[Bug tree-optimization/56608] [4.7/4.8 Regression] SLP seems to produce incorrect value with -ffast-math

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56608

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-13 10:43:23 UTC ---
Ick.  SLP replaces

  scale_51 = sqrt (_50);

with

  scale_51 = 0.0;

but has not eliminated all uses of it.  I have a simple fix, but really
I see no reason why DCE should not be able to remove the scalar calls given

  /* We only handle functions that do not read or clobber memory -- i.e.
     const or novops ones.  */
  if (!(gimple_call_flags (call) & (ECF_CONST | ECF_NOVOPS)))
    return NULL_TREE;