Optimizations by compiler in a recursive program

I got motivated from tail call optimization question What Is Tail Call Optimization?

So, I decided to see how can I do it in plain C.

So, I wrote the 2 factorial programs, 1st where tail call optimization can be applied. I call this fact function as fact(n, 1).

unsigned long long int fact(int n, int cont)
{
      if(n == 0)
            return cont;

      else return fact(n-1, n * cont);
}

2nd is the normal recursion where multiple stack frames are required.

unsigned long long int fact(int n)
{
    if(n == 0)
        return 1;

    else return n * fact(n-1);
}

This is the assembly generated by a 32 bit compiler for the former with -O2

0x8048470 <fact>:   push   %ebp
0x8048471 <fact+1>: mov    %esp,%ebp
0x8048473 <fact+3>: mov    0x8(%ebp),%edx
0x8048476 <fact+6>: mov    0xc(%ebp),%eax
0x8048479 <fact+9>: test   %edx,%edx
0x804847b <fact+11>:    je     0x8048488 <fact+24>
0x804847d <fact+13>:    lea    0x0(%esi),%esi
0x8048480 <fact+16>:    imul   %edx,%eax
0x8048483 <fact+19>:    sub    $0x1,%edx
0x8048486 <fact+22>:    jne    0x8048480 <fact+16>
0x8048488 <fact+24>:    mov    %eax,%edx
0x804848a <fact+26>:    sar    $0x1f,%edx
0x804848d <fact+29>:    pop    %ebp
0x804848e <fact+30>:    ret    

This is the assembly generated by a 32 bit compiler for latter with -O2.

0x8048470 <fact>:   push   %ebp
0x8048471 <fact+1>: mov    %esp,%ebp
0x8048473 <fact+3>: push   %edi
0x8048474 <fact+4>: push   %esi
0x8048475 <fact+5>: push   %ebx
0x8048476 <fact+6>: sub    $0x14,%esp
0x8048479 <fact+9>: mov    0x8(%ebp),%eax
0x804847c <fact+12>:    movl   $0x1,-0x18(%ebp)
0x8048483 <fact+19>:    movl   $0x0,-0x14(%e