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Volume 3: Instruction Reference
pavgsub
pavgsub — Parallel Average Subtract
Format:
(
qp
) pavgsub1
r
1
=
r
2
,
r
3
one_byte_form
(
qp
) pavgsub2
r
1
=
r
2
,
r
3
two_byte_form
Description:
The unsigned data elements of GR
r
3
are subtracted from the unsigned data elements of
GR
r
2
. The results of the subtraction are then each independently shifted to the right by
one bit position. The high-order bits of each element are filled with the borrow bits of
the subtraction (the complements of the ALU carries). To prevent cumulative round-off
errors, an averaging is performed. The low-order bit of each result is set to 1 if at least
one of the two least significant bits of the corresponding difference is 1. The signed
results are placed in GR
r
1
.
Figure 2-32. Parallel Average Subtract Example
GR r
2
:
GR r
1
:
GR r
3
:
-
-
-
-
pavgsub2
or
Sum Bits
Borrow
Bit
16-bit Difference
Plus
Carry
Shift Right
1 Bit
Shift Right 1 Bit
with Average in
Low-order Bit
Содержание Itanium 9150M
Страница 1: ......
Страница 209: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault...
Страница 301: ...3 292 Volume 3 Pseudo Code Functions Intel Itanium Architecture Software Developer s Manual Rev 2 3...
Страница 405: ...3 396 Volume 3 Resource and Dependency Semantics...
Страница 406: ...3 397 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index...
Страница 407: ...3 398 Intel Itanium Architecture Software Developer s Manual Rev 2 3...
Страница 419: ...INDEX Index 12 Index for Volumes 1 2 3 and 4...
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