re PR rtl-optimization/38711 (ira should not be using df-lr except at -O1.)

re PR rtl-optimization/38711 (ira should not be using df-lr except at -O1.)

	PR rtl-optimization/38711
	* ira.c (ira): Remove DF_LIVE if the problem is in the stack.
	(do_reload): Add it back at the end for -O2 and higher.

	* function.c (thread_prologue_and_epilogue_insns): Use
	REG_SET_TO_HARD_REG_SET instead of CLEAR_HARD_REG_SET and
	reg_set_to_hard_reg_set.

From-SVN: r192890