[patch i386]: Change stack probing and allocation implementation

[Kai Tietz <ktietz70 at googlemail dot com>]

Hello,

the behavior of i386's stack allocation with probing (via ___chkstk)
has some disadvantages. First the probing code is more costy on
execution then necessary - this hits mainly win32 targets where
stack-probing is active by default for stack-allocation >= 0x1000
bytes - and it is additionally incompatible to the variant of chkstk
in msvcrt.
Additionally this new version avoids some register clobbering for
64-bit and it simplifies the prologue generation a bit.

2010-08-19  Kai Tietz

	* config/i386/cygwin.asm (___chkstk_ms): New.
	* config/i386/i386.c (override_options): Replace
	gen_allocate_stack_worker_,, by gen_allocate_stack_worker_probe_,,.
	(ix86_expand_prologue): Adjust probed stack allocation.
	* config/i386/i386.md (define_insn "allocate_stack_worker_32): Removed.
	(define_insn "allocate_stack_worker_64): Removed.
	(define_insn "allocate_stack_worker_probe_32): New.
	(define_insn "allocate_stack_worker_probe_64): New.
	(allocate_stack): Adjust probed stack allocation.


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

Regards,
Kai

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