Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

Software Streaming Via Block Streaming 441
after running the software streaming code generation program on the
application code. Branch instructions be 4,1,.L3 and b .L4, as seen in Figure
32-3, are modified to bc 4,1,load2_1 and b load2_2, respectively, as seen in
Figure 32-4.
Since the last instruction of Block 2 is not a branch or a return instruction,
the instruction bl load3_0 will be appended to Block 2 from Figure
32-3 to load the subsequent block. The instruction bl load3_0 can be replaced
later by the first instruction of the block after Block 2 in order to preserve
code continuity.
3.1.2. Coping with non-interruptible sections
Some real-time applications may contain non-interruptible section(s). This
means that while the processor is executing a non-interruptible section, the
processor cannot accept interrupts. Usually, a non-interruptible section
contains instruction(s) to disable interrupts and one or more instructions to
enable interrupts. A real-time code section should not be suspended due to
missing software components since downloading software from the network
can be very long and unpredictable. Therefore, a non-interruptible real-time
section must be put in a single block.
3.1.3. Enforcing block boundaries
One drawback for randomly dividing a binary image into blocks is that some
of the code in a particular block may not be used. For instance, consider the
case where the first instruction of a block is the last instruction of the function
in the previous block. For this case, perhaps only one instruction of the entire
block (the first instruction) may be needed if the other function(s) in the block
are never called. As a result, memory and bandwidth are not efficiently used.
However, by obtaining the size of each function, the block boundaries can be
enforced to more closely match with function boundaries [12].