optimization/5470: bad optimization

optimization/5470: bad optimization

[igor]

>Number:         5470
>Category:       optimization
>Synopsis:       bad optimization
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 23 14:46:08 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     igor@txc.com
>Release:        gcc-3.0.2
>Organization:
>Environment:
hppa64-hp-hpux11.00
>Description:
A test case program runs incorrectly when compiled with -O1 or higher:

#  define VERYBIGINT (9223372036854775807L) /* 2^63-1 */

unsigned long bound(unsigned long b)

{
  unsigned long w;
  printf("b=%ld\n",b);
  for(w=0;w<=b;w++)
    {
      puts("loop gets executed");
      return(w);
    }
  puts("loop doesn't get executed");
  return(-1);
}

main()

{
  printf("size of unsigned long type is %d bytes\n",sizeof(unsigned long));
  exit(bound(VERYBIGINT));
}
>How-To-Repeat:
% gcc -o hpbug hpbug.c
% ./hpbug
size of long type is 8 bytes
b=9223372036854775807
loop gets executed
% gcc  -O1 -o hpbug hpbug.c
% ./hpbug
size of long type is 8 bytes
b=9223372036854775807
loop doesn't get executed
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: