[Bug tree-optimization/120031] New: Fails to pattern match ctz from DeBruijn

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120031

            Bug ID: 120031
           Summary: Fails to pattern match ctz from DeBruijn
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

__attribute__((noinline)) unsigned int
ZSTD_countTrailingZeros32_fallback(unsigned int  val)
{
 #ifdef USEBMI
  return  _tzcnt_u32(val);
 #elif  USECMPBMI
  return tzcntl_cmovbl(val);
#else
{
  static const unsigned int DeBruijnBytePos[32] = {0, 1, 28, 2, 29, 14, 24, 3,
            30, 22, 20, 15, 25, 17, 4, 8,
            31, 27, 13, 23, 21, 19, 16, 7,
            26, 12, 18, 6, 11, 5, 10, 9};
  return DeBruijnBytePos[((unsigned int) ((val & -(int) val) * 0x077CB531U)) >>
27];
 }
#endif
}