gnu/dist/gcc4/gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c

   1 /* { dg-do compile } */
   2 /* { dg-options "-O2 -Wunsafe-loop-optimizations" } */
   3 extern void g(void);
   4
   5 void
   6 f (unsigned n)
   7 {
   8   unsigned k;
   9   for(k = 0;k <= n;k++) /* { dg-warning "cannot optimize.*infinite loops" } */
  10     g();
  11
  12   for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
  13     g();
  14
  15   /* We used to get warning for this loop.  However, since then # of iterations
  16      analysis improved, and we can now prove that this loop does not verflow.
  17      This is because the only case when it would overflow is if n = ~0 (since
  18      ~0 is divisible by 5), and this cannot be the case, since when we got
  19      here, the previous loop exited, thus there exists k > n.  */
  20   for(k = 5;k <= n;k += 5)
  21     g();
  22
  23   /* So we need the following loop, instead.  */
  24   for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
  25     g();
  26
  27   for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
  28     g();
  29 }