re PR target/83712 ("Unable to find a register to spill" when compiling for thumb1)

re PR target/83712 ("Unable to find a register to spill" when compiling for thumb1)

2018-03-09  Vladimir Makarov  <vmakarov@redhat.com>

	PR target/83712
	* lra-assigns.c (assign_by_spills): Return a flag of reload
	assignment failure.  Do not process the reload assignment
	failures.  Do not spill other reload pseudos if they has the same
	reg class.
	(lra_assign): Add a return arg.  Set up from the result of
	assign_by_spills call.
	(find_reload_regno_insns, lra_split_hard_reg_for): New functions.
	* lra-constraints.c (split_reg): Add a new arg.  Use it instead of
	usage_insns if it is not NULL.
	(spill_hard_reg_in_range): New function.
	(split_if_necessary, inherit_in_ebb): Pass a new arg to split_reg.
	* lra-int.h (spill_hard_reg_in_range, lra_split_hard_reg_for): New
	function prototypes.
	(lra_assign): Change prototype.
	* lra.c (lra): Add code to deal with fails by splitting hard reg
	live ranges.

2018-03-09  Vladimir Makarov  <vmakarov@redhat.com>

	PR target/83712
	* gcc.target/arm/pr83712.c: New.

From-SVN: r258390