[sdiy] Organisation of tasks in synth's main uP

[Noah Vawter]

pro-question time: in assembly, I rely heavily on the overflow bit  
being set to detect wrap-around, e.g. in 8-bit registers.  But these  
days I program mainly in C and I can't figure out how to access that  
overflow bit.
I have gone so far as to use 7-bit numbers and treat the MSB as an  
overflow, but does anyone know how to read the CPU's overflow bit from  
C?

thank you,
-N


On Nov 23, 2010, at 8:54 AM, Olivier Gillet wrote:

>> Most compilers aimed at embedded systems, including GCC, usually have
>> some way to place native assembler instructions in your C code
>> ("inline assembler") and have the compiler sort out all the other
>> stuff (function prologue and epilogue, etc) for you.  However  I  
>> don't
>> generally recommend it for large functions (it tends to block any
>> optimisations in that function, same with longjmp/setjmp) so best to
>> hide it away in utility functions.
>
> Same experience here... I found that avr-gcc did the "right" register
> allocation in code surrounding inlined assembly only when the assembly
> code was kept small and didn't touch too many variables. So it seems
> better (and also good from a readability and code reuse point of view)
> to keep in C the "glue" between small inlined assembly functions.
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