[64/77] Add a scalar_mode class

[64/77] Add a scalar_mode class

This patch adds a scalar_mode class that can hold any scalar mode,
specifically:

  - scalar integers
  - scalar floating-point values
  - scalar fractional modes
  - scalar accumulator modes
  - pointer bounds modes

To start with this patch uses this type for GET_MODE_INNER.
Later patches add more uses.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* coretypes.h (scalar_mode): New class.
	* machmode.h (scalar_mode): Likewise.
	(scalar_mode::includes_p): New function.
	(mode_to_inner): Return a scalar_mode rather than a machine_mode.
	* gdbhooks.py (build_pretty_printers): Handle scalar_mode.
	* genmodes.c (get_mode_class): Handle remaining scalar modes.
	* cfgexpand.c (expand_debug_expr): Use scalar_mode.
	* expmed.c (store_bit_field_1): Likewise.
	(extract_bit_field_1): Likewise.
	* expr.c (write_complex_part): Likewise.
	(read_complex_part): Likewise.
	(emit_move_complex_push): Likewise.
	(expand_expr_real_2): Likewise.
	* function.c (assign_parm_setup_reg): Likewise.
	(assign_parms_unsplit_complex): Likewise.
	* optabs.c (expand_binop): Likewise.
	* rtlanal.c (subreg_get_info): Likewise.
	* simplify-rtx.c (simplify_immed_subreg): Likewise.
	* varasm.c (output_constant_pool_2): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r251515