tree-optimization/102131 - fix niter analysis wrt overflow

tree-optimization/102131 - fix niter analysis wrt overflow

This fixes the overflow issues seen with analyzing
BASE0 + STEP0 cmp BASE1 + STEP1 as BASE0 + STEP0 - STEP1 cmp BASE1
by following the logic we have when simplifying comparisons.

2022-01-24  Richard Biener  <rguenther@suse.de>
	    Jiufu Guo  <guojiufu@linux.ibm.com>

	PR tree-optimization/100740
	PR tree-optimization/101508
	PR tree-optimization/101972
	PR tree-optimization/102131
	* tree-ssa-loop-niter.cc (number_of_iterations_cond): Properly
	constrain BASE0 + STEP0 cmp BASE1 + STEP1 to
	BASE0 + STEP0 - STEP1 cmp BASE1 transform.

	* gcc.dg/torture/pr100740.c: New testcase.
	* gcc.dg/torture/pr101508.c: Likewise.
	* gcc.dg/torture/pr101972.c: Likewise.
	* gcc.dg/torture/pr102131-1.c: Likewise.
	* gcc.dg/torture/pr102131-2.c: Likewise.
	* gcc.dg/torture/pr102131-3.c: Likewise.
	* gcc.dg/torture/pr102131-4.c: Likewise.