When using a dsPIC microcontroller with the XC16 compiler (and without special DSP libraries) is the DSP engine used at all, if the code does not explicitly use the DSP accumulators or DSP instructions for multiplication, MAC, shifting, etc. ?
I'm interested to know if the compiler uses the DSP registers and instructions all the time, to optimize speed, even for non-DSP code.
As I understand it, to implement a digital filter in C, with the XC16 compiler and without specific DSP libraries, the DSP engine SFR registers should be configured from C and then the __builtin_*() functions should be used. Is this correct, or assembler code is needed?