re PR tree-optimization/72817 (wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes))

	PR tree-optimization/72817
	PR tree-optimization/73450
	* tree-ssa-loop-niter.c (number_of_iterations_ne): Check
	multiple_of_p for adjusted IV.base.

	gcc/testsuite
	* gcc.dg/tree-ssa/pr72817.c: New test.
	* gcc.dg/tree-ssa/pr73450.c: New test.

From-SVN: r239494