gcc/testsuite/gcc.dg/loop-versioning-6.c

   1 /* { dg-options "-O3 -fdump-tree-lversion-details" } */
   2
   3 /* The read from y in f1 will be hoisted to the outer loop.  In general
   4    it's not worth versioning outer loops when the inner loops don't also
   5    benefit.
   6
   7    This test is meant to be a slight counterexample, since versioning
   8    does lead to cheaper outer-loop vectorization.  However, the benefit
   9    isn't enough to justify the cost.  */
  10
  11 void
  12 f1 (double *restrict x, double *restrict y, int step, int n)
  13 {
  14   for (int i = 0; i < n; ++i)
  15     for (int j = 0; j < n; ++j)
  16       x[i + j] = y[i * step];
  17 }
  18
  19 /* A similar example in which the read can't be hoisted, but could
  20    for example be handled by vectorizer alias checks.  */
  21
  22 void
  23 f2 (double *x, double *y, int step, int n)
  24 {
  25   for (int i = 0; i < n; ++i)
  26     for (int j = 0; j < n; ++j)
  27       x[i + j] = y[i * step];
  28 }
  29
  30 /* { dg-final { scan-tree-dump-not {want to version} "lversion" } } */
  31 /* { dg-final { scan-tree-dump-not {versioned} "lversion" } } */