[Bug tree-optimization/97307] Optimization for pure vs. const function

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97307

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The patch will cause

FAIL: gcc.dg/vect/pr65947-3.c scan-tree-dump-times vect "LOOP VECTORIZED" 2

since the testcase has exactly such a pattern:

unsigned int
condition_reduction (unsigned int *a, unsigned int min_v, unsigned int *b)
{
  unsigned int last = N + 65;
  unsigned int aval;

  for (unsigned int i = 0; i < N; i++)
    {
      aval = a[i];
      if (b[i] < min_v)
        last = aval;
    }
  return last;
}

and sinking the aval = a[i] load causes if-conversion to no longer happen
because a[i] now appears to only conditionally trap.  It will be vectorized
with masked loads if those are available though, so I'm considering to
XFAIL it for the moment.