Support new interrupt handler options.

Support new interrupt handler options.

gcc/
	* config/mips/mips.c (mips_int_mask): New enum.
	(mips_shadow_set): Likewise.
	(int_mask): New variable.
	(use_shadow_register_set_p): Change type to enum mips_shadow_set.
	(machine_function): Add int_mask and use_shadow_register_set.
	(mips_attribute_table): Add attribute handlers for interrupt and
	use_shadow_register_set.
	(mips_interrupt_mask): New static function.
	(mips_handle_interrupt_attr): Likewise.
	(mips_handle_use_shadow_register_set_attr): Likewise.
	(mips_use_shadow_register_set): Change return type to enum
	mips_shadow_set.  Add argument handling for use_shadow_register_set
	attribute.
	(mips_interrupt_extra_called_saved_reg_p): Update the conditional to
	compare with mips_shadow_set enum.
	(mips_compute_frame_info): Add interrupt mask and
	use_shadow_register_set to per-function information structure.
	Add a stack slot for EPC unconditionally.
	(mips_expand_prologue): Compare use_shadow_register_set value
	with mips_shadow_set enum.  Save EPC always in K1, clobber only K1 for
	masked interrupt register but in EIC mode use K0 and save Cause in K0.
	EPC saved and restored unconditionally.  Use PMODE_INSN macro when
	copying the stack pointer from the shadow register set.
	* config/mips/mips.h (SR_IM0): New define.
	* config/mips/mips.md (mips_rdpgpr): Rename to...
	(mips_rdpgpr_<mode>): ...this.  Use the Pmode iterator.
	* doc/extend.texi (Declaring Attributes of Functions): Document
	optional arguments for interrupt and use_shadow_register_set
	attributes.

gcc/testsuite/
	* gcc.target/mips/interrupt_handler-4.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@225819 138bc75d-0d04-0410-961f-82ee72b054a4