Analyze niter for until-wrap condition [PR101145]

Analyze niter for until-wrap condition [PR101145]

For code like:
unsigned foo(unsigned val, unsigned start)
{
  unsigned cnt = 0;
  for (unsigned i = start; i > val; ++i)
    cnt++;
  return cnt;
}

The number of iterations should be about UINT_MAX - start.

There is function adjust_cond_for_loop_until_wrap which
handles similar work for const bases.
Like adjust_cond_for_loop_until_wrap, this patch enhance
function number_of_iterations_cond/number_of_iterations_lt
to analyze number of iterations for this kind of loop.

gcc/ChangeLog:

2021-08-25  Jiufu Guo  <guojiufu@linux.ibm.com>

	PR tree-optimization/101145
	* tree-ssa-loop-niter.c (number_of_iterations_until_wrap):
	New function.
	(number_of_iterations_lt): Invoke above function.
	(adjust_cond_for_loop_until_wrap):
	Merge to number_of_iterations_until_wrap.
	(number_of_iterations_cond): Update invokes for
	adjust_cond_for_loop_until_wrap and number_of_iterations_lt.

gcc/testsuite/ChangeLog:

2021-08-25  Jiufu Guo  <guojiufu@linux.ibm.com>

	PR tree-optimization/101145
	* gcc.dg/vect/pr101145.c: New test.
	* gcc.dg/vect/pr101145.inc: New test.
	* gcc.dg/vect/pr101145_1.c: New test.
	* gcc.dg/vect/pr101145_2.c: New test.
	* gcc.dg/vect/pr101145_3.c: New test.
	* gcc.dg/vect/pr101145inf.c: New test.
	* gcc.dg/vect/pr101145inf.inc: New test.
	* gcc.dg/vect/pr101145inf_1.c: New test.