presented above is an absolute difference, that
is,
t = abs(x-y). The byte values are stored in temporary space, all
values are summed together, and the result is written into the lower
word of the destination register.
Packed Average (Byte/Word)
The pavgb and pavgw instructions add the unsigned data elements of the
source operand to the unsigned data elements of the destination register,
along with a carry-in. The results of the addition are then each
independently shifted to the right by one bit position. The high order
bits of each element are filled with the carry bits of the corresponding
sum.
The destination operand is an SIMD register. The source operand can
either be an SIMD register or a memory operand.
Figure 4-9 PSADBW Instruction Example
OM15167
MM/m64
X8 X7 X6 X5 X4 X3 X2 X1
063
MM
Y8 Y7 Y6 Y5 Y4 Y3 Y2 Y1
063
Temp
T8 T7 T6 T5 T4 T3 T2 T1
063
========
--------
MM
0..0 0..0 0..0 T1+T2+T3+T4+T5+T6+T7+T8
063