[NDS32] Refine prologue and epilogue code generation.

[NDS32] Refine prologue and epilogue code generation.

gcc/
	* config/nds32/nds32.c (nds32_compute_stack_frame,
	nds32_emit_stack_push_multiple, nds32_emit_stack_pop_multiple,
	nds32_emit_stack_v3push, nds32_emit_stack_v3pop,
	nds32_emit_adjust_frame, nds32_expand_prologue, nds32_expand_epilogue,
	nds32_expand_prologue_v3push, nds32_expand_epilogue_v3pop): Refine.
	* config/nds32/nds32.h (NDS32_FIRST_CALLEE_SAVE_GPR_REGNUM,
	NDS32_LAST_CALLEE_SAVE_GPR_REGNUM, NDS32_V3PUSH_AVAILABLE_P): New.
	* config/nds32/nds32.md (prologue, epilogue): Use macro
	NDS32_V3PUSH_AVAILABLE_P to do checking.

Co-Authored-By: Chung-Ju Wu <jasonwucj@gmail.com>
Co-Authored-By: Kito Cheng <kito.cheng@gmail.com>
From-SVN: r258442