[Bug middle-end/88575] gcc got confused by different comparison operators

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88575

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-01-02
                 CC|                            |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  Even with -ffast-math on GIMPLE we fail to elide the MIN_EXPR in
both functions (test has a_2(D) < b_3(D)).  When doing integer operations
VRP manages to elide those.  Given we have no such thing as value-range
propagation for floats the closest we have is DOM/VN registering the
conditions and MIN_EXPR VN "failing" to lookup whether a<=b is known.

  <bb 2> [local count: 1073741825]:
  if (a_2(D) <= b_3(D))
    goto <bb 3>; [34.00%]
  else
    goto <bb 4>; [66.00%]

  <bb 3> [local count: 365072220]:
  _4 = MIN_EXPR <a_2(D), b_3(D)>;

  <bb 4> [local count: 1073741825]:
  # _1 = PHI <_4(3), 0.0(2)>
  return _1;