re PR target/42895 (Low registers are preferred than register ip in thumb2 mode)

re PR target/42895 (Low registers are preferred than register ip in thumb2 mode)

	PR target/42895
	* doc/tm.texi (ADJUST_REG_ALLOC_ORDER): Renamed from
	ORDER_REGS_FOR_LOCAL_ALLOC.  All instances of this macro changed.
	(HONOR_REG_ALLOC_ORDER): Describe new macro.
	* ira.c (setup_alloc_regs): Use ADJUST_REG_ALLOC_ORDER if defined.
	* ira-color.c (assign_hard_reg): Take prologue/epilogue costs into
	account only if HONOR_REG_ALLOC_ORDER is not defined.
	* config/arm/arm.h (HONOR_REG_ALLOC_ORDER): Define.
	* system.h (ORDER_REGS_FOR_LOCAL_ALLOC): Poison.

From-SVN: r158911