S/390: Memory constraint cleanup

S/390: Memory constraint cleanup

This fixes an issue with the long displacement memory address
constraints S and T.  These were defined to only accept long
displacement addresses.  This is wrong since a memory constraint must
not reject an address with a 0 displacement.  Reload relies on being
able to turn an invalid memory address into a valid one by reloading
the address into a base register.  The S and T constraints would
reject such an address.

This isn't really a problem for the backend since we used the
constraints with that knowledge there but it is a problem for people
writing inline assemblies.

gcc/ChangeLog:

2016-04-29  Ulrich Weigand  <uweigand@de.ibm.com>

	* config/s390/constraints.md ("U", "W"): Invoke
	s390_mem_constraint with "ZR" and "ZT".
	* config/s390/s390.c (s390_check_qrst_address): Reject invalid
	addresses when using LRA.  Accept also short displacements for S
	and T constraints.  Do not check for long displacement target for
	S and T constraints.
	(s390_mem_constraint): Remove handling of U and W constraints.
	* config/s390/s390.md (various patterns): Remove the short
	displacement constraints (Q and R) if a long displacement
	constraint is present.  Add longdisp as required CPU capability.
	* config/s390/vector.md: Likewise.
	* config/s390/vx-builtins.md: Likewise.

From-SVN: r235626