xtensa: Improve shift operations more

xtensa: Improve shift operations more

This patch introduces funnel shifter utilization, and rearranges existing
"per-byte shift" insn patterns.

gcc/ChangeLog:

	* config/xtensa/predicates.md (logical_shift_operator,
	xtensa_shift_per_byte_operator): New predicates.
	* config/xtensa/xtensa-protos.h (xtensa_shlrd_which_direction):
	New prototype.
	* config/xtensa/xtensa.cc (xtensa_shlrd_which_direction):
	New helper function for funnel shift patterns.
	* config/xtensa/xtensa.md (ior_op): New code iterator.
	(*ashlsi3_1): Replace with new split pattern.
	(*shift_per_byte): Unify *ashlsi3_3x, *ashrsi3_3x and *lshrsi3_3x.
	(*shift_per_byte_omit_AND_0, *shift_per_byte_omit_AND_1):
	New insn-and-split patterns that redirect to *xtensa_shift_per_byte,
	in order to omit unnecessary bitwise AND operation.
	(*shlrd_reg_<code>, *shlrd_const_<code>, *shlrd_per_byte_<code>,
	*shlrd_per_byte_<code>_omit_AND):
	New insn patterns for funnel shifts.

gcc/testsuite/ChangeLog:

	* gcc.target/xtensa/funnel_shifter.c: New.