IA MCU psABI support: GCC changes

IA MCU psABI support: GCC changes

This patch introduces basic IA MCU psABI support into GCC.

	* configure.ac (ospace_frag): Enable for i?86*-*-elfiamcu
	target.
	* configure: Regenerate.

gcc/

	* config.gcc: Support i[34567]86-*-elfiamcu target.
	* config/i386/iamcu.h: New.
	* config/i386/i386.opt: Add -miamcu.
	* doc/invoke.texi: Document -miamcu.
	* common/config/i386/i386-common.c  (ix86_handle_option): Turn
	off x87/MMX/SSE/AVX codegen for -miamcu.
	* config/i386/i386-c.c (ix86_target_macros_internal): Define
	__iamcu/__iamcu__ for -miamcu.
	* config/i386/i386.h (PREFERRED_STACK_BOUNDARY_DEFAULT): Set
	to MIN_STACK_BOUNDARY if TARGET_IAMCU is true.
	(BIGGEST_ALIGNMENT): Set to 32 if TARGET_IAMCU is true.
	* config/i386/i386.c (ix86_option_override_internal): Ignore and
	warn -mregparm for Intel MCU.  Turn on -mregparm=3 for Intel
	MCU by default.  Default long double to 64-bit for Intel MCU.
	Turn on -freg-struct-return for Intel MCU.  Issue an error when
	-miamcu is used in 64-bit or x32 mode or if x87, MMX, SSE or
	AVX is turned on.
	(function_arg_advance_32): Pass value whose size is no larger
	than 8 bytes in registers for Intel MCU.
	(function_arg_32): Likewise.
	(ix86_return_in_memory): Return value whose size is no larger
	than 8 bytes in registers for Intel MCU.
	(iamcu_alignment): New function.
	(ix86_data_alignment): Call iamcu_alignment if TARGET_IAMCU is
	true.
	(ix86_local_alignment): Don't increase alignment for Intel MCU.
	(x86_field_alignment): Return iamcu_alignment if TARGET_IAMCU is
	true.

From-SVN: r225197