[aarch64]: force frame pointer setup before tlsdesc call

[aarch64]: force frame pointer setup before tlsdesc call

The operation that sets up the tlsdesc register is really a function
call; as such, the frame pointer should really be correctly set up
before this happens.  However, because it does not appear as a
call_insn in the RTL the normal dependencies are not added
automatically.  We fix this by adding a USE of FP_REGNUM to prevent
migration of the frame-pointer setup past the call by the scheduler.
If a frame pointer is not being used, this is harmless since it only
represents a scheduling constraint.

2019-07-03  Sylvia Taylor  <sylvia.taylor@arm.com>

	* config/aarch64/aarch64.md (FP_REGNUM): New constant.
	(tlsdesc_small_advsimd_<mode>): Add use of FP_REGNUM.
	(tlsdesc_small_sve_<mode>): Likewise.

From-SVN: r273000