[Bug c/106255] New: [suboptinal] llvm uses instructions with larger access bit width

[zhongyunde at huawei dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106255

            Bug ID: 106255
           Summary: [suboptinal] llvm uses instructions with larger access
                    bit width
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhongyunde at huawei dot com
  Target Milestone: ---

llvm uses memory access instructions with larger access bit width base on
following case, both on x86 and arm, see detail
https://gcc.godbolt.org/z/c9ja9zWEE
```
#define N 10000
void
__attribute__((noipa))
foo_pd (_Complex double* a, _Complex double* b)
{
  for (int i = 0; i != N; i++)
    a[i] = b[i];
}
```