186
MicroBlaze Processor Reference Guide
UG081 (v14.7)
Chapter 5:
MicroBlaze Instruction Set Architecture
bs
Barrel Shift
Description
Shifts the contents of register rA by the amount specified in register rB and puts the result in register
rD.
The mnemonic bsll sets the S bit (Side bit). If the S bit is set, the barrel shift is done to the left. The
mnemonics bsrl and bsra clear the S bit and the shift is done to the right.
The mnemonic bsra will set the T bit (Type bit). If the T bit is set, the barrel shift performed is
Arithmetical. The mnemonics bsrl and bsll clear the T bit and the shift performed is Logical.
Pseudocode
if S = 1 then
(rD)
←
(rA)
<<
(rB)[27:31]
else
if T = 1 then
if ((rB)[27:31])
≠
0 then
(rD)[0:(rB)[27:31]-1]
←
(rA)
[0
]
(rD)[(rB)[27:31]:31]
←
(rA)
>>
(rB)[27:31]
else
(rD)
←
(rA)
else
(rD)
←
(rA)
>>
(rB)[27:31]
Registers Altered
•
rD
Latency
•
1 cycle with
C_AREA_OPTIMIZED=0
•
2 cycles with
C_AREA_OPTIMIZED=1
Note
These instructions are optional. To use them, MicroBlaze has to be configured to use barrel shift
instructions (
C_USE_BARREL=1
).
bsrl
rD, rA, rB
Barrel Shift Right Logical
bsra
rD, rA, rB
Barrel Shift Right Arithmetical
bsll
rD, rA, rB
Barrel Shift Left Logical
0 1 0 0 0 1
rD
rA
rB
S T 0 0 0 0 0 0 0 0 0
0
6
1
1
1
6
2
1
3
1
