loop-niter: Recognize popcount idioms even with char, short and __int128 [PR95771]

loop-niter: Recognize popcount idioms even with char, short and __int128 [PR95771]

As the testcase shows, we punt unnecessarily on popcount loop idioms if
the type is smaller than int or larger than long long.
Smaller type than int can be handled by zero-extending the argument to
unsigned int, and types twice as long as long long by doing
__builtin_popcountll on both halves of the __int128.

2020-01-04  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/95771
	* tree-ssa-loop-niter.c (number_of_iterations_popcount): Handle types
	with precision smaller than int's precision and types with precision
	twice as large as long long.  Formatting fixes.

	* gcc.target/i386/pr95771.c: New test.