[Bug rtl-optimization/23518] New: some gcc optimizations do not take overflow into account

[pterjan at gmail dot com]

This has been tested on 3.3.6, 3.4.1 and 4.0.1

The following test is considered always false and the block is dropped but "a"
being "int", (a + 1 < 0) is true.

[pterjan@plop tmp]$ cat lim.c
#include <stdio.h>
#include <limits.h>

int main (void)
{
        int a = INT_MAX;
        if ((a < 0) || (a + 1 < 0)) {
                printf("Hello !\n");
        }
        return 0;
}
[pterjan@plop tmp]$ gcc -O0 lim.c ; ./a.out
Hello !
[pterjan@plop tmp]$ gcc -O1 lim.c ; ./a.out
[pterjan@plop tmp]$

-- 
           Summary: some gcc optimizations do not take overflow into account
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pterjan at gmail dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23518