[Bug tree-optimization/111154] vect-cost-model=dynamic triggers false warning on array operation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111154

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |88443
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-08-25
             Status|UNCONFIRMED                 |NEW
          Component|c                           |tree-optimization
             Target|                            |aarch64
           Keywords|                            |diagnostic

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  Reproduces with -O3 -march=armv8.3-a and

unsigned char desta[8];
void copya(unsigned char *src, int size)
{
  for (int i = 0; i < size; i++)
    desta[i] = src[i];
}

we end up with a peeled epilogue:

  if (_12 == niters_vector_mult_vf.6_39)
    goto <bb 26>; [12.50%]
  else
    goto <bb 6>; [87.50%]

  <bb 6> [local count: 73583527]:
  _96 = MEM[(unsigned char *)src_8(D) + 8B];
  desta[_36] = _96;
  if (size_7(D) > 9)
    goto <bb 7>; [85.71%]
  else
    goto <bb 27>; [14.29%]

  <bb 27> [local count: 10511932]:
  goto <bb 21>; [100.00%]

  <bb 7> [local count: 63071596]:
  _103 = MEM[(unsigned char *)src_8(D) + 9B];
  desta[9] = _103;
  if (size_7(D) != 10)
    goto <bb 8>; [85.71%]
  else
    goto <bb 28>; [14.29%]

  <bb 28> [local count: 9010228]:
  goto <bb 21>; [100.00%]

  <bb 8> [local count: 54061368]:
  _110 = MEM[(unsigned char *)src_8(D) + 10B];
  desta[10] = _110;
  if (size_7(D) != 11)
    goto <bb 9>; [85.71%]
  else
    goto <bb 29>; [14.29%]
...


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88443
[Bug 88443] [meta-bug] bogus/missing -Wstringop-overflow warnings