gas/

gas/

	* config/tc-aarch64.c (set_other_error): New function.
	(parse_sys_reg): Add new parameter 'sys_reg' and if non-NULL set
	the variable to which it points with 'o'.
	(parse_operands): Update; check for write to read-only system
	registers or read from write-only ones.

gas/testsuite/

	* gas/aarch64/diagnostic.s: Add tests.
	* gas/aarch64/diagnostic.l: Update.
	* gas/aarch64/tracereg-illegal.d: New file.
	* gas/aarch64/tracereg-illegal.l: Ditto.
	* gas/aarch64/tracereg-illegal.s: Ditto.
	* gas/aarch64/tracereg.d: Ditto.
	* gas/aarch64/tracereg.s: Ditto.

include/opcode

	* aarch64.h (aarch64_sys_reg_readonly_p): New declaration.
	(aarch64_sys_reg_writeonly_p): Ditto.

opcodes/

	* aarch64-opc.c (CPENT): New define.
	(F_READONLY, F_WRITEONLY): Likewise.
	(aarch64_sys_regs): Add trace unit registers.
	(aarch64_sys_reg_readonly_p): New function.
	(aarch64_sys_reg_writeonly_p): Ditto.