Altera Nios II C2H Compiler - Manual (Page 51)

Altera Corporation 9.1 3–11
November 2009 Nios II C2H Compiler User Guide
C-to-Hardware Mapping Reference
Figure 3–7. switch Logic
Subfunction Calls
A subfunction is a C function called from within an accelerated function.
The C2H Compiler translates subfunctions to hardware using the same
mapping rules as for the top-level function. The resulting HDL module
for the accelerated subfunction becomes a submodule of the top-level
function, as illustrated in
Figure 3–8 on page 3–12 .
The C2H Compiler translates the top-level function and all subfunctions
to a single hardware accelerator. The C2H Compiler creates only one
instance of the subfunction hardware logic, regardless of how many times
the subfunction is called within the top-level function. If the calling
function calls the subfunction multiple times, the subfunction logic
becomes a shared resource. However, the subfunction is a private
resource exclusive to the calling function. In other words, if multiple
separate, accelerated functions call a common subfunction, the
C2H Compiler creates separate instances of the subfunction logic.