[Bug c/37569] Loop incorrectly optimized to endless loop with -Os/-O2/-O3

[brian at dessent dot net]

------- Comment #10 from brian at dessent dot net  2008-09-18 10:45 -------
Subject: Re:  Loop incorrectly optimized to endless loop with 
 -Os/-O2/-O3

That fact that the hardware allows it doesn't change the fact that it's
still invalid in ISO C, and that is the spec that gcc follows.

Seems to me you can avoid invoking undefined behavior by:

uint16 i = 0x0FFE, sum = 0;
do {
  i -= sizeof (uint16);
  sum += *((uint16 *)i);
} while (i);


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37569