re PR tree-optimization/81346 (Missed constant propagation into comparison)

re PR tree-optimization/81346 (Missed constant propagation into comparison)

	PR tree-optimization/81346
	* fold-const.h (fold_div_compare, range_check_type): Declare.
	* fold-const.c (range_check_type): New function.
	(build_range_check): Use range_check_type.
	(fold_div_compare): No longer static, rewritten into
	a match.pd helper function.
	(fold_comparison): Don't call fold_div_compare here.
	* match.pd (X / C1 op C2): New optimization using fold_div_compare
	as helper function.

	* gcc.dg/tree-ssa/pr81346-1.c: New test.
	* gcc.dg/tree-ssa/pr81346-2.c: New test.
	* gcc.dg/tree-ssa/pr81346-3.c: New test.
	* gcc.dg/tree-ssa/pr81346-4.c: New test.
	* gcc.target/i386/umod-3.c: Hide comparison against 1 from the
	compiler to avoid X / C1 op C2 optimization to trigger.

From-SVN: r250338