PR tree-optimization/34371
	* tree-vectorizer.h (struct _loop_vec_info): Add num_iters_unchanged
	field.
	(LOOP_VINFO_NITERS_UNCHANGED): Define to num_iters_unchanged field.
	* tree-vectorizer.c (set_prologue_iterations,
	slpeel_tree_peel_loop_to_edge): Call unshare_expr on
	LOOP_VINFO_NITERS_UNCHANGED before using it.

	* gcc.c-torture/compile/20071207-1.c: New test.

From-SVN: r130755