Code optimizer fails to detect sequential writes to adjacent parts of the same array by Dmitry Me

This behavior is observed in cl.exe 16.00.40219.1

I have this code:

int _tmain(int /*argc*/, _TCHAR* /*argv*/[])
{
    char buffer[4];
    memset( buffer, 0, sizeof( buffer ) );
    memset( buffer, 1, sizeof( buffer ) );
    memset( buffer, 1, sizeof( buffer ) / 2 );
    memset( buffer + sizeof( buffer ) / 2, 1, sizeof( buffer ) / 2 );
    buffer[0] && rand();
    return 0;
}

which I compile with /O2 and get the following disassembly:

5: int _tmain(int /*argc*/, _TCHAR* /*argv*/[])
     6: {
00401000 push        ebp
00401001 mov         ebp,esp
00401003 push        ecx
00401004 push        edi
     7:     char buffer[4];
     8:     memset( buffer, 0, sizeof( buffer ) );
     9:     memset( buffer, 1, sizeof( buffer ) );
00401005 mov         eax,1010101h
0040100A lea         edi,[buffer]
0040100D stos        dword ptr es:[edi]
    10:     memset( buffer, 1, sizeof( buffer ) / 2 );
0040100E lea         edi,[buffer]
00401011 stos        word ptr es:[edi]
    11:     memset( buffer + sizeof( buffer ) / 2, 1, sizeof( buffer ) / 2 );
00401013 lea         edi,[ebp-2]
00401016 stos        word ptr es:[edi]
    12:     buffer[0] && rand();
00401018 cmp         byte ptr [buffer],0
0040101C pop         edi
0040101D je         wmain+25h (401025h)
0040101F call        dword ptr [__imp__rand (4020A0h)]
    13:     return 0;
00401025 xor         eax,eax
    14: }
00401027 leave
00401028 ret

The compiler detected that the first memset() is seperceded by the second memset() and successfully eliminated the first memset(). Yet it failed to detect that the third and the fourth memset()s supercede the second one. The compiler should have eliminated the first and the second memset()s and merge the third and the fourth one.