re PR tree-optimization/55875 (IVopts caused miscompilation)

re PR tree-optimization/55875 (IVopts caused miscompilation)

	PR tree-optimiation/55875
	* gcc.c-torture/execute/pr55875.c: New testcase.
	* g++.dg/torture/pr55875.C: New testcase.

	* tree-ssa-loop-niter.c (number_of_iterations_cond): Add
	EVERY_ITERATION parameter.
	(number_of_iterations_exit): Check if exit is executed every
	iteration.
	(idx_infer_loop_bounds): Similarly here.
	(n_of_executions_at_most): Simplify
	to only test for cases where statement is dominated by the
	particular bound; handle correctly the "postdominance"
	test.
	(scev_probably_wraps_p): Use max loop iterations info
	as a global bound first.

From-SVN: r195054