[PATCH 0/3][POPCOUNT]

[Kugan Vivekanandarajah <kugan dot vivekanandarajah at linaro dot org>]

When we set niter with maybe_zero, currently final_value_relacement
will not happen due to expression_expensive_p not handling. Patch 1
adds this.

With that we have the following optimized gimple.

  <bb 2> [local count: 118111601]:
  if (b_4(D) != 0)
    goto <bb 3>; [89.00%]
  else
    goto <bb 4>; [11.00%]

  <bb 3> [local count: 105119324]:
  _2 = (unsigned long) b_4(D);
  _9 = __builtin_popcountl (_2);
  c_3 = b_4(D) != 0 ? _9 : 1;

  <bb 4> [local count: 118111601]:
  # c_12 = PHI <c_3(3), 0(2)>

I assume that 1 in  b_4(D) != 0 ? _9 : 1; is OK (?) because when the
latch execute zero times for b_4 == 0 means that the body will execute
ones.

The issue here is, since we are checking if (b_4(D) != 0) before
entering the loop means we don't need to set maybe_zero. Patch 2
handles this.

With that we have
  <bb 2> [local count: 118111601]:
  if (b_4(D) != 0)
    goto <bb 3>; [89.00%]
  else
    goto <bb 4>; [11.00%]

  <bb 3> [local count: 105119324]:
  _2 = (unsigned long) b_4(D);
  _9 = __builtin_popcountl (_2);

  <bb 4> [local count: 118111601]:
  # c_12 = PHI <0(2), _9(3)>

As advised earlier, patch 3 adds phiopt support to remove this.

Bootstrap and regression testing are ongoing.

Is this OK for trunk.

Thanks,
Kugan