Bug in loop optimize (invalid postinc to preinc transformation)

Wed Dec 27 21:09:00 GMT 2000

Alexandre Oliva <aoliva@redhat.com> writes:

  On Dec 27, 2000, Peter Osterlund <peter.osterlund@mailbox.swipnet.se> wrote:

  > Compiling without optimization indicates that the compiler is
  > transforming (p++ < x) into (++p < (x+1)), even when not optimizing.
  > This transformation is incorrect because x+1 wraps around.

  Overflow invokes undefined behavior.  Since incrementing p in this
  case involves overflow, I think the transformation is ok, as far as
  undefined behavior goes.

Overflow of *unsigned* types is well-defined.  

-- 
TorbjÃƒÂ¶rn