Table 3-4 Options For Parallel Moves And Conditional - Motorola DSP56600 Manual

Program Control
Conditional DALU Instructions
3-12
specify that the instruction will update the CCR (according to the
result and only if it is executed), by writing ".U" at the end of the
condition attribute. For example:
add
The full set of condition mnemonics may be used, thus helping
program clarity and flexibility. The condition table could be found
on Appendix A of the DSP56300 and DSP56600 Family Manuals .
The full list of the arithmetic instructions that conditional execution
attributes could be added to them is given in Table 2-1 on page 2-2.
In general, these are all Data ALU operations that allow parallel
moves. The condition attributes use the same opcode fields that are
used to specify the parallel moves, so conditional execution and
parallel moves exclude each other. The options the user has to
modify these instructions are summarized in Table 3-4.
Table 3-4 Options for Parallel Moves and Conditional Execution
Attribute
none
conditional execution
without status update
conditional execution
with status update
parallel move
Another data-changing instruction that could be executed
conditionally is Tcc (transfer on condition). This instruction could
also be used to transfer AGU registers conditionally. On the other
hand, it does not have a parallel move option—see Appendix A in
the DSP56300 and DSP56600 Family Manuals .
Conditional arithmetic instructions enable the user to replace short
jumps with fewer instructions, thus making the code more clear and
compact. For example, consider the following high-level code line:
if (A==Y0) then B=B+X0 else B=B+X1
Without conditional arithmetic instructions, the code may look like
this:
cmp
beq
Optimizing DSP56300/DSP56600 Applications
x0,a IFne.U
Syntax
IFcc
IFcc.U
x:<ea>
or y:<ea>
or both
or l:<ea>
y0,a
_TRUE
Example
add a,b
add a,b IFge
add a,b IFlt.U
add a,b x:(r0)+,a y:(r4)-,b
MOTOROLA