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Saturating instructions
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| Home > ARM and Thumb Instructions > Saturating instructions | |||
The saturating instructions are:
QADDQDADDQDSUBQSUBSSATUSAT.
Some of the parallel instructions are also saturating.
Saturating arithmeticThese operations are saturating (SAT).
This means that, for some value of 2n that
depends on the instruction:
for a signed saturating operation, if the full result would be less than -2
n, the result returned is -2nfor an unsigned saturating operation, if the full result would be negative, the result returned is zero
if the full result would be greater than 2
n- 1, the result returned is 2n- 1.
When any of these things occurs, it is called saturation. Some instructions set the Q flag when saturation occurs.
Note
Saturating instructions do not clear the Q flag when saturation
does not occur. To clear the Q flag, use an MSR instruction.
The Q flag can also be set by two other instructions, but these instructions do not saturate.
| Copyright © 2011-2012 ARM. All rights reserved. | ARM DUI 0588B |
| Non-Confidential | ID062912 |
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