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404
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 3:
User Programming Model
R
Algebraic-Shift Instructions
shows the PowerPC
algebraic-shift
instructions. For each type of instruction
shown, the “Operation” column indicates the shift operation performed. The column also
shows, on an instruction-by-instruction basis, whether the CR0 field is updated. XER[CA]
is always updated by these instructions to reflect the result.
The shift-right-algebraic instructions can be followed by an
addze
instruction to
implement a divide-by-2
n
operation. See
, for more
information.
Figure 3-26:
Logical-Shift Examples
UG011_18_033101
Shift by 7 bits
r
S
0
31
1000_0111_0110_0101_0100_0011_0010_0001
r
A
0
31
0000_0001_0000_1110_1100_1010_1000_0110
0
31
0000_0001_0000_1110_1100_1010_1000_0110
010_0001
1000_011
r
S
0
31
1000_0111_0110_0101_0100_0011_0010_0001
r
A
0
31
1011_0010_1010_0001_1001_0000_1000_0000
0
31
1011_0010_1010_0001_1001_0000_1000_0000
Shift by 7 bits
Right Shift
Left Shift
Table 3-39:
Algebraic-Shift Instructions
Mnemonic
Name
Operation
Operand
Syntax
Shift-Right-Algebraic Immediate Instructions
r
A is loaded with the result of algebraically right-shifting (
r
S) the
number of bits specified by SH.
srawi
Shift Right Algebraic Word Immediate
CR0 is
not
updated. XER[CA] is updated to reflect
the result.
r
A,
r
S,SH
srawi.
Shift Right Algebraic Word Immediate
and Record
CR0 and XER[CA] are updated to reflect the re-
sult.
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