Improve stack adjustment by reusing a temporary move immediate from the epilog

Improve stack adjustment by reusing a temporary move immediate from the epilog
if the register is still valid in the epilog.  This generates smaller code for
leaf functions with a stack size of more then 4KB.

gcc/
	* config/aarch64/aarch64.c (aarch64_add_constant_internal):
	Add extra argument to allow emitting the move immediate.
	Use add/sub with positive immediate.
	(aarch64_add_constant): Add inline function.
	(aarch64_add_sp): Likewise.
	(aarch64_sub_sp): Likewise.
	(aarch64_expand_prologue): Call aarch64_sub_sp.
	(aarch64_expand_epilogue): Call aarch64_add_sp.
	Decide when to leave out move.
	(aarch64_output_mi_thunk): Call aarch64_add_constant.

testsuite/
	* gcc.target/aarch64/test_frame_17.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@241420 138bc75d-0d04-0410-961f-82ee72b054a4