[Bug tree-optimization/21559] New: [4.1 Regression] missed jump threading

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The following code should have no check for bytes == 0 but does on the mainline:
static int blocksize = 4096;

int bar (int);

void foo (void)
{
  int toread;
  int bytes;
  static char eof_reached = 0;

  toread = blocksize;
  bytes = 1;

  while (toread != 0)
    {
      bytes = bar (toread);
      if (bytes <= 0)
        {
          if (bytes < 0)
            continue;
          break;
        }
      toread -= bytes;
    }

  if (bytes == 0)
    eof_reached = 1;
}

This started to happen before 20050420 so it was ___not___ the jump threading changes.

-- 
           Summary: [4.1 Regression] missed jump threading
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21559