expansion: Further improve double-word modulo, division and divmod [PR97459]

expansion: Further improve double-word modulo, division and divmod [PR97459]

The following patch implements what Thomas wrote about, in particular
that we can handle also double-word divison by the constants for which
the earlier patch optimized modulo (if it would be otherwise a library
call) and that we can also easily handle such constants shifted to the left.
Unfortunately, seems CSE isn't able to optimize away the two almost
identical sequences (one to compute remainder, one to compute quotient),
probably because of the ADD_OVERFLOW introduced jumps, so the patch also
adjusts expand_DIVMOD.

2020-12-02  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/97459
	* optabs.h (expand_doubleword_divmod): Declare.
	* optabs.c (expand_doubleword_divmod): New function.
	(expand_binop): Use it.
	* internal-fn.c (expand_DIVMOD): Likewise.

	* gcc.target/i386/pr97282.c (foo): Use 123456 divisor instead of
	10.
	* gcc.dg/pr97459-1.c (TESTS): Add tests for 10, 12 and
	6144.
	* gcc.dg/pr97459-2.c (TESTS): Likewise.
	* gcc.dg/pr97459-3.c: New test.
	* gcc.dg/pr97459-4.c: New test.
	* gcc.dg/pr97459-5.c: New test.
	* gcc.dg/pr97459-6.c: New test.