Re: AVR: CC0 to CCmode conversion

[Paul Schlie <schlie at comcast dot net>]

> From: Denis Chertykov <denisc@overta.ru>
>> Paul Schlie <schlie@comcast.net> writes:
>> ...
>> (Observing that I'm basically suggesting treating the cc-status register
>>  like any other hard register, who's value would need to be saved/restored
>>  around any corrupting operation if it's value has live dependants; what's
>>  preventing GCC's register and value dependency tracking logic from being
>>  able to manage its value properly just like it can for other register
>>  allocated values ?)
> 
> Why not CCmode register ?

- For what? As it would seem that as along as all rtl instruction data-flow
  dependencies are satisfied, the code will execute the program correctly ?

 (as all conditionals are effectively based upon a comparison of a result
  against 0, and GCC always converts both operands to the same type, so
  all that's necessary to know is if that type is signed or unsigned, as
  even floats compare just like signed integers. Therefore it would seem
  that the only difference between a compare operation and a subtract, is
  that it doesn't produce a value result which clobbers one of it's
  operands; otherwise they're identical, therefore arguably just an
  optimization to be used instead of a subtract when the result value
  isn't needed or invalid when comparing floats. It would seem ?)