[Bug tree-optimization/53265] Warn when undefined behavior implies smaller iteration count

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265



Jakub Jelinek <jakub at gcc dot gnu.org> changed:



           What    |Removed                     |Added

----------------------------------------------------------------------------

                 CC|                            |jakub at gcc dot gnu.org



--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-29 
17:22:34 UTC ---

Other examples from

https://lists.fedoraproject.org/pipermail/devel/2013-January/175876.html

to test the potential warning (requires 32-bit integer and 64-bit long long):



void bar (void *);



void

fn1 (void)

{

  unsigned int a[128];

  int i;



  for (i = 0; i < 128; ++i)

    a[i] = i * 0x02000001;

  bar (a);

}



void

fn2 (void)

{

  unsigned long long a[128];

  int i;



  for (i = 0; i < 128; i++)

    a[i] = (i + 1LL) * 0x0123456789ABCDEFLL;

  bar (a);

}



void

fn3 (void)

{

  unsigned char a[16], b[16], c[16];

  int i;



  bar (b);

  for (i = 0; i < (int) (sizeof (a) / sizeof (a[0])); i++)

    {

      c[i + 8] = b[i];

      a[i + 8] = b[i + 8];

    }

  bar (a);

  bar (c);

}



void

fn4 (void)

{

  unsigned int *a[32], *o, i;



  bar (a);

  for (i = 0; i <= sizeof (a) / sizeof (a[0]); i++)

    {

      o = a[i];

      bar (o);

    }

}



void

fn5 (void)

{

  unsigned short a[23940];

  unsigned int b[1140];

  int j;



  bar (b);

  for (j = 0; j < 1140; j++)

    a[23940 + j - 950] = b[j];

  bar (a);

}