[Bug tree-optimization/52252] An opportunity for x86 gcc vectorizer (gain up to 3 times)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52252

--- Comment #12 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to rguent...@suse.de from comment #11)
> We're lacking a way to say one of the bit_not should be single-used,
> one multi-use would be OK and a fair trade-off - not sure if that
> would be enough here, of course.  That would mena changing to
> a condition with single_use ().

That does not fix it though. Because in this case we have:
  c_19 = ~r_16;
  m_20 = ~g_17;
  y_21 = ~b_18;
  tmp_22 = MIN_EXPR <m_20, y_21>;
  k_23 = MIN_EXPR <c_19, tmp_22>;
  _1 = c_19 - k_23;
  _3 = m_20 - k_23;
  _5 = y_21 - k_23;
  .. = k_23;

So both bit_not are used more than once.

so we have `~a - MIN<MIN<~a, ~b>, ~c>` which is the same as `MAX<MAX<a,b>,c> -
a`.

Let me file this as a seperate bug to continue the discussion there.