[patch i386 windows]: Introduce call-abi for 32-bit mingw and make callee_pop_aggregate_return attribute by default on for 32-bit mingw target

[Kai Tietz <ktietz70 at googlemail dot com>]

Hi,

this patch introduces for windows 32-bit target also the call-abi
specifiers (ms_abi/sys_v) and set its default for this target to
"ms_abi".  This patch set the default of the
"callee_pop_aggregate_return" attribute to true for MS_ABI call-abi on
32-bit.  Additionally it avoids the check of
"callee_pop_aggregate_return" for any x86_64 target.
I didn't changed here by intention the default settings of
cygwin-target. But of course, if wished this change could be done as
follow-up patch.

ChangeLog gcc/

2011-03-24  Kai Tietz

	* config/i386/cygming.h (DWARF_FRAME_REGISTERS): Adjust comment.
	(STACK_BOUNDARY): Check for bit-ness in case of MS_ABI.
	* config/i386/i386.c (ix86_conditional_register_usage): Adjust
	comment and use macro TARGET_64BIT_MS_ABI instead.
	(ix86_keep_aggregate_return_pointer): Optimize for 64-bit case
	and change default behavior for 32-bit MS_ABI.
	(ix86_reg_parm_stack_space): Check additionally for bit-ness.
	(ix86_function_type_abi): Allow check for ms_abi/sysv_abi for
	32-bit, too.
	(ix86_cfun_abi): Likewise.
	(ix86_maybe_switch_abi): Adjust comment.
	(init_cumulative_args): Check for bit-ness in MS_ABI case.
	(ix86_gimplify_va_arg): Check just for not TARGET_64BIT_MS_ABI
	instead of checking for SYSV_ABI.
	(ix86_nsaved_sseregs): Likewise.
	(ix86_compute_frame_layout): Set only for 64-bit MS_ABI alignment
	to 16 bytes.
	(ix86_expand_call): Use TARGET_64BIT_MS_ABI macro.
	* config/i386.h (TARGET_32BIT_MS_ABI): New macro.
	(ACCUMULATE_OUTGOING_ARGS): Check explicit for 64-bit MS_ABI.
	(OUTGOING_REG_PARM_STACK_SPACE): Likewise.
	* config/mingw32.h (DEFAULT_ABI): Change default always to MS_ABI.

Tested for x86_64-w64-mingw32, i686-pc-cygwin, and i686-w64-mingw32.
Ok for apply?

Regards,
Kai