forwprop: Pattern recognize more rotates [PR94344]

forwprop: Pattern recognize more rotates [PR94344]

The following patch adjusts simplify_rotate to recognize more rotates,
basically we allow even some same precision integral -> integral
conversions, with the requirement that the RSHIFT_EXPR operand has to be
done in unsigned type (i.e. logical right shift), so that we compensate for
the combiner no longer being able to simplify those into rotates on some
targets.

2020-03-31  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/94344
	* tree-ssa-forwprop.c (simplify_rotate): Handle also same precision
	conversions, either on both operands of |^+ or just one.  Handle
	also extra same precision conversion on RSHIFT_EXPR first operand
	provided RSHIFT_EXPR is performed in unsigned type.

	* gcc.dg/pr94344.c: New test.