[Bug tree-optimization/68894] Recognition min/max pattern with multiple arguments.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68894

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization, TREE

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> I think this is fixed on the trunk now.

Or rather improved enough so PHI_OPT could do something about if needed:

  if (_6 < _7)
    goto <bb 6>;
  else
    goto <bb 7>;

  <bb 6>:
  _22 = MIN_EXPR <_6, pretmp_25>;
  goto <bb 8>;

  <bb 7>:
  _28 = MIN_EXPR <_7, pretmp_25>;

  <bb 8>:
  # d_2 = PHI <_22(6), _28(7)>


Though we get:
.L12:
        ldr     w4, [x2, x8]
        ldr     w0, [x2, x6]
        ldr     w3, [x2, x7]
        cmp     w0, w4
        csel    w0, w0, w4, le
        cmp     w0, w3
        csel    w0, w0, w3, le
        str     w0, [x1, x2]
        add     x2, x2, 4
        cmp     x5, x2
        bne     .L12

From the assembly code which looks correct:


For aarch64 at -O3 we get:
.L18:
        ldr     q0, [x2, x7]
        add     w3, w3, 1
        ldr     q2, [x2, x5]
        ldr     q1, [x2, x6]
        smin    v0.4s, v0.4s, v2.4s
        smin    v0.4s, v0.4s, v1.4s
        str     q0, [x1, x2]
        add     x2, x2, 16
        cmp     w4, w3
        bhi     .L18



-O3 tree level:
  <bb 14>:
  # ivtmp.35_79 = PHI <0(13), ivtmp.35_78(14)>
  _42 = MEM[symbol: a1, index: ivtmp.35_79, offset: 0B];
  _43 = MEM[symbol: a2, index: ivtmp.35_79, offset: 0B];
  pretmp_44 = MEM[symbol: a3, index: ivtmp.35_79, offset: 0B];
  _45 = MIN_EXPR <_42, pretmp_44>;
  _46 = MIN_EXPR <_43, pretmp_44>;
  d_47 = _42 < _43 ? _45 : _46;
  MEM[base: c_12(D), index: ivtmp.35_79, offset: 0B] = d_47;
  ivtmp.35_78 = ivtmp.35_79 + 4;
  if (ivtmp.35_78 == _111)
    goto <bb 12>;
  else
    goto <bb 14>;

As you can see it does the right thing for the vectorized code.
Though in both cases it is not done at the tree level only at the RTL level.