[Bug tree-optimization/126260] New: Failure to CSE BIT_FIELD_REF of different sign

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126260

            Bug ID: 126260
           Summary: Failure to CSE BIT_FIELD_REF of different sign
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

I see in .optimized for some testcase:

  unsigned int _163;
  unsigned int _164;
  int _166;

...
  vect_patt_204.14_167 = (vector(2) int) vect_patt_203.13_168;
  _166 = BIT_FIELD_REF <vect_patt_204.14_167, 32, 0>;
...
  _164 = BIT_FIELD_REF <vect_patt_204.14_167, 32, 0>;
  _163 = BIT_FIELD_REF <vect_patt_204.14_167, 32, 32>;
  _162 = _163 + _164;

_164 could be just _164 = (unsigned int) _166, possibly not profitable
in this case (_167 is live anyway).

Could be handled in some way in VN or by a match pattern with (convert!
(bit_field_ref:[us]type ...)) result.