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March 2002 Release
717
Virtex-II Pro™ Platform FPGA Documentation
1-800-255-7778
Alphabetical Instruction Listing
R
sraw
Shift Right Algebraic Word
Description
The contents of register
r
S are shifted right by the number of bits specified by the contents
of register
r
B
27:31
. Bits shifted right out of the least-significant bit are lost. The most-
significant bit of register
r
S (
r
S
0
) is replicated to fill vacated bit positions on the left. The
result is loaded into register
r
A.
If
r
S contains a negative number and any 1-bits are shifted out of the least-significant bit
position, XER[CA] is set to 1. Otherwise XER[CA] is cleared to 0.
If
r
B
26
=
1, XER[CA] and all bits in register
r
A are set to the value of
r
S
0
.
Pseudocode
n
←
(
r
B)
27:31
r
←
ROTL((
r
S), 32
−
n)
if (
r
B)
26
=
0
then m
←
MASK(n, 31)
else
m
←
32
0
s
←
(
r
S)
0
(
r
A)
←
(r
∧
m)
∨
(
32
s
∧ ¬
m)
XER[CA]
←
s
∧
((r
∧ ¬
m)
≠
0)
Registers Altered
•
r
A.
•
XER[CA].
•
CR[CR0]
LT, GT, EQ, SO
if Rc
=
1.
Exceptions
•
None.
Compatibility
This instruction is defined by the PowerPC user instruction-set architecture (UISA). It is
implemented by all PowerPC processors.
sraw
r
A,
r
S
,
r
B
(Rc=0)
sraw.
r
A,
r
S
,
r
B
(Rc=1)
X Instruction Form
31
r
S
r
A
r
B
792
Rc
0
6
1
1
1
6
2
1
3
1
Содержание Virtex-II Pro PPC405
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