reload.c: (find_reloads): Skip alternatives according to the "enabled" attribute.

reload.c: (find_reloads): Skip alternatives according to the "enabled" attribute.

2008-05-27  Andreas Krebbel  <krebbel1@de.ibm.com>

	* reload.c: (find_reloads): Skip alternatives according to the
	"enabled" attribute. Constify the constraint variable.
	* recog.c (get_attr_enabled): Add default implementation.
	(extract_insn): Set the alternative_enabled_p array
	in the recog_data struct.
	(preprocess_constraints, constrain_operands): Skip
	alternatives according to the "enabled" attribute
	* recog.h (struct recog_data): New field alternative_enabled_p.
	(skip_alternative): New inline function.
	* regclass.c: (record_operand_costs): Check the "enabled"
	attribute.
	(record_reg_classes): Skip alternative according to the
	"enabled" attribute.

	* doc/md.texi: Add documention for the "enabled" attribute.

From-SVN: r136012