choose_hard_reg_mode previously took a boolean saying whether the
mode needed to be call-preserved.  This patch replaces it with an
optional ABI pointer instead, so that the function can use that
to test whether a value is call-saved.

default_dwarf_frame_reg_mode uses eh_edge_abi because that's the
ABI that matters for unwinding.  Targets need to override the hook
if they want something different.

2019-09-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* rtl.h (predefined_function_abi): Declare.
	(choose_hard_reg_mode): Take a pointer to a predefined_function_abi
	instead of a boolean call_save flag.
	* config/gcn/gcn.c (gcn_hard_regno_caller_save_mode): Update call
	accordingly.
	* config/i386/i386.h (HARD_REGNO_CALLER_SAVE_MODE): Likewise.
	* config/ia64/ia64.h (HARD_REGNO_CALLER_SAVE_MODE): Likewise.
	* config/mips/mips.c (mips_hard_regno_caller_save_mode): Likewise.
	* config/msp430/msp430.h (HARD_REGNO_CALLER_SAVE_MODE): Likewise.
	* config/rs6000/rs6000.h (HARD_REGNO_CALLER_SAVE_MODE): Likewise.
	* config/sh/sh.c (sh_hard_regno_caller_save_mode): Likewise.
	* reginfo.c (init_reg_modes_target): Likewise.
	(choose_hard_reg_mode): Take a pointer to a predefined_function_abi
	instead of a boolean call_save flag.
	* targhooks.c: Include function-abi.h.
	(default_dwarf_frame_reg_mode): Update call to choose_hard_reg_mode,
	using eh_edge_abi to choose the mode.

From-SVN: r276312