[Bug c/52560] if (r == -1) causes 'assuming signed overflow does not occur when simplifying conditional to constant'

[jim at meyering dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52560

--- Comment #1 from jim at meyering dot net 2012-03-12 12:30:20 UTC ---
Created attachment 26877
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26877
50-line reproducer