Add a no_register_allocation target hook.

Add a no_register_allocation target hook.

	* target.def (no_register_allocation): New data hook.
	* doc/tm.texi.in: Add @hook TARGET_NO_REGISTER_ALLOCATION.
	* doc/tm.texi: Regenerate.
	* ira.c (gate_ira): New function.
	(pass_data_ira): Set has_gate.
	(pass_ira): Add a gate function.
	(pass_data_reload): Likewise.
	(pass_reload): Add a gate function.
	(pass_ira): Use it.
	* reload1.c (eliminate_regs): If reg_eliminate_is NULL, assert that
	no register allocation happens on the target and return.
	* final.c (alter_subreg): Ensure register is not a pseudo before
	calling simplify_subreg.
	(output_operand): Assert that x isn't a pseudo only if doing
	register allocation.

From-SVN: r217122