[Bug tree-optimization/106365] New: Miss to handle ifn .LEN_STORE in FRE

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106365

            Bug ID: 106365
           Summary: Miss to handle ifn .LEN_STORE in FRE
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: linkw at gcc dot gnu.org
  Target Milestone: ---

In regression testing for the patch to add unroll factor suggestion to
vectorizer for port rs6000, one failure got exposed on Power10 (with partial
vector in length supported). 

The test case is gcc/testsuite/gcc.dg/tree-ssa/pr84512.c

The option can be: -O3 -mcpu=power10 -fno-vect-cost-model

The resulted IR in optimized:

  <bb 2> [local count: 97603129]:
  MEM <vector(4) int> [(int *)&a] = { 0, 1, 4, 9 };
  MEM <vector(4) int> [(int *)&a + 16B] = { 16, 25, 36, 49 };
  .LEN_STORE (&MEM <int[10]> [(void *)&a + 32B], 128B, 8, { 64, 0, 0, 0, 81, 0,
0, 0, 100, 0, 0, 0, 121, 0, 0, 0 }, 0);
  vect__2.10_6 = MEM <vector(4) int> [(int *)&a];
  vect__2.10_30 = MEM <vector(4) int> [(int *)&a + 16B];
  vect_res_10.11_31 = vect__2.10_6 + vect__2.10_30;
  _33 = VEC_PERM_EXPR <vect_res_10.11_31, { 0, 0, 0, 0 }, { 2, 3, 4, 5 }>;
  _34 = vect_res_10.11_31 + _33;
  _35 = VEC_PERM_EXPR <_34, { 0, 0, 0, 0 }, { 1, 2, 3, 4 }>;
  _36 = _34 + _35;
  stmp_res_10.12_37 = BIT_FIELD_REF <_36, 32, 0>;
  _13 = a[8];
  res_3 = _13 + stmp_res_10.12_37;
  _8 = a[9];
  res_23 = res_3 + _8;
  a ={v} {CLOBBER(eol)};
  return res_23;

instead of:

int foo ()
{
  <bb 2> [local count: 97603129]:
  return 285;

}