public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug tree-optimization/27285]  New: [4.1 regression] ivopts postgresql miscompilation
@ 2006-04-24 15:33 jakub at gcc dot gnu dot org
  2006-04-24 15:50 ` [Bug tree-optimization/27285] " jakub at gcc dot gnu dot org
                   ` (7 more replies)
  0 siblings, 8 replies; 9+ messages in thread
From: jakub at gcc dot gnu dot org @ 2006-04-24 15:33 UTC (permalink / raw)
  To: gcc-bugs

extern void abort (void);

struct S { unsigned char a, b, c, d[16]; };

void __attribute__ ((noinline))
foo (struct S *x, struct S *y)
{
  int a, b;
  unsigned char c, *d, *e;

  b = x->b;
  d = x->d;
  e = y->d;
  a = 0;
  while (b)
    {
      if (b >= 8)
        {
          c = 0xff;
          b -= 8;
        }
      else
        {
          c = 0xff << (8 - b);
          b = 0;
        }

      e[a] = d[a] & c;
      a++;
    }
}

int
main (void)
{
  struct S x = { 0, 25, 0, { 0xaa, 0xbb, 0xcc, 0xdd }};
  struct S y = { 0, 0, 0, { 0 }};

  foo (&x, &y);
  if (x.d[0] != y.d[0] || x.d[1] != y.d[1]
      || x.d[2] != y.d[2] || (x.d[3] & 0x80) != y.d[3])
    abort ();
   return 0;
}

On i686-linux with -O2 -m32 the loop is miscompiled, it copies over just
first 24 bits and not the 25th bit.  From quick skimming of the tree dumps,
this looks messed up by ivopts pass.  Seems to be a recent regression,
at least 20060304 GCC 4.1.x worked fine, while 20060420 does not.


-- 
           Summary: [4.1 regression] ivopts postgresql miscompilation
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org
GCC target triplet: i686-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27285


^ permalink raw reply	[flat|nested] 9+ messages in thread
end of thread, other threads:[~2006-05-08 15:30 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2006-04-24 15:33 [Bug tree-optimization/27285] New: [4.1 regression] ivopts postgresql miscompilation jakub at gcc dot gnu dot org
2006-04-24 15:50 ` [Bug tree-optimization/27285] " jakub at gcc dot gnu dot org
2006-04-24 16:18 ` pinskia at gcc dot gnu dot org
2006-04-24 21:40 ` pinskia at gcc dot gnu dot org
2006-04-24 21:41 ` pinskia at gcc dot gnu dot org
2006-04-25  7:37 ` jakub at gcc dot gnu dot org
2006-05-04  6:40 ` jakub at gcc dot gnu dot org
2006-05-04  6:44 ` jakub at gcc dot gnu dot org
2006-05-08 15:30 ` roger at eyesopen dot com

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).