ADSP-BF53x/BF56x Blackfin Processor Programming Reference
14-9
Shift/Rotate Operations
The “
ASHIFT
” versions of this instruction support two modes.
1. Default–arithmetic right shifts and logical left shifts.
Logical
left
shifts do not guarantee sign bit preservation. The “
ASHIFT
” versions
automatically select arithmetic and logical shift modes based on the
sign of the
shift_magnitude
.
2. Saturation mode–arithmetic right and left shifts that saturate if the
value is shifted left too far.
The “
>>>=
” and “
>>>
” versions of this instruction supports only arithmetic
right shifts. If left shifts are desired, the programmer must explicitly use
arithmetic “
<<
” (saturating) or logical “
<<
” (non-saturating) instructions.
L
Logical left shift instructions are duplicated in the Syntax section
for programmer convenience. See the Logical Shift instruction for
details on those operations.
The Arithmetic Shift instruction supports 16-bit and 32-bit instruction
length.
• The “
>>>=
” syntax instruction is 16 bits in length, allowing for
smaller code at the expense of flexibility.
• The “
>>>
”, “
<<
”, and “
ASHIFT
” syntax instructions are 32 bits in
length, providing a separate source and destination register, alter-
native data sizes, and parallel issue with Load/Store instructions.
Both syntaxes support constant and registered shift magnitudes.
For the
ASHIFT
versions, the sign of the shift magnitude determines the
direction of the shift.
• Positive shift magnitudes produce Logical Left shifts.
• Negative shift magnitudes produce Arithmetic Right shifts.
Содержание ADSP-BF53x Blackfin
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Страница 324: ...Instruction Overview 7 20 ADSP BF53x BF56x Blackfin Processor Programming Reference...
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Страница 742: ...Instruction Overview 19 54 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 752: ...Examples 20 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 780: ...Product Identification Register 21 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 790: ...ADSP BF535 Flags A 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 800: ...Performance Monitor Registers B 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 994: ...Instructions Listed By Operation Code C 194 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 1042: ...Index I 40 ADSP BF53x BF56x Blackfin Processor Programming Reference...