[11/77] Add a float_mode_for_size helper function

[Jeff Law]

On 07/13/2017 02:42 AM, Richard Sandiford wrote:
> This provides a type-safe way to ask for a float mode and get it as a
> scalar_float_mode.
> 
> 2017-07-13  Richard Sandiford  <richard.sandiford@linaro.org>
> 	    Alan Hayward  <alan.hayward@arm.com>
> 	    David Sherwood  <david.sherwood@arm.com>
> 
> gcc/
> 	* coretypes.h (opt_scalar_float_mode): New typedef.
> 	* machmode.h (float_mode_for_size): New function.
> 	* emit-rtl.c (double_mode): Delete.
> 	(init_emit_once): Use float_mode_for_size.
> 	* stor-layout.c (layout_type): Likewise.
> 	* gdbhooks.py (build_pretty_printer): Handle opt_scalar_float_mode.
OK.
jeff