[Bug middle-end/29919] New: constant propogation around comparison operators breaks things on underflow

["bardwell at curl dot com" <gcc-bugzilla at gcc dot gnu dot org>]

There seems to be some constant propogation around comparison operators going
on, even with no optimization turned on which produces different behavior that
it used to with gcc-3.4.4 and different than what happens if you do some
casting.
#include <stdio.h>
int main(int argc, char *argv[])
{
int i = atoi(argv[1]);
if (0 <= (i - 1))
    printf("no casting true\n");
else
    printf("no casting false\n");
if (0 <= (signed int)((unsigned int)i - 1))
    printf("casting true\n");
else
    printf("casting false\n");
return 0;
}

produces different answers for the two comparisons if you give it INT_MIN
(-2147483647) because of over/underflow.


-- 
           Summary: constant propogation around comparison operators breaks
                    things on underflow
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bardwell at curl dot com
 GCC build triplet: gcc version 4.1.1 20061011 (Red Hat 4.1.1-30)
  GCC host triplet: i686-redhat-linux
GCC target triplet: i686-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29919