reassoc: Optimize x > 0x1fff || y > 0x1fff into (x | y) > 0x1fff [PR56719]

reassoc: Optimize x > 0x1fff || y > 0x1fff into (x | y) > 0x1fff [PR56719]

The following patch adds an optimization mentioned in PR56719 #c8.
We already have the x != 0 && y != 0 && z != 0 into (x | y | z) != 0
and x != -1 && y != -1 && y != -1 into (x & y & z) != -1
optimizations, this patch just extends that to
x < C && y < C && z < C for power of two constants C into
(x | y | z) < C (for unsigned comparisons).

I didn't want to create too many buckets (there can be TYPE_PRECISION such
constants), so the patch instead just uses one buckets for all such
constants and loops over that bucket up to TYPE_PRECISION times.

2020-12-31  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/56719
	* tree-ssa-reassoc.c (optimize_range_tests_cmp_bitwise): Also optimize
	x < C && y < C && z < C when C is a power of two constant into
	(x | y | z) < C.

	* gcc.dg/tree-ssa/pr56719.c: New test.