LRA allows address constraints that are more relaxed than "p":

  /* Target hooks sometimes don't treat extra-constraint addresses as
     legitimate address_operands, so handle them specially.  */
  if (insn_extra_address_constraint (cn)
      && satisfies_address_constraint_p (&ad, cn))
    return change_p;

For SVE it's useful to allow the same thing for memory constraints.
The particular use case is LD1RQ, which is an SVE instruction that
addresses Advanced SIMD vector modes and that accepts some addresses
that normal Advanced SIMD moves don't.

Normally we require every memory to satisfy at least "m", which is
defined to be a memory "with any kind of address that the machine
supports in general".  However, LD1RQ is very much special-purpose:
it doesn't really have any relation to normal operations on these
modes.  Adding its addressing modes to "m" would lead to bad Advanced
SIMD optimisation decisions in passes like ivopts.  LD1RQ therefore
has a memory constraint that accepts things "m" doesn't.

2019-11-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* lra-constraints.c (valid_address_p): Take the operand and a
	constraint as argument.  If the operand is a MEM and the constraint
	is a memory constraint, check whether the eliminated form of the
	MEM already satisfies the constraint.
	(process_address_1): Update calls accordingly.

gcc/testsuite/
	* gcc.target/aarch64/sve/acle/asm/ld1rq_f16.c: Remove XFAIL.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_f32.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_f64.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_s16.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_s32.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_s64.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_u16.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_u32.c: Likewise.
	* gcc.target/aarch64/sve/acle/asm/ld1rq_u64.c: Likewise.

From-SVN: r278408