Here's another strcmp optimization opportunity.  When strlen() determines that two strings are of unequal length it's safe to assume they do not compare equal.  Therefore, in the function below, the conditional with the the strcmp() call can be folded into false.

$ cat c.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout c.c
void g (const char *a, const char *b)
{
  if (__builtin_strlen (a) == __builtin_strlen (b))
    return;

  if (!__builtin_strcmp (a, b))
    __builtin_abort ();
}

;; Function g (g, funcdef_no=0, decl_uid=1892, cgraph_uid=0, symbol_order=0)

g (const char * a, const char * b)
{
  long unsigned int _1;
  long unsigned int _2;
  int _3;

  <bb 2> [local count: 10000]:
  _1 = __builtin_strlen (a_5(D));
  _2 = __builtin_strlen (b_6(D));
  if (_1 == _2)
    goto <bb 5>; [20.97%]
  else
    goto <bb 3>; [79.03%]

  <bb 3> [local count: 7903]:
  _3 = __builtin_strcmp (a_5(D), b_6(D));
  if (_3 == 0)
    goto <bb 4>; [0.04%]
  else
    goto <bb 5>; [99.96%]

  <bb 4> [count: 0]:
  __builtin_abort ();

  <bb 5> [local count: 9997]:
  return;

}