i386.opt (-mstackrealign): New flag.

i386.opt (-mstackrealign): New flag.

        * gcc/config/i386/i386.opt (-mstackrealign): New flag.  *
	gcc/config/i386/i386.c (force_align_arg_pointer): New attribute.
	(ix86_handle_cconv_attribute): Emit error when
	force_align_arg_pointer attribute collides with too many regparms.
	(ix86_function_regparm): Limit regparms when used with
	force_align_arg_pointer attribute.  (ix86_internal_arg_pointer):
	Support stack-realigning prologue in non-main functions.  Emit
	warning for nested functions under -mstackrealign, emit error for
	nested functions with force_align_arg_pointer attribute.
	* gcc/doc/extend.texi (force_align_arg_pointer): Document it.
	* gcc/doc/invoke.texi (-mstackrealign): Document it.
	* testsuite/gcc.target/i386/20060512-1.c: New.
	* testsuite/gcc.target/i386/20060512-2.c: New.
	* testsuite/gcc.target/i386/20060512-3.c: New.
	* testsuite/gcc.target/i386/20060512-4.c: New.

From-SVN: r113880