Chapter 3
Ada Language Reference
3-26
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Bit-Wise Functions
A restricted set of bit-wise operations have been defined for certain
fixed-point types. These functions exist in the
SA_FIXED_BITWISE_FUNCTIONS
package found in the
sa_fxpbit_.a
and
sa_fxpbit.a
files. The set of bit-wise operations are the following
three functions:
BTEST
,
BCLEAR
, and
BSET
.
BTEST
tests the
n
th bit of a
value.
BCLEAR
clears the
n
th bit of a value.
BSET
sets the
n
th bit of a value.
The functions are overloaded to accept values that are of a fixed-point type
with radix 0. That includes
RT_SBYTE
,
RT_UBYTE
,
RT_SSHORT
,
RT_USHORT
,
RT_SLONG
, and
RT_ULONG
. Bit-wise operations on
fixed-point data types can only be done using variable blocks.
Note
The Ada templates provided by multiprocessor do not generate code that
WITH
s or
USE
s the
SA_FIXED_BITWISE_FUNCTIONS
package. If you decide to use any of those
functions, you must modify the template to include both the
WITH
and
USE
clauses for this
package. Refer to the
Template Programming Language User Guide
for information about
the templates.
Instantiated Functions Package
AutoCode/Ada will generate one additional file for a model if it
contains any fixed-point type. This file contains the package for the
RT_FIXED_OPERATORS
package. This package contains all of the
instantiations for every overload operator and conversion function that
are used in the model.
Note
All of the instantiated functions should have an Ada
pragma
directive to inline the
function. This eliminates the function call overhead associated with overloading operators.
Due to some Ada compiler inconsistencies, these directives are commented out of the
generated package. A small modification to the template can enable these directives. Refer
to the
Template Programming Language User Guide
for information about the templates.
Operator Instantiations
The
RT_FIXED_OPERATORS
package contains instantiations for
overloaded operators. These include the Ada operators:
+, -, *, /,
<, <=, >, >=, ABS
. The appropriate generic function from the
SA_FIXED_GENERICS
package is chosen to instantiate the overload.
Relational operators can be optimized if the data types of both arguments
are the same. In that case, a new function is not instantiated and the
predefined relational operator is renamed so that it is visible.
