[Bug tree-optimization/107412] New: Miss to fold LEN_{LOAD,STORE} when the specified length equal to vector length

["linkw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107412

            Bug ID: 107412
           Summary: Miss to fold LEN_{LOAD,STORE} when the specified
                    length equal to vector length
           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: ---

test case:
===
#define N 16
int src[N];
int dest[N];

void foo (){
  for (int i = 0; i < (N-1); i++)
   dest[i] = src[i];
}

===

Options: -mcpu=power10 -fno-tree-loop-distribute-patterns --param
vect-partial-vector-usage=2 -O2 -ftree-vectorize -funroll-loops
-fno-vect-cost-model

optimized gimple output:

void foo ()
{
  vector(16) unsigned char vect_2;
  vector(16) unsigned char vect_13;
  vector(16) unsigned char vect_34;
  vector(16) unsigned char vect_47;

  <bb 2> [local count: 67108864]:
  vect_2 = .LEN_LOAD (&src, 128B, 16, 0);
  .LEN_STORE (&dest, 128B, 16, vect_2, 0);
  vect_34 = .LEN_LOAD (&MEM <int[16]> [(void *)&src + 16B], 128B, 16, 0);
  .LEN_STORE (&MEM <int[16]> [(void *)&dest + 16B], 128B, 16, vect_34, 0);
  vect_47 = .LEN_LOAD (&MEM <int[16]> [(void *)&src + 32B], 128B, 16, 0);
  .LEN_STORE (&MEM <int[16]> [(void *)&dest + 32B], 128B, 16, vect_47, 0);
  vect_13 = .LEN_LOAD (&MEM <int[16]> [(void *)&src + 48B], 128B, 12, 0);
  .LEN_STORE (&MEM <int[16]> [(void *)&dest + 48B], 128B, 12, vect_13, 0);
[tail call]
  return;

}

It's expected that we only have one separated .LEN_LOAD and .LEN_STORE with
length 12, the others can adopt just normal vector load/store.