[Bug tree-optimization/126486] New: codesize regression by 17.6and potential miss optimziation cauded by r15-6657

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126486

            Bug ID: 126486
           Summary: codesize regression by 17.6and potential miss
                    optimziation cauded by r15-6657
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liuhongt at gcc dot gnu.org
  Target Milestone: ---

testcase 

```c
int g(int N_dims, int *actual_indices, const long *input_array_dims, int
max_iter) {
  int sum = 0, iter = 0, k, j, product;
  while (iter < max_iter) {
    sum = actual_indices[0];
    for (k = N_dims-1; k > 0; k--) {
      product = 1;
      for (j = k-1; j >= 0; j--)
        product *= input_array_dims[j];
      sum += actual_indices[k] * product;
    }
    iter++;
  }
  return sum;
}
```

Compile: `gcc -O2 -march=x86-64-v3 -c pr-testcase.c` (the `-march` is not
required;
plain `-O2` reproduces too).