target/19907: Overhaul bit extractions.

target/19907: Overhaul bit extractions.

o Logical right shift that shifts the MSB to position 0 can be performed in
  such a way that the input operand constraint can be relaxed from "0" to "r".
  This results in less register pressure.  Moreover, no scratch register is
  required in that case.

o The deprecated "extzv" pattern is replaced by "extzv<mode>" that allows
  inputs of scalar integer modes of different sizes (1 up to 4 bytes).

o Existing patterns are adjusted to the more generic "extzv<mode>" pattern.
  Some patterns are added as the middle-end has been reworked to spot
  more bit-extraction opportunities.

o A C function is used to print the asm for bit extractions, which is more
  convenient for complex output logic.

The generated code is still not optimal because RTL optimizers might still
prefer arithmetic like shift over bit-extractions.  For test cases see
also PR36884 and PR55181.

gcc/
	PR target/109907
	* config/avr/avr.md (adjust_len) [extr, extr_not]: New elements.
	(MSB, SIZE): New mode attributes.
	(any_shift): New code iterator.
	(*lshr<mode>3_split, *lshr<mode>3, lshr<mode>3)
	(*lshr<mode>3_const_split): Add constraint alternative for
	the case of shift-offset = MSB.  Ditch "length" attribute.
	(extzv<mode): New. replaces extzv.  Adjust following patterns.
	Use avr_out_extr, avr_out_extr_not to print asm.
	(*extzv.subreg.<mode>, *extzv.<mode>.subreg, *extzv.xor)
	(*extzv<mode>.ge, *neg.ashiftrt<mode>.msb, *extzv.io.lsr7): New.
	* config/avr/constraints.md (C15, C23, C31, Yil): New
	* config/avr/predicates.md (reg_or_low_io_operand)
	(const7_operand, reg_or_low_io_operand)
	(const15_operand, const_0_to_15_operand)
	(const23_operand, const_0_to_23_operand)
	(const31_operand, const_0_to_31_operand): New.
	* config/avr/avr-protos.h (avr_out_extr, avr_out_extr_not): New.
	* config/avr/avr.cc (avr_out_extr, avr_out_extr_not): New funcs.
	(lshrqi3_out, lshrhi3_out, lshrpsi3_out, lshrsi3_out): Adjust
	MSB case to new insn constraint "r" for operands[1].
	(avr_adjust_insn_length) [ADJUST_LEN_EXTR_NOT, ADJUST_LEN_EXTR]:
	Handle these cases.
	(avr_rtx_costs_1): Adjust cost for a new pattern.
gcc/testsuite/
	PR target/109907
	* gcc.target/avr/pr109907.c: New test.
	* gcc.target/avr/torture/pr109907-1.c: New test.
	* gcc.target/avr/torture/pr109907-2.c: New test.